products that were insoluble in all common solvents and no molecular weights have been determined.The yields of I, II and III are 40, 20 and 40 % , respectively, based on the thiophene reacted, when two moles of thiophene was treated with one mole of formaldehyde and three moles of ammonium chloride. The excess reactants were recoverable. Attempts to improve the yields of I and II are being made.Hexamethylenetetramine was found to react with thiophene in the presence of concentrated hydrochloric acid to give 7% of I, 25% of II and 68% of III on a weight per cent. basis.Superficially, at least, this reaction appears to be similar to the Mannich reaction with ketones. It differs in that free amine bases and formaldehyde appear not to react and that primary and secondary amine hydrochlorides do not react as rapidly as ammonium chloride.A preliminary study of the reaction with thiophene derivatives indicates wide applicability. Full details of the reaction with such derivatives as 2- and 3-methylthiophene, 2-chlorothiophene, and 2-t-butylthiophene will be reported in a later communication.