Description
Urotropine (CH₂)₆N₄, also known as methenamine or hexamine, is a polycyclic tertiary amine. Urotropine is a crystalline substance with a closed cage-like structure. It has the form of a white powder that dissolves in water, ethanol, and ether, but is practically insoluble in chloroform and gasoline. Urotropine is prone to the process of hydrolysis, which leads to the release of ammonia and an increase in the pH of the solution, so it has an alkalizing effect. However, the effect is not strong, and its alkalinity is about a million times weaker than triethylamine (Et3N). It is a multifunctional chemical compound used in various fields of industry and medicine. It is classified as a dangerous material with the number UN 1328 according to the ADR regulations.
On an industrial scale, Urotropine is obtained by the reaction of ammonia with formaldehyde in the presence of water. To carry out this reaction, appropriate conditions are required: high temperature (80–100°C) and the presence of a base (e.g. sodium hydroxide). This provides the appropriate pH value and accelerates the condensation of formaldehyde with ammonia. The intermediate products of this reaction are methyldiamine and hexamethylenediamine. Ultimately, urotropine and water are formed. After the reaction is complete, hexamethylenetetramine is isolated by filtration and then crystallization. There are also other methods, although they are less common. An example is the cyclic amine condensation method, in which hexamethylenediamine is used in the reaction with formaldehyde. This method requires smaller reactions, which may be less efficient and more expensive than the direct reaction of ammonia with formaldehyde. There are also studies that indicate the future possibility of using electrochemical methods in organic syntheses or using catalysts to support the condensation of ammonia with formaldehyde. However, these methods are not sufficiently developed at the moment.
Urotropine is a moderately reactive chemical compound. It reacts with acids to form salts by protonation of nitrogen atoms in its structure. It also undergoes pyrolysis, decomposing into various products depending on the conditions. In the presence of oxygen, it burns to form nitrogen oxides, carbon dioxide, and water, and in anaerobic conditions, it leads to the formation of formaldehyde, ammonia, and complex organic products. Urotropine can undergo hydrolysis in an acidic environment, producing formaldehyde and ammonia. In the presence of a nitrating mixture (e.g. nitric and sulfuric acids), urotropine can undergo nitration, forming hexogen (RDX), a powerful explosive. Urotropine also reacts with alkyl halides, leading to the formation of quaternary ammonium salts. In the presence of strong oxidants, urotropine can undergo oxidation, forming compounds containing carbonyl groups.
