AMIDINES, the name given to compounds of general formula R•C : (NH) which may be considered as derived from the acid-amides, R•CO•NH2 (see AMIDES) by replace ment of oxygen by the divalent imino (=NH) group. They may be prepared by the action of ammonia or amines on imide chorides or on thiamides; by the action of ammonium chloride or hydrochlorides of amines on nitriles; by condensing amines and amides in presence of phosphorus trichloride ; by the action of hydrochloric acid on acid-amides; and by the action of ammonia or amines on imino-ethers. They are colourless crystalline bases, which are unstable ; they readily take up the elements of water (when boiled with acids or alkalis), yielding amides and ammonia. On dry distillation they yield nitriles and ammonia. With 0-ketonic esters, HO (CH3) C : CH•CO2R, they yield oxypyri midines.
Formamidine, HC : is only known in the form of its salts, the crystalline hydrochloride being obtained by the action of ammonia on the hydrochloride of f ormimido-ethyl ether.
Acetamidine, : (NH) is alkaline in reaction, and readily splits up into acetic acid and ammonia when warmed with acids. Its hydrochloride crystallizes from alcohol in colour less deliquescent prisms.
Benzamidine, forms colourless crystals which melt at 75-80°C.