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[[File:Batch reactor STR.svg|80px|thumb|Batch reactor symbol]] |
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{{short description|Partial intermolecular bonding interaction}} |
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The '''batch reactor''' is the generic term for a type of [[Chemical reactor|vessel]] widely used in the [[Process industry|process industries]]. Its name is something of a [[misnomer]] since vessels of this type are used for a variety of process operations such as [[Dissolution (chemistry)|solids dissolution]], [[Mixing (process engineering)|product mixing]], [[chemical reaction]]s, [[batch distillation]], [[crystallization]], liquid/liquid extraction and [[polymerization]]. In some cases, they are not referred to as [[Chemical reactor|reactors]] but have a name which reflects the role they perform (such as [[crystallizer]], or [[bioreactor]]). |
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[[Image:3D model hydrogen bonds in water.svg|right|thumb|Model of hydrogen bonds (1) between molecules of [[Properties of water|water]]]] |
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[[File:NTCDI AFM2a.jpg|thumb|[[Non-contact atomic force microscopy|AFM]] image of [[napthalenetetracarboxylic diimide]] molecules on silver-terminated silicon, interacting via hydrogen bonding, taken at 77 K.<ref>{{cite journal|doi=10.1038/ncomms4931|title=Mapping the force field of a hydrogen-bonded assembly|journal=Nature Communications|volume=5|pages=3931|year=2014|last1=Sweetman|first1=A. M.|last2=Jarvis|first2=S. P.|last3=Sang|first3=Hongqian|last4=Lekkas|first4=I.|last5=Rahe|first5=P.|last6=Wang|first6=Yu|last7=Wang|first7=Jianbo|last8=Champness|first8=N.R.|last9=Kantorovich|first9=L.|last10=Moriarty|first10=P.|bibcode=2014NatCo...5.3931S|pmid=24875276|pmc=4050271}}</ref> ("Hydrogen bonds" in the top image are exaggerated by artifacts of the imaging technique.<ref>{{Cite journal|last1=Hapala|first1=Prokop|last2=Kichin|first2=Georgy|last3=Wagner|first3=Christian|last4=Tautz|first4=F. Stefan|last5=Temirov|first5=Ruslan|last6=Jelínek|first6=Pavel|date=2014-08-19|title=Mechanism of high-resolution STM/AFM imaging with functionalized tips|journal=Physical Review B|volume=90|issue=8|pages=085421|doi=10.1103/PhysRevB.90.085421|arxiv=1406.3562|bibcode=2014PhRvB..90h5421H|s2cid=53610973}}</ref><ref>{{Cite journal|last1=Hämäläinen|first1=Sampsa K.|last2=van der Heijden|first2=Nadine|last3=van der Lit|first3=Joost|last4=den Hartog|first4=Stephan|last5=Liljeroth|first5=Peter|last6=Swart|first6=Ingmar|date=2014-10-31|title=Intermolecular Contrast in Atomic Force Microscopy Images without Intermolecular Bonds|journal=Physical Review Letters|volume=113|issue=18|pages=186102|doi=10.1103/PhysRevLett.113.186102|pmid=25396382|url=http://dspace.library.uu.nl:8080/handle/1874/307996|bibcode=2014PhRvL.113r6102H|url-status=dead|archive-url=https://web.archive.org/web/20180120232850/http://dspace.library.uu.nl:8080/handle/1874/307996|archive-date=2018-01-20|arxiv=1410.1933|hdl=1874/307996|s2cid=8309018|access-date=2017-08-30}}</ref>)]] |
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A typical batch reactor consists of a [[storage tank]] with an [[Agitator (device)|agitator]] and integral heating/cooling system. These vessels may vary in size from less than 1 litre to more than 15,000 litres. They are usually fabricated in [[steel]], [[stainless steel]], [[glass-lined steel]], [[glass]] or exotic [[alloy]]. [[Liquid]]s and [[solid]]s are usually charged via connections in the top cover of the reactor. Vapors and [[gases]] also discharge through connections in the top. Liquids are usually discharged out of the bottom. |
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A '''hydrogen bond''' (or '''H-bond''') is a primarily [[Electrostatics|electrostatic]] force of attraction between a [[hydrogen]] (H) atom which is [[Covalent bond|covalently bound]] to a more [[electronegativity|electronegative]] atom or group, and another electronegative atom bearing a [[lone pair]] of electrons—the hydrogen bond acceptor (Ac). Such an interacting system is generally denoted Dn–H···Ac, where the solid line denotes a polar [[covalent bond]], and the dotted or dashed line indicates the hydrogen bond.<ref name=":0">{{Cite journal|last1=Arunan|first1=Elangannan|last2=Desiraju|first2=Gautam R.|last3=Klein|first3=Roger A.|last4=Sadlej|first4=Joanna|last5=Scheiner|first5=Steve|last6=Alkorta|first6=Ibon|last7=Clary|first7=David C.|last8=Crabtree|first8=Robert H.|last9=Dannenberg|first9=Joseph J.|date=2011-07-08|title=Definition of the hydrogen bond (IUPAC Recommendations 2011)|url=http://www.degruyter.com/view/j/pac.2011.83.issue-8/pac-rec-10-01-02/pac-rec-10-01-02.xml|journal=Pure and Applied Chemistry|volume=83|issue=8|pages=1637–1641|doi=10.1351/PAC-REC-10-01-02|s2cid=97688573|issn=1365-3075}}</ref> The most frequent donor and acceptor atoms are the second-row elements [[nitrogen]] (N), [[oxygen]] (O), and [[fluorine]] (F) |
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The advantages of the batch reactor lie with its versatility. A single vessel can carry out a sequence of different operations without the need to break containment. This is particularly useful when processing [[toxic]] or highly [[wikt:potency|potent]] [[Chemical compound|compound]]s. |
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Hydrogen bonds can be [[intermolecular]] (occurring between separate molecules) or [[Intramolecular force|intramolecular]] (occurring among parts of the same molecule).<ref>Pimentel, G. ''The Hydrogen Bond'' Franklin Classics, 2018), {{ISBN|0343171600}}</ref><ref>Jeffrey, G. A.; ''An introduction to hydrogen bonding''; Oxford university press New York, 1997. {{ISBN|0195095499}}</ref><ref>Jeffrey, G. A.; Saenger, W. ''Hydrogen bonding in biological structures''; Springer: Berlin, '''1994, 2012''' Springer; {{ISBN|3540579036}}</ref><ref>{{GoldBookRef|file = H02899|title = hydrogen bond}}</ref> The energy of a hydrogen bond depends on the geometry, the environment, and the nature of the specific donor and acceptor atoms, and can vary between 1 and 40 kcal/mol.<ref name="The Hydrogen Bond in the Solid Stat">{{cite journal|title = The Hydrogen Bond in the Solid State|journal = [[Angew. Chem. Int. Ed.]]|year = 2002|volume = 41|pages = 48–76|doi = 10.1002/1521-3773(20020104)41:1<48::AID-ANIE48>3.0.CO;2-U |last1 = Steiner|first1 = Thomas|issue = 1|pmid = 12491444}}</ref> This makes them somewhat stronger than a [[van der Waals force|van der Waals interaction]], and weaker than fully [[covalent bond|covalent]] or [[ionic bond]]s. This type of bond can occur in inorganic molecules such as water and in [[organic molecules]] like DNA and proteins. Hydrogen bonds are responsible for holding such materials as [[paper]] and [[wool|felted wool]] together, and for causing separate sheets of paper to stick together after becoming wet and subsequently drying. |
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==Agitation== |
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The hydrogen bond is responsible for many of the anomalous physical and chemical properties of compounds of N, O, and F. In particular, intermolecular hydrogen bonding is responsible for the high boiling point of [[water]] (100 °C) compared to the other [[Hydrogen chalcogenide|group-16 hydride]]s that have much weaker hydrogen bonds.<ref>{{cite journal|journal=J. Am. Chem. Soc. |volume=93|issue=15|pages=3613–3620|author1=Sabin, John R. |title=Hydrogen bonds involving sulfur. I. Hydrogen sulfide dimer|doi=10.1021/ja00744a012|year=1971}}</ref> Intramolecular hydrogen bonding is partly responsible for the [[secondary structure|secondary]] and [[tertiary structure|tertiary]] structures of [[protein]]s and [[nucleic acid]]s. It also plays an important role in the structure of [[polymer]]s, both synthetic and natural. |
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The usual agitator arrangement is a centrally mounted [[driveshaft]] with an overhead drive unit. [[Impeller]] blades are mounted on the shaft. A wide variety of blade designs are used and typically the blades cover about two thirds of the diameter of the reactor. Where viscous products are handled, [[anchor]] shaped paddles are often used which have a close clearance between the blade and the vessel walls. |
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==Bonding== |
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[[Image:Hydrogen Bond Quadruple AngewChemIntEd 1998 v37 p75.jpg|thumb|300px|An example of [[intermolecular]] hydrogen bonding in a [[molecular self-assembly|self-assembled]] dimer complex.<ref>{{cite journal| journal=[[Angew. Chem. Int. Ed.]] |title= Self-Complementarity Achieved through Quadruple Hydrogen Bonding| year= 1998|volume=37|issue=1–2 |pages= 75–78| doi=10.1002/(SICI)1521-3773(19980202)37:1/2<75::AID-ANIE75>3.0.CO;2-R|last1= Beijer|first1= Felix H.|last2= Kooijman|first2= Huub|last3= Spek|first3= Anthony L.|last4= Sijbesma|first4= Rint P.|last5= Meijer|first5= E. W.}}</ref> The hydrogen bonds are represented by dotted lines.]] |
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[[File:Acetylacetone tautomerism.svg|thumb|300x300px|[[Intramolecular force|Intramolecular]] hydrogen bonding in [[acetylacetone]] helps stabilize the [[enol]] [[tautomer]].]] |
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Most batch reactors also use [[Baffle (in vessel)|baffles]]. These are stationary blades which break up flow caused by the rotating agitator. These may be fixed to the vessel cover or mounted on the interior of the side walls. |
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===Definitions and general characteristics=== |
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A hydrogen atom attached to a relatively [[electronegativity|electronegative]] atom is the hydrogen bond ''donor''.<ref>{{cite book|last = Campbell|first = Neil A.|author2 = Brad Williamson|author3 = Robin J. Heyden|title = Biology: Exploring Life|publisher = Pearson Prentice Hall|year = 2006|location = Boston, Massachusetts|url = http://www.phschool.com/el_marketing.html|isbn = 978-0-13-250882-7|url-status = dead|archive-url = https://web.archive.org/web/20141102041816/http://www.phschool.com/el_marketing.html|archive-date = 2014-11-02|access-date = 2008-11-11}}</ref> C-H bonds only participate in hydrogen bonding when the carbon atom is bound to electronegative substituents, as is the case in [[chloroform]], CHCl<sub>3</sub>.<ref>{{cite journal|author1=Wiley, G.R. |author2=Miller, S.I. |doi=10.1021/ja00765a001|title=Thermodynamic parameters for hydrogen bonding of chloroform with Lewis bases in cyclohexane. Proton magnetic resonance study|year=1972|journal=Journal of the American Chemical Society|volume=94|issue=10|pages=3287}}</ref> In a hydrogen bond, the electronegative atom not covalently attached to the hydrogen is named proton acceptor, whereas the one covalently bound to the hydrogen is named the proton donor. While this nomenclature is recommended by the IUPAC,<ref name=":0">{{Cite journal|last1=Arunan|first1=Elangannan|last2=Desiraju|first2=Gautam R.|last3=Klein|first3=Roger A.|last4=Sadlej|first4=Joanna|last5=Scheiner|first5=Steve|last6=Alkorta|first6=Ibon|last7=Clary|first7=David C.|last8=Crabtree|first8=Robert H.|last9=Dannenberg|first9=Joseph J.|date=2011-07-08|title=Definition of the hydrogen bond (IUPAC Recommendations 2011)|url=http://www.degruyter.com/view/j/pac.2011.83.issue-8/pac-rec-10-01-02/pac-rec-10-01-02.xml|journal=Pure and Applied Chemistry|volume=83|issue=8|pages=1637–1641|doi=10.1351/PAC-REC-10-01-02|s2cid=97688573|issn=1365-3075}}</ref> it can be misleading, since in other donor-acceptor bonds, the donor/acceptor assignment is based on the source of the electron pair (such nomenclature is also used for hydrogen bonds by some authors<ref name="The Hydrogen Bond in the Solid Stat"/>). In the hydrogen bond donor, the H center is protic. The donor is a Lewis base. Hydrogen bonds are represented as H···Y system, where the dots represent the hydrogen bond. Liquids that display hydrogen bonding (such as water) are called '''associated liquids'''. |
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[[File:H-donor-acceptor.svg|alt=|thumb|320x320px|Examples of hydrogen bond donating (donors) and hydrogen bond accepting groups (acceptors)]] |
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[[File:Acetic Acid Hydrogenbridge V.1.svg|thumb|300px|Cyclic dimer of acetic acid; dashed <span style="color:green;">'''green'''</span> lines represent hydrogen bonds]] |
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Despite significant improvements in agitator blade and baffle design, mixing in large batch reactors is ultimately constrained by the amount of [[energy]] that can be applied. On large vessels, mixing energies of more than 5 Watts per litre can put an unacceptable burden on the cooling system. High agitator loads can also create shaft stability problems. Where mixing is a critical parameter, the batch reactor is not the ideal solution. Much higher mixing rates can be achieved by using smaller flowing systems with high speed agitators, [[Ultrasound|ultrasonic]] mixing or [[static mixer]]s. |
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The hydrogen bond is often described as an [[electrostatic]] [[dipole-dipole interaction]]. However, it also has some features of [[covalent bond]]ing: it is directional and strong, produces interatomic distances shorter than the sum of the van der Waals radii, and usually involves a limited number of interaction partners, which can be interpreted as a type of [[Valence (chemistry)|valence]]. These covalent features are more substantial when acceptors bind hydrogens from more electronegative donors. |
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==Heating and cooling systems== |
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As part of a more detailed list of criteria, the IUPAC publication acknowledges that the attractive interaction can arise from some combination of electrostatics (multipole-multipole and multipole-induced multipole interactions), covalency (charge transfer by orbital overlap), and dispersion (London forces), and states that the relative importance of each will vary depending on the system. However, a footnote to the criterion recommends the exclusion of interactions in which dispersion is the primary contributor, specifically giving Ar---CH<sub>4</sub> and CH<sub>4</sub>---CH<sub>4</sub> as examples of such interactions to be excluded from the definition.<ref name=":0" /> |
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Nevertheless, most introductory textbooks still restrict the definition of hydrogen bond to the "classical" type of hydrogen bond characterized in the opening paragraph. |
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Products within batch reactors usually liberate or absorb [[heat]] during processing. Even the action of stirring stored liquids generates heat. In order to hold the reactor contents at the desired [[temperature]], heat has to be added or removed by a [[heat exchanger|cooling jacket]] or [[heat pipe|cooling pipe]]. Heating/cooling coils or external jackets are used for heating and cooling batch reactors. Heat transfer fluid passes through the jacket or coils to add or remove heat. |
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Weaker hydrogen bonds<ref>Desiraju, G. R. and Steiner, T. The Weak Hydrogen Bond: In Structural Chemistry and Biology , International Union of Crystallography;'''2001''', {{ISBN|0198509707}}</ref> are known for hydrogen atoms bound to elements such as sulfur (S) or chlorine (Cl); even carbon (C) can serve as a donor, particularly when the carbon or one of its neighbors is electronegative (e.g., in chloroform, aldehydes and terminal acetylenes).<ref>Nishio, M.; Hirota, M.; Umezawa, Y. ''The CH–π Interactions''; Wiley-VCH, New York, 1998. • Wiley-VCH; 1998) {{ISBN|0471252905}}</ref><ref>{{cite journal | last1 = Nishio | first1 = M | year = 2011 | title = The CH/[small pi] hydrogen bond in chemistry. "Title | journal = Phys. Chem. Chem. Phys. | volume = 13 | issue = 31 | pages = 13873–13900 | doi=10.1039/c1cp20404a| pmid = 21611676 }}</ref> Gradually, it was recognized that there are many examples of weaker hydrogen bonding involving donor other than N, O, or F and/or acceptor Ac with electronegativity approaching that of hydrogen (rather than being much more electronegative). Though these "non-traditional" hydrogen bonding interactions are often quite weak (~1 kcal/mol), they are also ubiquitous and are increasingly recognized as important control elements in receptor-ligand interactions in medicinal chemistry or intra-/intermolecular interactions in materials sciences. |
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Within the chemical and [[pharmaceutical]] industries, external cooling jackets are generally preferred as they make the vessel easier to clean. The performance of these jackets can be defined by 3 parameters: |
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The definition of hydrogen bonding has gradually broadened over time to include these weaker attractive interactions. In 2011, an [[IUPAC]] Task Group recommended a modern evidence-based definition of hydrogen bonding, which was published in the [[IUPAC]] journal ''[[Pure and Applied Chemistry]]''. This definition specifies: |
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* response time to modify the jacket temperature |
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{{quote|The hydrogen bond is an attractive interaction between a hydrogen atom from a molecule or a molecular fragment X–H in which X is more electronegative than H, and an atom or a group of atoms in the same or a different molecule, in which there is evidence of bond formation.<ref name="arunen2011">{{cite journal|title = Definition of the hydrogen bond|journal = [[Pure Appl. Chem.]]|year = 2011|volume = 83|issue = 8|pages = 1637–1641|doi = 10.1351/PAC-REC-10-01-02 |last1 = Arunan|first1 = Elangannan|last2 = Desiraju|first2 = Gautam R.|last3 = Klein|first3 = Roger A.|last4 = Sadlej|first4 = Joanna|last5 = Scheiner|first5 = Steve|last6 = Alkorta|first6 = Ibon|last7 = Clary|first7 = David C.|last8 = Crabtree|first8 = Robert H.|last9 = Dannenberg|first9 = Joseph J.|last10 = Hobza|first10 = Pavel|last11 = Kjaergaard|first11 = Henrik G.|last12 = Legon|first12 = Anthony C.|last13 = Mennucci|first13 = Benedetta|last14 = Nesbitt|first14 = David J.|s2cid = 97688573}}</ref>}} |
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* [[wikt:Uniformity|uniformity]] of jacket temperature |
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* [[wikt:Stability|stability]] of jacket temperature. |
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It can be argued that [[heat transfer coefficient]] is also an important parameter. It has to be recognized however that large batch reactors with external cooling jackets have severe heat transfer constraints by virtue of design. It is difficult to achieve better than 100 Watts/litre even with ideal heat transfer conditions. By contrast, [[Continuous flow reactor|continuous reactors]] can deliver cooling capacities in excess of 10,000 [[watt|W]]/[[litre]]. For processes with very high heat loads, there are better solutions than batch reactors. |
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===Bond strength=== |
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Hydrogen bonds can vary in strength from weak (1–2 kJ mol<sup>−1</sup>) to strong (161.5 kJ mol<sup>−1</sup> in the ion {{chem|link=Bifluoride|HF|2|-}}).<ref name=halide>{{cite journal|doi=10.1021/ic00182a010|title=Gas-phase bihalide and pseudobihalide ions. An ion cyclotron resonance determination of hydrogen bond energies in XHY- species (X, Y = F, Cl, Br, CN)|year=1984|last1=Larson|first1=J. W.|last2=McMahon|first2=T. B.|journal=Inorganic Chemistry|volume=23|issue=14|pages=2029–2033|title-link=ion cyclotron resonance}}</ref><ref>{{cite journal|author = Emsley, J.|title = Very Strong Hydrogen Bonds|journal = [[Chemical Society Reviews]]|year = 1980|volume = 9|issue = 1|pages = 91–124|doi = 10.1039/cs9800900091}}</ref> Typical [[Enthalpy|enthalpies]] in vapor include:<ref>V. David, N. Grinberg, S. C. Moldoveanu in ''Advances in Chromatography Volume 54'' (Eds.: E. Grushka, N. Grinberg), CRC Press, Boca Raton, '''2018''', chapter 3.</ref> |
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* F−H···:F (161.5 kJ/mol or 38.6 kcal/mol), illustrated uniquely by HF<sub>2</sub><sup>−</sup>, [[bifluoride]] |
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* O−H···:N (29 kJ/mol or 6.9 kcal/mol), illustrated water-ammonia |
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* O−H···:O (21 kJ/mol or 5.0 kcal/mol), illustrated water-water, alcohol-alcohol |
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* N−H···:N (13 kJ/mol or 3.1 kcal/mol), illustrated by ammonia-ammonia |
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* N−H···:O (8 kJ/mol or 1.9 kcal/mol), illustrated water-amide |
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* {{chem|OH|3|+}}···:{{chem|OH|2|}} (18 kJ/mol<ref>Data obtained using [[molecular dynamics]] as detailed in the reference and should be compared to 7.9 kJ/mol for bulk water, obtained using the same calculation.{{cite journal|title = Structure and energetics of the hydronium hydration shells|author1 = Markovitch, Omer|author2 = Agmon, Noam|journal = [[J. Phys. Chem. A]]|year = 2007|volume = 111|issue = 12|pages = 2253–2256|doi = 10.1021/jp068960g|pmid = 17388314|bibcode = 2007JPCA..111.2253M|url = http://www.fh.huji.ac.il/~agmon/Fullpaper/JPCA111-2253.pdf|url-status = dead|archive-url = https://web.archive.org/web/20140813174617/http://www.fh.huji.ac.il/%7Eagmon/Fullpaper/JPCA111-2253.pdf|archive-date = 2014-08-13|citeseerx = 10.1.1.76.9448|access-date = 2017-10-25}}</ref> or 4.3 kcal/mol) |
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The strength of intermolecular hydrogen bonds is most often evaluated by measurements of equilibria between molecules containing donor and/or acceptor units, most often in solution.<ref>{{cite journal | vauthors = Biedermann F, Schneider HJ | title = Experimental Binding Energies in Supramolecular Complexes | journal = Chemical Reviews | volume = 116 | issue = 9 | pages = 5216–300 | date = May 2016 | pmid = 27136957 | doi = 10.1021/acs.chemrev.5b00583 }}</ref> The strength of intramolecular hydrogen bonds can be studied with equilibria between conformers with and without hydrogen bonds. The most important method for the identification of hydrogen bonds also in complicated molecules is [[crystallography]], sometimes also NMR-spectroscopy. Structural details, in particular distances between donor and acceptor which are smaller than the sum of the van der Waals radii can be taken as indication of the hydrogen bond strength. |
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Fast temperature control response and uniform jacket heating and cooling is particularly important for crystallization processes or operations where the product or process is very temperature sensitive. There are several types of batch reactor cooling jackets: |
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One scheme gives the following somewhat arbitrary classification: those that are 15 to 40 kcal/mol, 5 to 15 kcal/mol, and >0 to 5 kcal/mol are considered strong, moderate, and weak, respectively. |
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=== |
===Single external jacket=== |
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[[Image:Batch reactor.2.jpg|thumb|right|180px|Batch reactor with single external cooling jacket]] |
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The X−H distance is typically ≈110 [[picometre|pm]], whereas the H···Y distance is ≈160 to 200 pm. The typical length of a hydrogen bond in water is 197 pm. The ideal bond angle depends on the nature of the hydrogen bond donor. The following hydrogen bond angles between a hydrofluoric acid donor and various acceptors have been determined experimentally:<ref>{{cite journal|doi=10.1039/CS9871600467|title=Angular geometries and other properties of hydrogen-bonded dimers: a simple electrostatic interpretation of the success of the electron-pair model|year=1987|last1=Legon|first1=A. C.|last2=Millen|first2=D. J.|journal=Chemical Society Reviews|volume=16|pages=467}}</ref> |
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The single jacket design consists of an outer jacket which surrounds the vessel. Heat transfer fluid flows around the jacket and is injected at high [[velocity]] via nozzles. The temperature in the jacket is [[regulated]] to control heating or cooling. |
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{|class="wikitable" style="text-align:left" |
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!Acceptor···donor||VSEPR geometry||Angle (°) |
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|HCN···HF||linear||style="text-align:right"|180 |
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|H<sub>2</sub>CO···HF||trigonal planar||style="text-align:right"|120 |
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|- |
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|H<sub>2</sub>O···HF||pyramidal||style="text-align:right"|46 |
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|H<sub>2</sub>S···HF||pyramidal||style="text-align:right"|89 |
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|- |
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|SO<sub>2</sub>···HF||trigonal ||style="text-align:right"|142 |
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|} |
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The single jacket is probably the oldest design of external cooling jacket. Despite being a tried and tested solution, it has some limitations. On large vessels, it can take many minutes to adjust the temperature of the fluid in the cooling jacket. This results in sluggish temperature control. The distribution of [[heat transfer]] fluid is also far from ideal and the heating or cooling tends to vary between the side walls and bottom dish. Another issue to consider is the inlet temperature of the heat transfer fluid which can oscillate (in response to the temperature control valve) over a wide temperature range to cause hot or cold spots at the jacket inlet points. |
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===Spectroscopy=== |
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Strong hydrogen bonds are revealed by downfield shifts in the [[proton NMR spectroscopy|<sup>1</sup>H NMR spectrum]]. For example, the acidic proton in the enol tautomer of [[acetylacetone]] appears at δ<sub>H</sub> 15.5, which is about 10 ppm downfield of a conventional alcohol.<ref>Friebolin, H., "Basic One- and Two- Dimensional NMR Spectroscopy, 4th ed.," VCH: Weinheim, 2008. {{ISBN|978-3-527-31233-7}}</ref> |
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===Half coil jacket=== |
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In the IR spectrum, hydrogen bonding shifts the X-H stretching frequency to lower energy (i.e. the vibration frequency decreases). This shift reflects a weakening of the X-H bond. Certain hydrogen bonds - improper hydrogen bonds - show a blue shift of the X-H stretching frequency and a decrease in the bond length.<ref>{{cite journal |vauthors=Hobza P, Havlas Z |title=Blue-Shifting Hydrogen Bonds |journal=Chem. Rev. |volume=100 |issue=11 |pages=4253–4264 |year=2000 |doi=10.1021/cr990050q |pmid=11749346 }}</ref> H-bonds can also be measured by IR vibrational mode shifts of the acceptor. The amide I mode of backbone carbonyls in α-helices shifts to lower frequencies when they form H-bonds with side-chain hydroxyl groups.<ref name="Feldblum 2014 4085–4090">{{cite journal|last=Feldblum|first=Esther S.|author2=Arkin, Isaiah T.|title=Strength of a bifurcated H bond|journal=Proceedings of the National Academy of Sciences|volume=111|issue=11|pages=4085–4090|year=2014|doi=10.1073/pnas.1319827111|pmid=24591597|pmc=3964065|bibcode=2014PNAS..111.4085F|doi-access=free}}</ref> |
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[[Image:Final half coil vessel.JPG|thumb|right|180px|Batch reactor with half coil jacket]] |
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The half coil jacket is made by [[welding]] a half pipe around the outside of the vessel to create a semi circular flow channel. The heat transfer fluid passes through the channel in a [[plug flow]] fashion. A large reactor may use several coils to deliver the heat transfer fluid. Like the single jacket, the temperature in the jacket is regulated to control heating or cooling. |
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The plug flow characteristics of a half coil jacket permits faster displacement of the heat transfer fluid in the jacket (typically less than 60 seconds). This is desirable for good temperature control. It also provides good distribution of heat transfer fluid which avoids the problems of non uniform heating or cooling between the side walls and bottom dish. Like the single jacket design however the inlet heat transfer fluid is also vulnerable to large oscillations (in response to the temperature control valve) in temperature. |
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===Theoretical considerations=== |
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Hydrogen bonding is of persistent theoretical interest.<ref>{{ Cite journal|last1=Weinhold|first1=Frank|last2=Klein|first2=Roger A.|year=2014|volume=15|pages=276–285|title=What is a hydrogen bond? Resonance covalency in the supramolecular domain|journal=Chemistry Education Research and Practice|issue=3|doi=10.1039/c4rp00030g}}</ref> According to a modern description O:H-O integrates both the intermolecular O:H lone pair ":" nonbond and the intramolecular H-O polar-covalent bond associated with O-O repulsive coupling.<ref>{{cite book|title= The Attribute of Water: Single Notion, Multiple Myths|year= 2016|isbn=978-981-10-0178-9|author= Sun, C. Q. |author2 = Sun, Yi }}</ref> |
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===Constant flux cooling jacket=== |
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Quantum chemical calculations of the relevant interresidue potential constants (compliance constants) revealed{{how|date=December 2015}} large differences between individual H bonds of the same type. For example, the central interresidue N−H···N hydrogen bond between guanine and cytosine is much stronger in comparison to the N−H···N bond between the adenine-thymine pair.<ref>{{cite journal|doi=10.1021/ja046282a|pmid=15600318|title=Direct Assessment of Interresidue Forces in Watson−Crick Base Pairs Using Theoretical Compliance Constants|journal=Journal of the American Chemical Society|volume=126|issue=50|pages=16310–1|year=2004|last1=Grunenberg|first1=Jörg}}</ref> |
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[[Image:Coflux jacket.JPG|thumb|right|180px|Batch reactor with constant flux (Coflux) jacket]] |
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The constant flux cooling jacket is a relatively recent development. It is not a single jacket but has a series of 20 or more small jacket elements. The temperature control valve operates by opening and closing these channels as required. By varying the heat transfer area in this way, the process temperature can be regulated without altering the jacket temperature. |
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The constant flux jacket has very fast temperature control response (typically less than 5 seconds) due to the short length of the flow channels and high velocity of the heat transfer fluid. Like the half coil jacket the heating/cooling [[flux]] is uniform. Because the jacket operates at substantially constant temperature however the inlet temperature oscillations seen in other jackets are absent. An unusual feature of this type jacket is that process heat can be measured very sensitively. This allows the user to monitor the rate of reaction for detecting end points, controlling addition rates, controlling [[crystallization]] etc. |
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Theoretically, the bond strength of the hydrogen bonds can be assessed using NCI index, [[non-covalent interactions index]], which allows a visualization of these [[non-covalent interactions]], as its name indicates, using the electron density of the system. |
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===Applications=== |
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From interpretations of the [[anisotropy|anisotropies]] in the [[Compton scattering|Compton profile]] of ordinary ice that the hydrogen bond is partly covalent.<ref>{{cite journal|author=Isaacs, E.D.|journal= Physical Review Letters |doi=10.1103/PhysRevLett.82.600|title=Covalency of the Hydrogen Bond in Ice: A Direct X-Ray Measurement|year=1999|volume=82|issue=3|pages=600–603|bibcode = 1999PhRvL..82..600I |display-authors=etal}}</ref> However, this interpretation was challenged.<ref>{{Cite journal|last1=Ghanty|first1=Tapan K.|last2=Staroverov|first2=Viktor N.|last3=Koren|first3=Patrick R.|last4=Davidson|first4=Ernest R.|date=2000-02-01|title=Is the Hydrogen Bond in Water Dimer and Ice Covalent?|journal=Journal of the American Chemical Society|volume=122|issue=6|pages=1210–1214|doi=10.1021/ja9937019|issn=0002-7863}}</ref> |
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Batch reactors are often used in the process industry. Batch reactors also have many laboratory applications, such as small scale production and inducing fermentation for beverage products. They also have many uses in medical production. Batch reactors are generally considered expensive to run, as well as variable product reliability. They are also used for experiments of reaction kinetics, volatiles and thermodynamics. Batch reactors are also highly used in waste water treatment. They are effective in reducing BOD (biological oxygen demand) of influent untreated water.<ref>"The Sequencing Batch Reactor as a Powerful Tool for the Study of Slowly Growing Anaerobic Ammonium-oxidizing Microorganisms - Springer." The Sequencing Batch Reactor as a Powerful Tool for the Study of Slowly Growing Anaerobic Ammonium-oxidizing Microorganisms - Springer. N.p., 01 Nov. 1998. Web. 26 Feb. 2014.></ref><ref>"Aerobic Granulation in a Sequencing Batch Reactor." Aerobic Granulation in a Sequencing Batch Reactor. N.p., n.d. Web. 26 Feb. 2014.</ref><ref>"Water Science & Technology 27:5-6 (1993) 241-252 - T. Kuba Et Al. - Biological Phosphorus Removal from Wastewater by Anaerobic-Anoxic Sequencing Batch Reactor." Water Science & Technology 27:5-6 (1993) 241-252 - T. Kuba Et Al. - Biological Phosphorus Removal from Wastewater by Anaerobic-Anoxic Sequencing Batch Reactor. N.p., n.d. Web. 26 Feb. 2014.</ref><ref>"Aerobic Granular Sludge in a Sequencing Batch Reactor." Aerobic Granular Sludge in a Sequencing Batch Reactor. N.p., n.d. Web. 26 Feb. 2014.</ref><ref>"Sequencing Batch Reactors - Springer." Sequencing Batch Reactors - Springer. N.p., n.d. Web. 26 Feb. 2014.</ref><ref>"Sequencing Batch Reactor Technology." Google Books. N.p., n.d. Web. 26 Feb. 2014.</ref><ref>"Simultaneous Nitrification, Denitrification, and Phosphorus Removal in a Lab-scale Sequencing Batch Reactor." - Zeng. N.p., n.d. Web. 26 Feb. 2014.</ref><ref>"Nitrification, Denitrification and Biological Phosphorus Removal in Piggery Wastewater Using a Sequencing Batch Reactor." Nitrification, Denitrification and Biological Phosphorus Removal in Piggery Wastewater Using a Sequencing Batch Reactor. N.p., n.d. Web. 26 Feb. 2014.></ref> |
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Most generally, the hydrogen bond can be viewed as a [[metric (mathematics)|metric]]-dependent [[electrostatic]] [[scalar field]] between two or more intermolecular bonds. This is slightly different from the [[Intramolecular force|intramolecular]] [[bound states]] of, for example, [[covalent bond|covalent]] or [[ionic bond]]s; however, hydrogen bonding is generally still a [[bound state]] phenomenon, since the [[interaction energy]] has a net negative sum. The initial theory of hydrogen bonding proposed by [[Linus Pauling]] suggested that the hydrogen bonds had a partial covalent nature. This interpretation remained controversial until [[nuclear magnetic resonance|NMR techniques]] demonstrated information transfer between hydrogen-bonded nuclei, a feat that would only be possible if the hydrogen bond contained some covalent character.<ref>{{cite journal|title = Observation of through-hydrogen-bond (2h)J(HC') in a perdeuterated protein|journal = [[J Magn Reson]]|year = 1999|volume = 140|pages = 510–2|doi = 10.1006/jmre.1999.1899|pmid = 10497060|issue = 2|bibcode = 1999JMagR.140..510C |last1 = Cordier|first1 = F|last2 = Rogowski|first2 = M|last3 = Grzesiek|first3 = S|last4 = Bax|first4 = A|s2cid = 121429|url = https://semanticscholar.org/paper/313914f3a544c88c2fa13303a37500e9fd7a4c7c}}</ref> |
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== |
== See also == |
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The concept of hydrogen bonding once was challenging.<ref>{{cite journal|title=Hydrogen bonding: Homing in on a tricky chemical concept|author=Needham, Paul |journal=Studies in History and Philosophy of Science Part A|volume=44|year=2013|pages=51–65|doi=10.1016/j.shpsa.2012.04.001}}</ref> [[Linus Pauling]] credits T. S. Moore and T. F. Winmill with the first mention of the hydrogen bond, in 1912.<ref>{{cite book |
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|last=Pauling |first=L. |
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|title=The nature of the chemical bond and the structure of molecules and crystals; an introduction to modern structural chemistry |
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|url=https://archive.org/details/natureofchemical00paul |url-access=registration |publisher=Cornell University Press |
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|location=Ithaca (NY) |
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|year=1960 |
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|edition=3rd |
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|page=[https://archive.org/details/natureofchemical00paul/page/450 450] |
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|isbn=978-0-8014-0333-0 |
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}}</ref><ref>{{cite journal|journal=J. Chem. Soc. |volume=101|page=1635|author1=Moore, T. S.|author2=Winmill, T. F. |title=The state of amines in aqueous solution|doi=10.1039/CT9120101635|year=1912}}</ref> Moore and Winmill used the hydrogen bond to account for the fact that trimethylammonium hydroxide is a weaker base than [[tetramethylammonium hydroxide]]. The description of hydrogen bonding in its better-known setting, water, came some years later, in 1920, from [[Wendell Mitchell Latimer|Latimer]] and Rodebush.<ref>{{cite journal|doi=10.1021/ja01452a015|year=1920|last1=Latimer|first1=Wendell M.|last2=Rodebush|first2=Worth H.|journal=Journal of the American Chemical Society|volume=42|issue=7|pages=1419–1433|title=Polarity and ionization from the standpoint of the Lewis theory of valence|url=https://zenodo.org/record/1428832}}</ref> In that paper, Latimer and Rodebush cite work by a fellow scientist at their laboratory, [[Maurice Loyal Huggins]], saying, "Mr. Huggins of this laboratory in some work as yet unpublished, has used the idea of a hydrogen kernel held between two atoms as a theory in regard to certain organic compounds." |
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* [[Chemical reactor]] |
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==Hydrogen bonds in small molecules== |
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* [[Continuous reactor]] |
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[[Image:Hex ice.GIF|thumb|right|Crystal structure of hexagonal ice. Gray dashed lines indicate hydrogen bonds]] |
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[[File:NIMGLO12.png|right|thumb|120px|Structure of [[nickel bis(dimethylglyoximate)]], which features two linear hydrogen-bonds.]] |
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== |
== References == |
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<references /> |
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A ubiquitous example of a hydrogen bond is found between [[water]] molecules. In a discrete water molecule, there are two hydrogen atoms and one oxygen atom. The simplest case is a pair of [[water]] molecules with one hydrogen bond between them, which is called the [[water dimer]] and is often used as a model system. When more molecules are present, as is the case with liquid water, more bonds are possible because the oxygen of one water molecule has two lone pairs of electrons, each of which can form a hydrogen bond with a hydrogen on another water molecule. This can repeat such that every water molecule is H-bonded with up to four other molecules, as shown in the figure (two through its two lone pairs, and two through its two hydrogen atoms). Hydrogen bonding strongly affects the [[crystal structure]] of [[ice]], helping to create an open hexagonal lattice. The density of ice is less than the density of water at the same temperature; thus, the solid phase of water floats on the liquid, unlike most other substances. |
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[[Liquid]] water's high [[boiling point]] is due to the high number of hydrogen bonds each molecule can form, relative to its low [[molecular mass]]. Owing to the difficulty of breaking these bonds, water has a very high boiling point, melting point, and viscosity compared to otherwise similar liquids not conjoined by hydrogen bonds. Water is unique because its oxygen atom has two lone pairs and two hydrogen atoms, meaning that the total number of bonds of a water molecule is up to four. |
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The number of hydrogen bonds formed by a molecule of liquid water fluctuates with time and temperature.<ref name="Jorgensen1985"/> From [[water model|TIP4P]] liquid water simulations at 25 °C, it was estimated that each water molecule participates in an average of 3.59 hydrogen bonds. At 100 °C, this number decreases to 3.24 due to the increased molecular motion and decreased density, while at 0 °C, the average number of hydrogen bonds increases to 3.69.<ref name="Jorgensen1985">{{cite journal|author1=Jorgensen, W. L. |author2=Madura, J. D. | title=Temperature and size dependence for Monte Carlo simulations of TIP4P water| journal=[[Mol. Phys.]]|year=1985| volume=56 |issue=6 |pages=1381 |doi=10.1080/00268978500103111|bibcode = 1985MolPh..56.1381J }}</ref> Another study found a much smaller number of hydrogen bonds: 2.357 at 25 °C.<ref>{{cite journal|author=Zielkiewicz, Jan |title= Structural properties of water: Comparison of the SPC, SPCE, TIP4P, and TIP5P models of water| journal=[[J. Chem. Phys.]]|volume= 123|pages=104501|year=2005| doi=10.1063/1.2018637|pmid=16178604|issue=10|bibcode = 2005JChPh.123j4501Z }}</ref> The differences may be due to the use of a different method for defining and counting the hydrogen bonds. |
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Where the bond strengths are more equivalent, one might instead find the atoms of two interacting water molecules partitioned into two [[polyatomic ion]]s of opposite charge, specifically [[hydroxide]] (OH<sup>−</sup>) and [[hydronium]] (H<sub>3</sub>O<sup>+</sup>). (Hydronium ions are also known as "hydroxonium" ions.) |
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:H−O<sup>−</sup> H<sub>3</sub>O<sup>+</sup> |
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Indeed, in pure water under conditions of [[standard temperature and pressure]], this latter formulation is applicable only rarely; on average about one in every 5.5 × 10<sup>8</sup> molecules gives up a proton to another water molecule, in accordance with the value of the [[dissociation constant]] for water under such conditions. It is a crucial part of the uniqueness of water. |
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Because water may form hydrogen bonds with solute proton donors and acceptors, it may competitively inhibit the formation of solute intermolecular or intramolecular hydrogen bonds. Consequently, hydrogen bonds between or within solute molecules dissolved in water are almost always unfavorable relative to hydrogen bonds between water and the donors and acceptors for hydrogen bonds on those solutes.<ref>{{cite journal|author=Jencks, William |title= Hydrogen Bonding between Solutes in Aqueous Solution| journal=[[J. Am. Chem. Soc.]]|volume= 108|pages=4196|year=1986|issue=14|doi=10.1021/ja00274a058|last2=Jencks|first2=William P.}}</ref> Hydrogen bonds between water molecules have an average lifetime of 10<sup>−11</sup> seconds, or 10 picoseconds.<ref name="Dillon">{{cite book|last=Dillon|first=P. F.|title=Biophysics: A Physiological Approach|url=https://books.google.com/books?id=5IYKLIx-Jt4C|year=2012|publisher=Cambridge University Press|isbn=978-1-139-50462-1|page=37}}</ref> |
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=== Bifurcated and over-coordinated hydrogen bonds in water === |
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A single hydrogen atom can participate in two hydrogen bonds, rather than one. This type of bonding is called "bifurcated" (split in two or "two-forked"). It can exist, for instance, in complex natural or synthetic organic molecules.<ref>{{cite journal|doi=10.1139/v84-087|journal=Can. J. Chem.|volume= 62|issue= 3|pages= 526–530|title=Hétérocycles à fonction quinone. V. Réaction anormale de la butanedione avec la diamino-1,2 anthraquinone; structure cristalline de la naphto \2,3-f] quinoxalinedione-7,12 obtenue|year=1984|last1=Baron|first1=Michel|last2=Giorgi-Renault|first2=Sylviane|last3=Renault|first3=Jean|last4=Mailliet|first4=Patrick|last5=Carré|first5=Daniel|last6=Etienne|first6=Jean}}</ref> It has been suggested that a bifurcated hydrogen atom is an essential step in water reorientation.<ref>{{cite journal|title = A Molecular Jump Mechanism for Water Reorientation|author1=Laage, Damien |author2=Hynes, James T.|journal = [[Science (journal)|Science]]|year = 2006|volume = 311|pages = 832–5|doi = 10.1126/science.1122154|pmid = 16439623|issue = 5762|bibcode = 2006Sci...311..832L |s2cid=6707413 }}</ref><br /> |
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Acceptor-type hydrogen bonds (terminating on an oxygen's lone pairs) are more likely to form bifurcation (it is called overcoordinated oxygen, OCO) than are donor-type hydrogen bonds, beginning on the same oxygen's hydrogens.<ref>{{cite journal|title = The Distribution of Acceptor and Donor Hydrogen-Bonds in Bulk Liquid Water|author1=Markovitch, Omer |author2=Agmon, Noam |journal = Molecular Physics|year = 2008|volume = 106|issue = 2|pages = 485|doi = 10.1080/00268970701877921|bibcode = 2008MolPh.106..485M |s2cid=17648714 }}</ref> |
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===Other liquids=== |
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For example, [[hydrogen fluoride]]—which has three lone pairs on the F atom but only one H atom—can form only two bonds; ([[ammonia]] has the opposite problem: three hydrogen atoms but only one lone pair). |
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:H−F···H−F···H−F |
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===Further manifestations of solvent hydrogen bonding=== |
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* Increase in the [[melting point]], [[boiling point]], [[solubility]], and viscosity of many compounds can be explained by the concept of hydrogen bonding. |
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* Negative [[Azeotrope|azeotropy]] of mixtures of HF and water |
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* The fact that ice is less dense than liquid water is due to a crystal structure stabilized by hydrogen bonds. |
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* Dramatically higher boiling points of NH<sub>3</sub>, H<sub>2</sub>O, and HF compared to the heavier analogues PH<sub>3</sub>, H<sub>2</sub>S, and HCl, where hydrogen-bonding is absent. |
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* Viscosity of anhydrous [[phosphoric acid]] and of [[glycerol]] |
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* Dimer formation in [[carboxylic acid]]s and hexamer formation in [[hydrogen fluoride]], which occur even in the gas phase, resulting in gross deviations from the [[ideal gas law]]. |
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* Pentamer formation of water and alcohols in apolar solvents. |
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==Hydrogen bonds in polymers== |
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Hydrogen bonding plays an important role in determining the three-dimensional structures and the properties adopted by many synthetic and natural proteins. Compared to the C-C, C-O, and C-N bonds that comprise most polymers, hydrogen bonds are far weaker, perhaps 5%. Thus, hydrogen bonds can be broken by chemical or mechanical means while retaining the basic structure of the polymer backbone. This hierarchy of bond strengths (covalent bonds being stronger than hydrogen-bonds being stronger than van der Waals forces) is key to understanding the properties of many materials.<ref>{{cite book|title=Hydrogen Bonding in Polymer Materials|author=Shiao-Wei Kuo|year=2018|publisher=Wiley-VCH }}</ref> |
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===DNA=== |
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[[File:DNA animation.gif|thumb|The structure of part of a DNA [[double helix]]]] |
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[[File:Base pair GC.svg|thumb|Hydrogen bonding between [[guanine]] and [[cytosine]], one of two types of [[base pair]]s in DNA]] |
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In these macromolecules, bonding between parts of the same macromolecule cause it to fold into a specific shape, which helps determine the molecule's physiological or biochemical role. For example, the double helical structure of [[DNA]] is due largely to hydrogen bonding between its [[base pair]]s (as well as [[pi stacking]] interactions), which link one complementary strand to the other and enable [[DNA replication|replication]]. |
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===Proteins=== |
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In the [[Protein secondary structure|secondary structure of proteins]], hydrogen bonds form between the backbone oxygens and [[amide]] hydrogens. When the spacing of the [[amino acid]] residues participating in a hydrogen bond occurs regularly between positions ''i'' and ''i'' + 4, an [[alpha helix]] is formed. When the spacing is less, between positions ''i'' and ''i'' + 3, then a [[3 10 helix|3<sub>10</sub> helix]] is formed. When two strands are joined by hydrogen bonds involving alternating residues on each participating strand, a [[beta sheet]] is formed. Hydrogen bonds also play a part in forming the tertiary structure of protein through interaction of R-groups. (See also [[protein folding]]). |
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[[Bifurcated H-bond]] systems are common in alpha-helical [[transmembrane proteins]] between the backbone amide C=O of residue ''i'' as the H-bond acceptor and two H-bond donors from residue ''i+4'': the backbone amide N-H and a side-chain hydroxyl or thiol H<sup>+</sup>. The energy preference of the bifurcated H-bond hydroxyl or thiol system is -3.4 kcal/mol or -2.6 kcal/mol, respectively. This type of bifurcated H-bond provides an intrahelical H-bonding partner for polar side-chains, such as [[serine]], [[threonine]], and [[cysteine]] within the hydrophobic membrane environments.<ref name="Feldblum 2014 4085–4090"/> |
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The role of hydrogen bonds in protein folding has also been linked to osmolyte-induced protein stabilization. Protective osmolytes, such as [[trehalose]] and [[sorbitol]], shift the protein folding equilibrium toward the folded state, in a concentration dependent manner. While the prevalent explanation for osmolyte action relies on excluded volume effects that are entropic in nature, [[circular dichroism]] (CD) experiments have shown osmolyte to act through an enthalpic effect.<ref>{{cite journal|last=Politi|first=Regina|author2=Harries, Daniel|title=Enthalpically driven peptide stabilization by protective osmolytes|journal=ChemComm|year=2010|volume=46|pages=6449–6451|doi=10.1039/C0CC01763A|pmid=20657920|issue=35}}</ref> The molecular mechanism for their role in protein stabilization is still not well established, though several mechanisms have been proposed. Computer [[molecular dynamics]] simulations suggest that osmolytes stabilize proteins by modifying the hydrogen bonds in the protein hydration layer.<ref>{{cite journal|last=Gilman-Politi|first=Regina|author2=Harries, Daniel|title=Unraveling the Molecular Mechanism of Enthalpy Driven Peptide Folding by Polyol Osmolytes|journal=Journal of Chemical Theory and Computation|year=2011|volume=7|issue=11|pages=3816–3828|doi=10.1021/ct200455n|pmid=26598272}}</ref> |
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Several studies have shown that hydrogen bonds play an important role for the stability between subunits in multimeric proteins. For example, a study of sorbitol dehydrogenase displayed an important hydrogen bonding network which stabilizes the tetrameric quaternary structure within the mammalian sorbitol dehydrogenase protein family.<ref>{{cite journal|last=Hellgren|first=M.|author2=Kaiser, C.|author3=de Haij, S.|author4=Norberg, A.|author5=Höög, J. O.|title=A hydrogen-bonding network in mammalian sorbitol dehydrogenase stabilizes the tetrameric state and is essential for the catalytic power|journal=Cellular and Molecular Life Sciences |date=December 2007|volume=64|issue=23|pages=3129–38|pmid=17952367|doi=10.1007/s00018-007-7318-1|s2cid=22090973}}</ref> |
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A protein backbone hydrogen bond incompletely shielded from water attack is a [[dehydron]]. Dehydrons promote the removal of water through proteins or [[ligand|ligand binding]]. The exogenous dehydration enhances the [[electrostatic]] interaction between the [[amide]] and [[carbonyl]] groups by de-shielding their [[charge (physics)|partial charges]]. Furthermore, the dehydration stabilizes the hydrogen bond by destabilizing the [[nonbonded interactions|nonbonded state]] consisting of dehydrated [[charge (physics)|isolated charges]].<ref>{{cite journal|last=Fernández|first=A.|author2=Rogale K.|author3=Scott Ridgway|author4=Scheraga H. A.|title=Inhibitor design by wrapping packing defects in HIV-1 proteins|journal= Proceedings of the National Academy of Sciences|date=June 2004|volume=101|issue=32|pages=11640–5|pmid=15289598|doi=10.1073/pnas.0404641101|pmc=511032|bibcode=2004PNAS..10111640F|doi-access=free}}</ref> |
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[[Wool]], being a protein fibre, is held together by hydrogen bonds, causing wool to recoil when stretched. However, washing at high temperatures can permanently break the hydrogen bonds and a garment may permanently lose its shape. |
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===Cellulose=== |
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Hydrogen bonds are important in the structure of [[cellulose]] and derived polymers in its many different forms in nature, such as [[cotton]] and [[flax]]. |
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[[Image:Kevlar chemical structure.png|thumb|400px|Para-aramid structure]] |
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[[Image:Cellulose strand.svg|thumb|right|260px|A strand of cellulose (conformation I<sub>α</sub>), showing the hydrogen bonds (dashed) within and between cellulose molecules]] |
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===Synthetic polymers=== |
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Many [[polymer]]s are strengthened by hydrogen bonds within and between the chains. Among the [[synthetic polymer]]s, a well characterized example is [[nylon]], where hydrogen bonds occur in the [[repeat unit]] and play a major role in [[crystallization]] of the material. The bonds occur between [[carbonyl]] and [[amine]] groups in the [[amide]] repeat unit. They effectively link adjacent chains, which help reinforce the material. The effect is great in [[aramid]] [[fibre]], where hydrogen bonds stabilize the linear chains laterally. The chain axes are aligned along the fibre axis, making the fibres extremely stiff and strong. |
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The hydrogen-bond networks make both natural and synthetic polymers sensitive to [[humidity]] levels in the atmosphere because water molecules can diffuse into the surface and disrupt the network. Some polymers are more sensitive than others. Thus [[nylon]]s are more sensitive than [[aramid]]s, and [[nylon 6]] more sensitive than [[nylon-11]]. |
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==Symmetric hydrogen bond== |
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A [[symmetric hydrogen bond]] is a special type of hydrogen bond in which the proton is spaced exactly halfway between two identical atoms. The strength of the bond to each of those atoms is equal. It is an example of a [[three-center four-electron bond]]. This type of bond is much stronger than a "normal" hydrogen bond. The effective bond order is 0.5, so its strength is comparable to a covalent bond. It is seen in ice at high pressure, and also in the solid phase of many anhydrous acids such as [[hydrofluoric acid]] and [[formic acid]] at high pressure. It is also seen in the [[bifluoride]] ion [F--H--F]<sup>−</sup>. Due to severe steric constraint, the protonated form of Proton Sponge (1,8-bis(dimethylamino)naphthalene) and its derivatives also have symmetric hydrogen bonds ([N--H--N]<sup>+</sup>),<ref>Khashayar Rajabimoghadam Yousef Darwish Umyeena Bashir Dylan Pitman Sidney Eichelberger Maxime A. Siegler Marcel Swart Isaac Garcia-Bosch Aerobic Oxidation of Alcohols by Copper Complexes Bearing Redox-Active Ligands with Tunable H-Bonding https://doi.org/10.1021/jacs.8b08748</ref> although in the case of protonated Proton Sponge, the assembly is bent.<ref>{{Cite journal|last1=Ozeryanskii|first1=Valery A.|last2=Pozharskii|first2=Alexander F.|last3=Bieńko|first3=Agnieszka J.|last4=Sawka-Dobrowolska|first4=Wanda|last5=Sobczyk|first5=Lucjan|date=2005-03-01|title=[NHN]+ Hydrogen Bonding in Protonated 1,8-Bis(dimethylamino)-2,7-dimethoxynaphthalene. X-ray Diffraction, Infrared, and Theoretical ab Initio and DFT Studies|journal=The Journal of Physical Chemistry A|volume=109|issue=8|pages=1637–1642|doi=10.1021/jp040618l|pmid=16833488|bibcode=2005JPCA..109.1637O|issn=1089-5639}}</ref> |
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==Dihydrogen bond== |
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The hydrogen bond can be compared with the closely related [[dihydrogen bond]], which is also an [[Intermolecular force|intermolecular]] bonding interaction involving hydrogen atoms. These structures have been known for some time, and well characterized by [[X-ray crystallography|crystallography]];<ref name=crab>{{cite journal|title = A New Intermolecular Interaction: Unconventional Hydrogen Bonds with Element-Hydride Bonds as Proton Acceptor|last1 = Crabtree|first1 = Robert H. |author-link1=Robert H. Crabtree|last2 =Siegbahn |first2= Per E. M. |first3= Odile |last3 =Eisenstein |first4 =Arnold L. |last4 =Rheingold |first5 = Thomas F. |last5 =Koetzle|journal = [[Acc. Chem. Res.]]|year = 1996|volume = 29|issue = 7|pages = 348–354|doi = 10.1021/ar950150s|pmid = 19904922}}</ref> however, an understanding of their relationship to the conventional hydrogen bond, [[ionic bond]], and [[covalent bond]] remains unclear. Generally, the hydrogen bond is characterized by a proton acceptor that is a lone pair of electrons in nonmetallic atoms (most notably in the [[nitrogen group|nitrogen]], and [[chalcogen]] groups). In some cases, these proton acceptors may be [[pi-bond]]s or [[metal complexes]]. In the dihydrogen bond, however, a metal hydride serves as a proton acceptor, thus forming a hydrogen-hydrogen interaction. [[Neutron diffraction]] has shown that the [[molecular geometry]] of these complexes is similar to hydrogen bonds, in that the bond length is very adaptable to the metal complex/hydrogen donor system.<ref name=crab/> |
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==Dynamics probed by spectroscopic means== |
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The dynamics of hydrogen bond structures in water can be probed by the [[IR spectrum]] of OH stretching vibration.<ref name="cowan">{{cite journal |author=Cowan ML |title=Ultrafast memory loss and energy redistribution in the hydrogen bond network of liquid H<sub>2</sub>O |journal=Nature |volume=434 |issue=7030 |pages=199–202 |year=2005 |pmid=15758995 |doi=10.1038/nature03383 |author2=Bruner BD |author3=Huse N |display-authors=3 |last4=Dwyer |first4=J. R. |last5=Chugh |first5=B. |last6=Nibbering |first6=E. T. J. |last7=Elsaesser |first7=T. |last8=Miller |first8=R. J. D.|bibcode = 2005Natur.434..199C |s2cid=4396493 }}</ref> In the hydrogen bonding network in protic organic ionic plastic crystals (POIPCs), which are a type of phase change material exhibiting solid-solid phase transitions prior to melting, variable-temperature infrared spectroscopy can reveal the temperature dependence of hydrogen bonds and the dynamics of both the anions and the cations.<ref name="1,2,4-Triazolium perfluorobutanesulfonate as an archetypal pure protic organic ionic plastic crystal electrolyte for all-solid-state fuel cells"/> The sudden weakening of hydrogen bonds during the solid-solid phase transition seems to be coupled with the onset of orientational or rotational disorder of the ions.<ref name="1,2,4-Triazolium perfluorobutanesulfonate as an archetypal pure protic organic ionic plastic crystal electrolyte for all-solid-state fuel cells"> |
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{{cite journal |
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|year = 2015 |
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|title = 1,2,4-Triazolium perfluorobutanesulfonate as an archetypal pure protic organic ionic plastic crystal electrolyte for all-solid-state fuel cells |
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|journal = [[Energy & Environmental Science]] |
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|volume = 8 |
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|issue = 4 |
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|pages = 1276 |
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|doi = 10.1039/C4EE02280G |
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|last1 = Luo |
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|first1 = Jiangshui |
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|last2 = Jensen |
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|first2 = Annemette H. |
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|last3 = Brooks |
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|first3 = Neil R. |
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|last4 = Sniekers |
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|first4 = Jeroen |
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|last5 = Knipper |
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|first5 = Martin |
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|last6 = Aili |
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|first6 = David |
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|last7 = Li |
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|first7 = Qingfeng |
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|last8 = Vanroy |
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|first8 = Bram |
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|last9 = Wübbenhorst |
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|first9 = Michael |
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|last10 = Yan |
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|first10 = Feng |
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|last11 = Van Meervelt |
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|first11 = Luc |
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|last12 = Shao |
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|first12 = Zhigang |
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|last13 = Fang |
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|first13 = Jianhua |
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|last14 = Luo |
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|first14 = Zheng-Hong |
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|last15 = De Vos |
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|first15 = Dirk E. |
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|last16 = Binnemans |
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|first16 = Koen |
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|last17 = Fransaer |
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|first17 = Jan |
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|s2cid = 84176511 |
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|url = https://semanticscholar.org/paper/597630b38bff9080dedb9aa1eba16f9f10092eb4 |
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}}</ref> |
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==Application to drugs== |
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Hydrogen bonding is a key to the design of drugs. According to [[Lipinski's rule of five]] the majority of orally active drugs tend to have between five and ten hydrogen bonds. These interactions exist between [[nitrogen]]–[[hydrogen]] and [[oxygen]]–hydrogen centers.<ref name="Lipinski_2004">{{cite journal | author = Lipinski CA | title = Lead- and drug-like compounds: the rule-of-five revolution | journal = Drug Discovery Today: Technologies |date=December 2004 | volume = 1 | issue = 4 | pages = 337–341 | doi = 10.1016/j.ddtec.2004.11.007 | pmid = 24981612 }}</ref> As with many other [[rules of thumb]], many exceptions exist. |
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==References== |
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{{reflist|35em}} |
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==Further reading== |
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* George A. Jeffrey. ''An Introduction to Hydrogen Bonding (Topics in Physical Chemistry)''. Oxford University Press, USA (March 13, 1997). {{ISBN|0-19-509549-9}} |
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==External links== |
==External links== |
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*[http://www.cheresources.com/jacketed_vessel_design.shtml Jacketed Vessel Design] |
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* [https://web.archive.org/web/20141203035841/http://www.magnet.fsu.edu/education/tutorials/slideshows/bubblewall/index.html The Bubble Wall] (Audio slideshow from the National High Magnetic Field Laboratory explaining cohesion, surface tension and hydrogen bonds) |
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*[https://web.archive.org/web/20070406201444/http://www.ashemorris.com/batch-technologies.aspx Batch Reactor] |
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* [http://scitation.aip.org/content/aip/journal/jcp/129/19/10.1063/1.3006032 isotopic effect on bond dynamics] |
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{{Chemical bonds}} |
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{{Authority control}} |
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[[Category:Chemical reactors]] |
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{{DEFAULTSORT:Hydrogen Bonds}} |
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[[Category:Chemical bonding]] |
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[[Category:Hydrogen physics]] |
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[[Category:Supramolecular chemistry]] |
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[[Category:Intermolecular forces]] |
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Revision as of 09:54, 8 September 2021
The batch reactor is the generic term for a type of vessel widely used in the process industries. Its name is something of a misnomer since vessels of this type are used for a variety of process operations such as solids dissolution, product mixing, chemical reactions, batch distillation, crystallization, liquid/liquid extraction and polymerization. In some cases, they are not referred to as reactors but have a name which reflects the role they perform (such as crystallizer, or bioreactor).
A typical batch reactor consists of a storage tank with an agitator and integral heating/cooling system. These vessels may vary in size from less than 1 litre to more than 15,000 litres. They are usually fabricated in steel, stainless steel, glass-lined steel, glass or exotic alloy. Liquids and solids are usually charged via connections in the top cover of the reactor. Vapors and gases also discharge through connections in the top. Liquids are usually discharged out of the bottom.
The advantages of the batch reactor lie with its versatility. A single vessel can carry out a sequence of different operations without the need to break containment. This is particularly useful when processing toxic or highly potent compounds.
Agitation
The usual agitator arrangement is a centrally mounted driveshaft with an overhead drive unit. Impeller blades are mounted on the shaft. A wide variety of blade designs are used and typically the blades cover about two thirds of the diameter of the reactor. Where viscous products are handled, anchor shaped paddles are often used which have a close clearance between the blade and the vessel walls.
Most batch reactors also use baffles. These are stationary blades which break up flow caused by the rotating agitator. These may be fixed to the vessel cover or mounted on the interior of the side walls.
Despite significant improvements in agitator blade and baffle design, mixing in large batch reactors is ultimately constrained by the amount of energy that can be applied. On large vessels, mixing energies of more than 5 Watts per litre can put an unacceptable burden on the cooling system. High agitator loads can also create shaft stability problems. Where mixing is a critical parameter, the batch reactor is not the ideal solution. Much higher mixing rates can be achieved by using smaller flowing systems with high speed agitators, ultrasonic mixing or static mixers.
Heating and cooling systems
Products within batch reactors usually liberate or absorb heat during processing. Even the action of stirring stored liquids generates heat. In order to hold the reactor contents at the desired temperature, heat has to be added or removed by a cooling jacket or cooling pipe. Heating/cooling coils or external jackets are used for heating and cooling batch reactors. Heat transfer fluid passes through the jacket or coils to add or remove heat.
Within the chemical and pharmaceutical industries, external cooling jackets are generally preferred as they make the vessel easier to clean. The performance of these jackets can be defined by 3 parameters:
- response time to modify the jacket temperature
- uniformity of jacket temperature
- stability of jacket temperature.
It can be argued that heat transfer coefficient is also an important parameter. It has to be recognized however that large batch reactors with external cooling jackets have severe heat transfer constraints by virtue of design. It is difficult to achieve better than 100 Watts/litre even with ideal heat transfer conditions. By contrast, continuous reactors can deliver cooling capacities in excess of 10,000 W/litre. For processes with very high heat loads, there are better solutions than batch reactors.
Fast temperature control response and uniform jacket heating and cooling is particularly important for crystallization processes or operations where the product or process is very temperature sensitive. There are several types of batch reactor cooling jackets:
Single external jacket
The single jacket design consists of an outer jacket which surrounds the vessel. Heat transfer fluid flows around the jacket and is injected at high velocity via nozzles. The temperature in the jacket is regulated to control heating or cooling.
The single jacket is probably the oldest design of external cooling jacket. Despite being a tried and tested solution, it has some limitations. On large vessels, it can take many minutes to adjust the temperature of the fluid in the cooling jacket. This results in sluggish temperature control. The distribution of heat transfer fluid is also far from ideal and the heating or cooling tends to vary between the side walls and bottom dish. Another issue to consider is the inlet temperature of the heat transfer fluid which can oscillate (in response to the temperature control valve) over a wide temperature range to cause hot or cold spots at the jacket inlet points.
Half coil jacket
The half coil jacket is made by welding a half pipe around the outside of the vessel to create a semi circular flow channel. The heat transfer fluid passes through the channel in a plug flow fashion. A large reactor may use several coils to deliver the heat transfer fluid. Like the single jacket, the temperature in the jacket is regulated to control heating or cooling.
The plug flow characteristics of a half coil jacket permits faster displacement of the heat transfer fluid in the jacket (typically less than 60 seconds). This is desirable for good temperature control. It also provides good distribution of heat transfer fluid which avoids the problems of non uniform heating or cooling between the side walls and bottom dish. Like the single jacket design however the inlet heat transfer fluid is also vulnerable to large oscillations (in response to the temperature control valve) in temperature.
Constant flux cooling jacket
The constant flux cooling jacket is a relatively recent development. It is not a single jacket but has a series of 20 or more small jacket elements. The temperature control valve operates by opening and closing these channels as required. By varying the heat transfer area in this way, the process temperature can be regulated without altering the jacket temperature.
The constant flux jacket has very fast temperature control response (typically less than 5 seconds) due to the short length of the flow channels and high velocity of the heat transfer fluid. Like the half coil jacket the heating/cooling flux is uniform. Because the jacket operates at substantially constant temperature however the inlet temperature oscillations seen in other jackets are absent. An unusual feature of this type jacket is that process heat can be measured very sensitively. This allows the user to monitor the rate of reaction for detecting end points, controlling addition rates, controlling crystallization etc.
Applications
Batch reactors are often used in the process industry. Batch reactors also have many laboratory applications, such as small scale production and inducing fermentation for beverage products. They also have many uses in medical production. Batch reactors are generally considered expensive to run, as well as variable product reliability. They are also used for experiments of reaction kinetics, volatiles and thermodynamics. Batch reactors are also highly used in waste water treatment. They are effective in reducing BOD (biological oxygen demand) of influent untreated water.[1][2][3][4][5][6][7][8]
See also
References
- ^ "The Sequencing Batch Reactor as a Powerful Tool for the Study of Slowly Growing Anaerobic Ammonium-oxidizing Microorganisms - Springer." The Sequencing Batch Reactor as a Powerful Tool for the Study of Slowly Growing Anaerobic Ammonium-oxidizing Microorganisms - Springer. N.p., 01 Nov. 1998. Web. 26 Feb. 2014.>
- ^ "Aerobic Granulation in a Sequencing Batch Reactor." Aerobic Granulation in a Sequencing Batch Reactor. N.p., n.d. Web. 26 Feb. 2014.
- ^ "Water Science & Technology 27:5-6 (1993) 241-252 - T. Kuba Et Al. - Biological Phosphorus Removal from Wastewater by Anaerobic-Anoxic Sequencing Batch Reactor." Water Science & Technology 27:5-6 (1993) 241-252 - T. Kuba Et Al. - Biological Phosphorus Removal from Wastewater by Anaerobic-Anoxic Sequencing Batch Reactor. N.p., n.d. Web. 26 Feb. 2014.
- ^ "Aerobic Granular Sludge in a Sequencing Batch Reactor." Aerobic Granular Sludge in a Sequencing Batch Reactor. N.p., n.d. Web. 26 Feb. 2014.
- ^ "Sequencing Batch Reactors - Springer." Sequencing Batch Reactors - Springer. N.p., n.d. Web. 26 Feb. 2014.
- ^ "Sequencing Batch Reactor Technology." Google Books. N.p., n.d. Web. 26 Feb. 2014.
- ^ "Simultaneous Nitrification, Denitrification, and Phosphorus Removal in a Lab-scale Sequencing Batch Reactor." - Zeng. N.p., n.d. Web. 26 Feb. 2014.
- ^ "Nitrification, Denitrification and Biological Phosphorus Removal in Piggery Wastewater Using a Sequencing Batch Reactor." Nitrification, Denitrification and Biological Phosphorus Removal in Piggery Wastewater Using a Sequencing Batch Reactor. N.p., n.d. Web. 26 Feb. 2014.>