Hexamethylenetetramine, formation structure

Normally the reaction Is useful for the conversion of alkyl halides to primary amines without concomitant formation of secondary amines.29 Treatment of polymer 17 with hexamethylenetetramine in a mixture of ethanol/THF afforded an insoluble resin. Using diazabicyclooctane (DABCO), we demonstrated that the reaction could be limited to attack by a single nitrogen in a multifunctional amine, so we did not anticipate crosslinking via bis-quat salt formation. Hydrolysis of 2 with anhydrous HC1 in ethanol generated free amino groups as evidenced by a positive ninhydrin test, but quantitative hydrolysis could not be achieved and the product remained insoluble. One would have expected a simple bis-quat to hydrolyse and open the crosslinked structure. 

The earlier process for making RDX consisted of reacting hexamine (hexamethylenetetramine) or its dinitrate salt with 98-100 per cent nitric acid. The yields of this method are not good because the formation of RDX is accompanied by the formation of formaldehyde, which is oxidized by the nitric acid. Greatly improved yields (70-80 per cent) can be obtained by means of the Bachman process, which employs hexamine, 98 per cent nitric acid, ammonium nitrate, and acetic anhydride. In the Bachman process a by-product having the structure I is also formed in yields up to 10 per cent. The mechanism of these reactions is not thoroughly understood. 

Tertiary amines [70], some inorganic salts [71], ammonia [70], and l,3,5,7-tetraazatricyclo[3.3.3.P ]decane (hexamethylenetetramine) [72] can catalyze the formation of resoles. The basic pH in the reaction mixture produees a phenolate anion. This anion possesses a higher electron density at the ortho and para positions. Therefore, the electrophilic attack of the carbon end of the methanal occurs more efficiently in these positions. Furthermore, the dehydration of the hydroxymethylol group oecurs slower because the cation of the basic catalyst stabilizes the hydroxymethylated phenols. A typical example for such a stabilized structure is given in Seheme 3. 

Mechanisin of Hezamethylenetetraiome Formation, Hexamethylenete-traunme was probably first prepared in 1859 by Butlerov by reaction of gaseous ammonia and paraformaldehyde (But.lerov s dioxymethylene )-As a r ult of further study, Butleror later identified it as possessing the empirical formula, CeHaKi, and suggested the structural formula shown above. Preparation of hexamethylenetetramine by reaction of formaldehyde and ammonia in aqueous solution was reported by Hofmann in 1869. 

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