By using urea, guanidine, thiourea and related compounds instead of amidines, one obtains the uracils.
Uracil and its homologues may be obtained in many cases from the hydrouracils by the action of bromine, and subsequent elimination of the elements of hydrobromic acid; or by the condensation of aceto-acetic ester and related substances with urea, thiourea, guanidine, &c. Uracil, C4H402N2, crystallizes in colourless needles, is soluble in hot water and melts with decomposition at 335° C. Hydrouracil, C4H602N2, is obtained by the action of bromine and caustic alkalis on succinamide (H.
Nencki has shown that alloxan combines with thiourea in alcoholic solution, in the presence of sulphur dioxide to form pseudothiouric acid, C 5 H 6 N 4 S0 3.
Thiourea, or sulphocarbamide, CS(NH 2) 2, is formed by prolonged fusion of ammonium thiocyanate (E.
The alkyl derivatives of thiourea are obtained by the action of ammonia and of primary and secondary amines on the mustard oils (A.
Thiourea and many of its unsymmetrical derivatives have marked physiological action; thiourea causes a slowing of the pulse and respiration, cardiac failure, and death in convulsions; phenyl-, ethyland acetyl-thiourea are actively toxic. The most important derivative pharmacologically is allyl-thiourea, also known as thiosinamine or rhodallin, NH2 CS NH CH2 CH:CH2.