Hexamethylenetetramine ( HMTA), also known as 1,3,5,7-tetraazaadamantane, is a heterocycle with diverse applications.
Synthesis, structure, reactivity
Hexamethylenetetramine was discovered by Aleksandr Butlerov in 1859.
[ In this article, Butlerov discovered formaldehyde, which he called "dioxymethylen" (methylene dioxide) page because his empirical formula for it was incorrect (C4H4O4). On pages 249–250, he describes treating formaldehyde with ammonia gas, creating hexamine.]
It is prepared industrially by combining
formaldehyde and
ammonia:
The molecule behaves like an amine base, undergoing protonation and as a ligand.
Applications
The dominant use of hexamethylenetetramine is in the production of solid (powder) or liquid
and phenolic
resin moulding compounds, in which it is added as a hardening component. These products are used as binders, e.g., in brake and clutch linings, abrasives, non-woven textiles, formed parts produced by moulding processes, and fireproof materials.
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Medical uses
The compound is also used medically as a urine antiseptic and antibacterial medication under the name methenamine or hexamine.
As the mandelic acid salt (methenamine mandelate) or the hippuric acid salt (methenamine hippurate),
Methenamine acts as an over-the-counter antiperspirant due to the astringent property of formaldehyde.
Histological stains
Methenamine silver stains are used for staining in histology, including the following types:
-
Grocott's methenamine silver stain, used widely as a screen for fungi microorganisms.
-
Jones' stain, a methenamine silver-Periodic acid-Schiff that stains for basement membrane, availing to view the "spiked" Glomerular basement membrane associated with membranous glomerulonephritis.
Solid fuel
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 of 30.0 joule per kilogram (MJ/kg), does not liquify while burning, and leaves no ashes, although its fumes are toxic.
Standardized 0.149 gram 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.
Food additive
Hexamethylenetetramine 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,[UK Food Standards Agency: ] where it is listed under E number E239, however it is not approved in the USA, Russia, Australia, or New Zealand.[Australia New Zealand Food Standards Code]
Reagent in organic chemistry
Hexamethylenetetramine is a versatile reagent in organic synthesis.
Explosives
Hexamethylenetetramine is the base component to produce RDX and, consequently, C-4[ as well as HMX (a co-product with RDX), hexamine dinitrate, hexamine diperchlorate, HMTD, and R-salt.
]
From October 2023, sale of hexamethylenetetramine in the UK is restricted to licensed persons (as a "regulated precursor" under the terms of the Poisons Act 1972).
Pyrotechnics
Hexamethylenetetramine is also used in pyrotechnics to reduce combustion temperatures and decrease the color intensity of various fireworks.
Historical uses
Hexamethylenetetramine was first introduced into the medical setting in 1895 as a urinary antiseptic.
Hexamethylenetetramine was also used as a method of treatment for soldiers exposed to phosgene in World War I. Subsequent studies have shown that large doses of hexamethylenetetramine provide some protection if taken before phosgene exposure but none if taken afterwards.
Producers
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.[ ] In Australia, Hexamine Tablets for fuel are made by Thales Australia Ltd. In México, Hexamine is produced by Abiya. Many other countries who still produce this include Russia, Saudi Arabia, and China.
Occurrence
In 2020, NASA announced that hexamethylenetetramine had been found in the Murchison, Murray meteorite and Tagish Lake meteorites.
