Formation, heats Hexamethylenetetramine

The reaction mixture is dehydrated at temperatures as high as 160°C (higher temperatures can be tolerated than with resoles). The prepolymer is cooled, crushed, blended with 5-15% hexamethylenetetramine, (CH2)6N4, and sold to the fabricator. Hexamethylenetetramine, referred to as hexa, is the product of the reaction of 6 mol of formaldehyde and 4 mol of ammonia. Curring occurs rapidly on heating with the formation of both methylene and ben-zylamine crosslinking bridges between benzene rings. The crosslinked network is pictured as... 

Naphthaldehyde has been prepared from /3-chloro- or bromomethylnaphthalene by use of hexamethylenetetramine, or by oxidation with lead nitrate from /3-naphthoic acid by distillation with calcium formate, or by reduction with sodium amalgam in boric acid solution from /3-naphthylcarbinol by oxidation with chromic acid and from (3-naphthylglyoxylic acid by saponification, heating with aniline, and hydrolysis of the anil." It has been prepared from j8-naphthylmagnesium bromide and ethoxymethyleneaniline or orthoformic ester, ... 

The reaction of curing is not clear. It is known that under controlled conditions phenol and hexamethylenetetramine form a crystalline salt of the stiochiometric composition C6H12N4 SCeHsOH [30] which, when heated, evolves ammonia with the formation of an insoluble, infusible polymer [31]. In the presence of water, hexamethylenetetramine hydrolyzes with the formation of two moles of dimethylolamine DMA, one mole of formaldehyde and two moles of ammonia. Water is ubiquitious in novolacs and therefore under basic reaction conditions in the presence of tert and sec amines and also ammonia as shown in the chart, methylene bridges are formed by entering formaldehyde into the reaction. With increasing amounts of hexamethylenetetramine, the benzylamine type bridges become predominant. 

In 1897 Del pine reported that the heat of formation of formaldehyde was 25.4 kcal. This figure, determined indirectly from the heat of combustion of hexamethylenetetramine and the heat of reaction of formaldehyde and ammonia, is naturally less accurate than the later measurements. Recalculated on ihe basis of Rossini s values, this figure becomes 24.7 kcals. 

On heating in aqueous or dilute alcoholic solutions, the hexamethylenetetramine addition compounds of alfcyl or aralkyl halides undergo further re -action with formation of carbonyl compounds. This is the basis of the Sonunelet synthesis , by hich halides are converted to aldehy des and... 

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