Jump to content

Arsenous acid: Difference between revisions

Browse history interactively
Page 1
Page 2
← Previous edit
Content deleted Content added
VisualWikitext
CheMoBot (talk | contribs)
Bots
141,565 edits
Updating {{chembox}} (no changed fields - added verified revid - updated 'UNII_Ref', 'ChEMBL_Ref') per Chem/Drugbox validation (report errors or bugs)
GreenC bot (talk | contribs)
Bots
2,244,126 edits
Move 1 url. Wayback Medic 2.5
 
(54 intermediate revisions by 43 users not shown)
Line 1: Line 1:
{{Chembox
{{Chembox
| verifiedrevid = 455187134
| verifiedrevid = 455188109
| Name = Arsenous acid
| Name = Arsenous acid
| ImageFile = Arsenous-acid-2D.png
| ImageFile = Arsenous-acid-2D.svg
| ImageSize = 200px
| ImageSize = 170px
| ImageAlt =
| ImageAlt = Structural formula
| ImageCaption =
| ImageCaption =
| ImageFile1 = Arsenous-acid-3D-vdW.png
| ImageFile1 = Arsenous-acid-3D-balls.png
| ImageSize1 = 200px
| ImageSize1 = 170px
| ImageAlt1 =
| ImageAlt1 = Ball-and-stick model
| ImageCaption1 =
| ImageCaption1 =
| IUPACName = Arsorous acid
| IUPACName = Arsorous acid
| PIN =
| PIN =
| SystematicName =
| SystematicName =
| OtherNames = Arsenious acid
| OtherNames = Arsenious acid<br>Arsenic oxide
| Section1 = {{Chembox Identifiers
|Section1={{Chembox Identifiers
| Abbreviations =
| Abbreviations =
| CASNo = 13464-58-9
| CASNo = 13464-58-9
| CASNo_Comment =
| CASNo_Comment =
| CASNo_Ref =
| CASNo_Ref = {{cascite|correct|??}}
| UNII_Ref = {{fdacite|correct|FDA}}
| CASNos =
| PubChem = 545
| UNII = 935XD1L5K2
| PubChem = 545
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 530
| ChemSpiderID = 530
| SMILES = O[As](O)O
| SMILES = O[As](O)O
| InChI = 1/AsH3O3/c2-1(3)4/h2-4H
| InChI = 1/AsH3O3/c2-1(3)4/h2-4H
| InChIKey = GCPXMJHSNVMWNM-UHFFFAOYAA
| InChIKey = GCPXMJHSNVMWNM-UHFFFAOYAA
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/AsH3O3/c2-1(3)4/h2-4H
| StdInChI = 1S/AsH3O3/c2-1(3)4/h2-4H
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = GCPXMJHSNVMWNM-UHFFFAOYSA-N
| StdInChIKey = GCPXMJHSNVMWNM-UHFFFAOYSA-N
| EINECS =
| EINECS =
| EC-number =
| EC_number =
| EINECSCASNO =
| UNNumber =
⚫
| DrugBank_Ref = {{drugbankcite|correct|drugbank}}
| UNNumber =
⚫
| DrugBank_Ref = {{drugbankcite|correct|drugbank}}
| DrugBank = DB04456
| DrugBank = DB04456
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG =
| KEGG =
| MeSHName =
| MeSHName =
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 49900
| ChEBI = 49900
| RTECS =
| RTECS =
| ATCvet =
| Beilstein =
⚫
| Gmelin =
| ATCCode_prefix =
⚫
| 3DMet =
| ATCCode_suffix =
| ATC_Supplemental =
| Beilstein =
⚫
| Gmelin =
⚫
| 3DMet =
}}
}}
| Section2 = {{Chembox Properties
|Section2={{Chembox Properties
| Formula = H<sub>3</sub>AsO<sub>3</sub>
| Formula = H<sub>3</sub>AsO<sub>3</sub>
| MolarMass = 125.94 g/mol
| MolarMass = 125.94 g/mol
| Appearance = Only exists in aqueous solutions
| Appearance = Only exists in aqueous solutions
| Density =
| Density =
| MeltingPt =
| MeltingPt =
| Melting_notes =
| MeltingPt_notes =
| BoilingPt =
| BoilingPt =
| Boiling_notes =
| BoilingPt_notes =
| LogP =
| LogP =
| VaporPressure =
| VaporPressure =
| HenryConstant =
| HenryConstant =
| AtmosphericOHRateConstant =
| AtmosphericOHRateConstant =
| ConjugateBase = [[Ortho-arsenite|Arsenite]]
⚫
| pKa =
| pKb =
| pKa =
⚫
| pKb =
| MagSus = -51.2·10<sup>−6</sup> cm<sup>3</sup>/mol
}}
}}
| Section3 = {{Chembox Structure
|Section3={{Chembox Structure
| CrystalStruct =
| CrystalStruct =
| Coordination =
| Coordination =
| MolShape =
| MolShape =
}}
}}
| Section4 = {{Chembox Thermochemistry
|Section4={{Chembox Thermochemistry
| Solubility =
| SolubleOther =
| Solvent =
}}
}}
| Section7 = {{Chembox Hazards
|Section7={{Chembox Hazards
| ExternalMSDS =
| ExternalSDS =
⚫
| MainHazards = Toxic, corrosive
| EUClass =
| EUIndex =
| NFPA-H =
⚫
| NFPA-F =
⚫
| MainHazards = Toxic, corrosive
| NFPA-H =
| NFPA-R =
| NFPA-F =
| NFPA-S =
| NFPA-R =
| LD50 =
| IDLH = Ca [5 mg/m<sup>3</sup> (as As)]<ref name=PGCH>{{PGCH|0038}}</ref>
⚫
| NFPA-O =
| REL = Ca C 0.002 mg/m<sup>3</sup> [15-minute]<ref name=PGCH/>
| RPhrases =
| PEL = [1910.1018] TWA 0.010 mg/m<sup>3</sup><ref name=PGCH/>
| SPhrases =
| RSPhrases =
| LD50 =
}}
}}
| Section8 = {{Chembox Related
|Section8={{Chembox Related
| OtherAnions =
| OtherAnions =
| OtherCations =
| OtherCations =
| OtherFunctn =
| OtherFunction =
| Function =
| OtherFunction_label =
| OtherCpds = [[Arsenic acid]] }}
| OtherCompounds = [[Arsenic acid]] }}
}}
}}


'''Arsenous acid''', also known as '''arsenious acid''', is the [[inorganic compound]] with the formula H<sub>3</sub>AsO<sub>3</sub>. It is known to occur in aqueous [[solution]]s, but it has not been isolated as a pure material, although this fact does not detract from the significance of As(OH)<sub>3</sub>.<ref>{{cite book
'''Arsenous acid''' (or '''arsenious acid''') is the [[inorganic compound]] with the formula H<sub>3</sub>AsO<sub>3</sub>. It is known to occur in [[aqueous solution]]s, but it has not been isolated as a pure material, although this fact does not detract from the significance of As(OH)<sub>3</sub>.<ref>{{cite encyclopedia | editor = King, R. B. | author = Munoz-Hernandez, M.-A. | title = Arsenic: Inorganic Chemistry | year = 1994 | encyclopedia = Encyclopedia of Inorganic Chemistry | publisher = John Wiley & Sons | location = Chichester }}</ref>
| first = R. Bruce "(ed.)"
| last = King
| year = 1994
| title = [[Encyclopedia of Inorganic Chemistry]]
| publisher = John Wiley & Sons
| location = Chichester
}}</ref>


==Properties==
==Properties==
[[File:H3PO3new.svg|thumb|left|146 px|[[Phosphorous acid]] exists in as the dihydroxy tautomer in contrast to arsenous acid.]]
As(OH)<sub>3</sub> is a pyramidal molecule consisting of three [[hydroxide|hydroxyl]] groups bonded to arsenic. The <sup>1</sup>H [[NMR]] spectrum of arsenous acid solutions consists of a single signal consistent with the molecule's high symmetry.{{Citation needed|date=October 2010}} In contrast, the nominally related [[phosphorus]] species H<sub>3</sub>PO<sub>3</sub> mainly adopts the structure HPO(OH)<sub>2</sub>; P(OH)<sub>3</sub> is a very minor equilibrium component of such solutions. The differing behaviors of the As and P compounds reflect a trend whereby high oxidation states are more stable for lighter members of main group elements than their heavier congeners.<ref>{{cite book
As(OH)<sub>3</sub> is a pyramidal molecule consisting of three [[hydroxide|hydroxyl]] groups bonded to arsenic. The <sup>1</sup>H [[NMR]] spectrum of arsenous acid solutions consists of a single signal consistent with the molecule's high symmetry.<ref>{{cite journal | title = A pH-Metric, UV, NMR, and X-ray Crystallographic Study on Arsenous Acid Reacting with Dithioerythritol | author1 = Kolozsi, A. | author2 = Lakatos, A. | author3 = Galbács, G. | author4 = Madsen, A. Ø. | author5 = Larsen, E. | author6 = Gyurcsik, B. | journal = Inorganic Chemistry | year = 2008 | volume = 47 | issue = 9 | pages = 3832–3840 | url = http://www.staff.u-szeged.hu/~galbx/Arsenous%20acid%20study%20%28Inorg%20Chem%202008%29.pdf | doi = 10.1021/ic7024439 | pmid = 18380458 | access-date = 2011-12-18 | archive-url = https://web.archive.org/web/20120425201802/http://www.staff.u-szeged.hu/~galbx/Arsenous%20acid%20study%20(Inorg%20Chem%202008).pdf | archive-date = 2012-04-25 | url-status = dead }}</ref> In contrast, the nominally related [[phosphorous acid]] H<sub>3</sub>PO<sub>3</sub> adopts the structure HPO(OH)<sub>2</sub>. The structural analogue of arsenous acid (P(OH)<sub>3</sub>) is a very minor equilibrium component of such solutions. The differing behaviors of the As and P compounds reflect a trend whereby high oxidation states are more stable for lighter members of main group elements than their heavier congeners.<ref name = "Greenwood">{{Greenwood&Earnshaw}}</ref>
| first = N.N.

| last = Greenwood
One tautomer of arsenous acid is HAsO(OH)<sub>2</sub>, which is called [[arsonic acid]]. It has not been isolated or well-characterized.
| coauthors= A. Earnshaw

| year = 1997
==Synthesis==
| title = Chemistry of the Elements
The preparation of As(OH)<sub>3</sub> involves a slow [[hydrolysis]] of [[arsenic trioxide]] in water. Addition of [[base (chemistry)|base]] converts arsenous acid to the [[arsenite|arsenite ions]] [AsO(OH)<sub>2</sub>]<sup>−</sup>, [AsO<sub>2</sub>(OH)]<sup>2−</sup>, and [AsO<sub>3</sub>]<sup>3−</sup>.
| publisher = Butterworth-Heinemann
| location = Oxford
}}</ref>


==Reactions==
==Reactions==
The preparation of As(OH)<sub>3</sub> involves a slow [[hydrolysis]] of [[arsenic trioxide]] in water. Addition of [[base (chemistry)|base]] converts arsenous acid to the [[arsenite|arsenite ions]] [AsO(OH)<sub>2</sub>]<sup>-</sup>, [AsO<sub>2</sub>(OH)]<sup>2-</sup>, and [AsO<sub>3</sub>]<sup>3-</sup>. The first pK<sub>a</sub> is 9.2. Reactions attributed to aqueous [[arsenic trioxide]] are due to arsenous acid and its conjugate bases.
With its first p''K''<sub>a</sub> being 9.2, As(OH)<sub>3</sub> is a weak acid.<ref name = "Greenwood"/> Reactions attributed to aqueous [[arsenic trioxide]] are due to arsenous acid and its conjugate bases.

Like arsenic trioxide, arsenous acid is sometimes [[amphoteric]]. For example, it reacts with hydrochloric, hydrobromic, and hydroiodic acids to produce arsenic trichloride, tribromide, and triiodide.

:As(OH)<sub>3</sub> + 3 HCl ⇌ AsCl<sub>3</sub> + 3 H<sub>2</sub>O
:As(OH)<sub>3</sub> + 3 HBr ⇌ AsBr<sub>3</sub> + 3 H<sub>2</sub>O
:As(OH)<sub>3</sub> + 3 HI ⇌ AsI<sub>3</sub> + 3 H<sub>2</sub>O

Reaction of arsenous acid with [[methyl iodide]] gives [[methylarsonic acid]]. This historically significant conversion is the [[Meyer reaction]]:<ref>{{cite journal|title=Ueber einige anomale Reaktionen|author=G. Meyer|journal=Berichte der Deutschen Chemischen Gesellschaft|pages=1439–1443|volume=13|year=1883|doi=10.1002/cber.188301601316}}</ref>
:As(OH)<sub>3</sub> + CH<sub>3</sub>I + NaOH ⇌ CH<sub>3</sub>AsO(OH)<sub>2</sub> + NaI + H<sub>2</sub>O
Alkylation occurs at arsenic, and the [[oxidation state]] of arsenic increases from +3 to +5.


==Toxicology==
==Toxicology==
Arsenic containing compounds are highly toxic and [[carcinogenic]]. The [[anhydride]] form of arsenous acid, [[arsenic trioxide]], is used as a [[herbicide]], [[pesticide]], and [[rodenticide]].
Arsenic-containing compounds are highly toxic and [[carcinogenic]]. The [[anhydride]] form of arsenous acid, [[arsenic trioxide]], is used as a [[herbicide]], [[pesticide]], and [[rodenticide]].


==References==
==References==
{{reflist}}
<references/>

* {{cite web | title=Arsenic trioxide| work=| url=http://www.pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC33821| accessdate=January 29, 2006 }}


==External links==
==External links==
* [http://www.atsdr.cdc.gov/HEC/CSEM/arsenic Case Studies in Environmental Medicine - Arsenic Toxicity]
* [https://www.atsdr.cdc.gov/csem/csem.html Case Studies in Environmental Medicine - Arsenic Toxicity]


{{Hydrogen compounds}}
{{Hydrogen compounds}}


{{DEFAULTSORT:Arsenous Acid}}
{{DEFAULTSORT:Arsenous Acid}}
[[Category:Acids]]
[[Category:Oxoacids]]
[[Category:Arsenic compounds]]
[[Category:Arsenites]]
[[Category:Hydrogen compounds]]
[[Category:Arsenic(III) compounds]]

[[ar:حمض الزرنيخوز]]
[[zh-min-nan:A-phi-sng]]
[[de:Arsenige Säure]]
[[es:Ácido arsenioso]]
[[fr:Acide orthoarsénieux]]
[[hr:Arsenitna kiselina]]
[[ja:亜ヒ酸]]
[[pl:Kwas arsenowy(III)]]
[[fi:Arseenihapoke]]
[[zh:亚砷酸]]
Retrieved from "https://en.wikipedia.org/wiki/Special:ComparePages"