1911 Encyclopædia Britannica/Guanidine
GUANIDINE, CN3H5 or HN:C(NH2)2, the amidine of amidocarbonic acid. It occurs in beet juice. It was first prepared in 1861 by A. Strecker, who oxidized guanine with hydrochloric acid and potassium chlorate. It may be obtained synthetically by the action of ammonium iodide on cyanamide, CN·NH2 + NH4I = CN3H5·HI·; by heating ortho-carbonic esters with ammonia to 150° C.; but best by heating ammonium thiocyanate to 180°–190° C., when the thiourea first formed is converted into guanidine thiocyanate, 2CS(NH2)2 = HN:C(NH2)2·HCNS + H2S. It is a colourless crystalline solid, readily soluble in water and alcohol; it deliquesces on exposure to air. It has strong basic properties, absorbs carbon dioxide readily, and forms well-defined crystalline salts. Baryta water hydrolyses it to urea. By direct union with glycocoll acid, it yields glycocyamine, NH2·(HN):C·NH·CH2·CO2H, whilst with methyl glycocoll (sarcosine) it forms creatine, NH2·(NH):C·N(CH3)·CH2·CO2H.
Many derivatives of guanidine were obtained by J. Thiele (Ann.,
1892, 270, p. 1; 1893, 273, p. 133; Ber., 1893, 26, pp. 2598, 2645).
By the action of nitric acid on guanidine in the presence of sulphuric
acid, nitroguanidine, HN:C(NH2)·NH·NO2 (a substance
possessing acid properties) is obtained; from which, by reduction
with zinc dust, amidoguanidine, HN:C(NH2)·NH·NH2, is formed.
This amidoguanidine decomposes on hydrolysis with the formation
of semicarbazide, NH2·CO·NH·NH2, which, in its turn, breaks
down into carbon dioxide, ammonia and hydrazine. Amidoguanidine
is a body of hydrazine type, for it reduces gold and silver salts
and yields a benzylidine derivative. On oxidation with potassium
permanganate, it gives azodicarbondiamidine nitrate,
NH2·(HN):C·N:N·C:(NH)·NH2·2HNO3, which, when reduced by sulphuretted
hydrogen, is converted into the corresponding hydrazodicarbondiamidine,
NH2·(HN):C·NH·NH·C:(NH)·NH2. By the action of
nitrous acid on a nitric acid solution of amidoguanidine, diazoguanidine
nitrate, NH2·(HN):C·NH·N2·NO3, is obtained. This diazo
compound is decomposed by caustic alkalis with the formation
of cyanamide and hydrazoic acid, CH4N5·NO3 = N3H + CN·NH2 + HNO3,
whilst acetates and carbonates convert it into amidotetrazotic
acid,
Amidotetrazotic acid yields addition
compounds with amines, and by the further action of nitrous acid
yields a very explosive derivative, diazotetrazol, CN6. By fusing
guanidine with urea, dicyandiamidine H2N·(HN):C·NH·CO·NH2, is
formed.