Hexamethylenetetramine

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Hexamethylenetetramine
Hexamine.svg Hexamine-3D-balls.png
Identifiers
CAS number 100-97-0 YesY
PubChem 4101
ChemSpider 3959 YesY
UNII J50OIX95QV YesY
EC number 202-905-8
KEGG D00393 YesY
MeSH Methenamine
ChEBI CHEBI:6824 YesY
ChEMBL CHEMBL1201270 N
ATC code J01XX05
Jmol-3D images Image 1
Properties
Molecular formula C6H12N4
Molar mass 140.186 g/mol
Appearance White crystalline solid
Density 1.33 g/cm³ (at 20 °C)
Melting point 280 °C (sublimes)
Solubility in water 85.3 g/100 mL
Acidity (pKa) 4.89[1]
Hazards
Main hazards Highly flammable, harmful
Flash point 250 °C (482 °F; 523 K)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Hexamethylenetetramine or methenamine is a heterocyclic organic compound with the formula (CH2)6N4. This white crystalline compound is highly soluble in water and polar organic solvents. It has a cage-like structure similar to adamantane. It is useful in the synthesis of other chemical compounds, e.g. plastics, pharmaceuticals, rubber additives. It sublimes in vacuum at 280 °C.

Synthesis, structure, reactivity[edit]

The compound was discovered by Aleksandr Butlerov in 1859.[2][3][4]

Hexamethylenetetramine is prepared industrially by combining formaldehyde and ammonia.[5] The reaction can be conducted in gas phase and in solution.

The molecule has a symmetric tetrahedral cage-like structure, similar to adamantane, whose four "corners" are nitrogen atoms and "edges" are methylene bridges. Although the molecular shape defines a cage, no void space is available at the interior for binding other atoms or molecules, unlike crown ethers or larger cryptand structures.

The molecule behaves like an amine base, undergoing protonation and N-alkylation.

Applications[edit]

The dominant use of hexamethylenetetramine is in the production of powdery or liquid preparations of phenolic resins and phenolic resin moulding compounds, where it is added as a hardening component. These products are used as binders, e.g. in brake and clutch linings, abrasive products, non-woven textiles, formed parts produced by moulding processes, and fireproof materials.[5]

Medical uses[edit]

As the mandelic acid salt (generic methenamine mandelate, USP[6]) it is used for the treatment of urinary tract infection. It decomposes at an acidic pH to form formaldehyde and ammonia, and the formaldehyde is bactericidal; the mandelic acid adds to this effect. Urinary acidity is typically ensured by co-administering vitamin C (ascorbic acid) or ammonium chloride. Its use had temporarily been reduced in the late 1990s, due to adverse effects, particularly chemically-induced hemorrhagic cystitis in overdose,[7] but its use has now been re-approved because of the prevalence of antibiotic resistance to more commonly used drugs. This drug is particularly suitable for long-term prophylactic treatment of urinary tract infection, because bacteria do not develop resistance to formaldehyde. It should not be used in the presence of renal insufficiency.[medical citation needed]

Histological stains[edit]

Methenamine silver stains are used for staining in histology, including the following types:

Solid fuel[edit]

Together with 1,3,5-trioxane, hexamethylenetetramine is a component of hexamine fuel tablets used by campers, hobbyists, the military and relief organizations for heating camping food or military rations. It burns smokelessly, has a high energy density (30.0 MJ/kg), does not liquify while burning, and leaves no ashes.

Standardized 0.149 g tablets of methenamine (hexamine) are used by fire-protection laboratories as a clean and reproducible fire source to test the flammability of carpets and rugs.[8]

Food additive[edit]

Hexamethylene tetramine or hexamine is also used as a food additive as a preservative (INS number 239). It is approved for usage for this purpose in the EU,[9] where it is listed under E number E239, however it is not approved in the USA, Russia, Australia, or New Zealand.[10]

Reagent in organic chemistry[edit]

Hexamethylenetetramine is a versatile reagent in organic synthesis.[11] It is used in the Duff reaction (formylation of arenes),[12] the Sommelet reaction (converting benzyl halides to aldehydes),[13] and in the Delepine reaction (synthesis of amines from alkyl halides).[14]

Explosives[edit]

Hexamethylenetetramine is the base component to produce RDX and, consequently, C-4[5] as well as Hexogen, Oktogen, hexamine dinitrate and HMTD.

Producers[edit]

Since 1990 the number of European producers has been declining. The French SNPE factory closed in 1990; in 1993, the production of hexamethylenetetramine in Leuna, Germany ceased; in 1996, the Italian facility of Agrolinz closed down; in 2001, the UK producer Borden closed; in 2006, production at Chemko, Slovak Republic, was closed. Remaining producers include INEOS in Germany, Caldic in the Netherlands, and Hexion in Italy. In the US, Eli Lilly and Company stopped producing methenamine tablets in 2002.[8] In Australia, Hexamine Tablets for fuel are made by Thales Australia Ltd. In México, Hexamine is produced by Abiya.

References[edit]

  1. ^ Cooney, Aidan P.; Crampton, Michael R.; Golding, Peter (1986). "The acid-base behaviour of hexamine and its N-acetyl derivatives". Journal of the Chemical Society, Perkin Transactions 2 (6): 835. doi:10.1039/P29860000835. 
  2. ^ A. Butlerow (1859) "Ueber einige Derivate des Jodmethylens" (On some derivatives of methylene iodide), Annalen der Chemie und Pharmacie, vol. 111, pages 242–252. In this paper, Butlerov discovered formaldehyde, which he called "Dioxymethylen" (methylene dioxide) [page 247] because his empirical formula for it was incorrect (C4H4O4). On pages 249–250, he describes treating formaldehyde with ammonia gas, creating hexamine.
  3. ^ See also: A. Butlerow (1860) "Ueber ein neues Methylenderivat" (On a new methylene derivative), Annalen der Chemie und Pharmacie, vol. 115, no. 3, pages 322–327.
  4. ^ http://library.istu.edu/hoe/books/ruschem.pdf
  5. ^ a b c Karsten Eller, Erhard Henkes, Roland Rossbacher, Hartmut Höke "Amines, Aliphatic" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH Verlag, Weinheim. doi:10.1002/14356007.a02_001
  6. ^ "Methenamine mandelate, USP". Edenbridge Pharmaceuticals. 
  7. ^ Ross Jr, RR; Conway, GF (1970). "Hemorrhagic cystitis following accidental overdose of methenamine mandelate". American journal of diseases of children (1960) 119 (1): 86–7. PMID 5410299. 
  8. ^ a b Alan H. Schoen (2004), Re: Equialence of methenamine Tablets Standard for Flammability of Carpets and Rugs. U.S. Consumer product Safety Commission, Washington, DC, July 29, 2004. Many other countries who still produce this include Russia, Saudi Arabia, China and Australia.
  9. ^ UK Food Standards Agency: "Current EU approved additives and their E Numbers". Retrieved 2011-10-27. 
  10. ^ Australia New Zealand Food Standards Code"Standard 1.2.4 - Labelling of ingredients". Retrieved 2011-10-27. 
  11. ^ Nikola Blažzević, D. Kolbah, Branka Belin, Vitomir Šunjić, Franjo Kajfež Synthesis "Hexamethylenetetramine, A Versatile Reagent in Organic Synthesis" 1979; 1979(3): 161-176. doi:10.1055/s-1979-28602
  12. ^ A. T. Bottini, Vasu Dev, and Jane Klinck (1963), Syringic Aldehyde, Org. Synth. ; Coll. Vol. 4: 866 
  13. ^ Kenneth B. Wiberg (1963), 2-Thiophenaldehyde, Org. Synth. ; Coll. Vol. 3: 811 
  14. ^ A. T. Bottini, Vasu Dev, and Jane Klinck (1963), 2-Bromoallylamine, Org. Synth. ; Coll. Vol. 5: 121