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Online Encyclopedia
Originally appearing in Volume V01, Page 855 of the 1911 Encyclopedia Britannica.
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AMIDINES, in organic chemistry, the name given to compounds of general formula R•C: (NH). NH2, which maybe considered as derived from the acid-amides by replacement 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 (O. Wallach, A. Bernthsen); 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 (O. Wallach, Ber., 1882, 15, p. 208); and by the action of ammonia or amines on imino-ethers (A. Pinner, Ber., 1883, 16, p. 1647; 1884, 17,p. 179). They are monacid bases, which are not very stable; they readily take up the elements of water (when boiled with acids or alkalies) , yielding amides and ammonia. On dry distillation they yield nitriles and ammonia. When warmed with sulphuretted hydrogen they yield thiamides, RC : (NH) •NHR+H2S = R C(NH2)(SH)NHR=R•CSNH2+NH2•R or RCS .NHR+ NH3. With 0-ketonic esters, HO(CH3)C : CH. CO2R, they yield oxypyrimidines (A. Pinner, Ber., 1890, 23, p. 3820). Formamidine, HC: (NH)NH2, is only known in the form of its salts, the hydrochloride being obtained by the action of ammonia on the hydrochloride of formimido-ethyl ether (A. Pinner, Ber., 1883, 16, p. 3S7). Acetamidine, CH3C : (NH)•NH2, is alkaline in reaction, and readily splits up into acetic acid and ammonia when warmed with acids. Its hydrochloride melts at 163° C., and crystallizes from alcohol in colourless deliquescent prisms. Acetic anhydride converts the base into an acetamino-dimethyl pyrimidine, acetic acid and acetamide being also formed. Benzamidine, C6H5•C: (NH)NH2, forms colourless crystals which melt at 75—800 C. When warmed it breaks down into ammonia and cyanphenine (s-triphenyl triazine). It condenses with acetic anhydride to form a methyldiphenyl triazine, acetamide being also formed; with acetyl-acetone to form dimethylphenyl pyrimidine (A. Pinner, Ber., 1893, 26, p. 2125); and with trimethylene bromide to form a phenyl tetrahydropyrimidine (Pinner). H. v. Pechmann (Ber., 1895, 28, p. 2362) has shown that amidines of the type R•C: (NY)•NHZ sometimes react as if they possessed the constitution R•C (NZ). NHY; but this only appears to occur when Y and Z are groups which function in the same way. If Y and Z are groups which behave very differently, then there is apparently no tautomerism and a definite formula can be given to the compound. The formulae of the ringed compounds mentioned above are here shown: N —C—(CH3) / > CH =C—(OH) Oxypyrimidine. N —C/C6H6 \N NC\CH3 Methyldiphenyl triazine. Phenyl tetrahydropyrimidine.
End of Article: AMIDINES

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