Ureide(redirected from ureides)
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(also known as ureid), any of the derivatives of urea [CO(NH2)2] resulting from the substitution of acyl (RCO) radicals for hydrogen atoms in the NH2 groups. Ureides are crystalline, high-melting compounds; the melting point of acetylurea (CH3CONHCONH2) is 218°C, while that of diacetylurea (CH3CONH)2CO is 153°C. Cyclic ureides are obtained from the reaction of urea with dibasic acids; for example, barbituric acid is obtained by reacting urea with malonic acid or malonic ester. The ureides of brome-substituted acids (bromisoval, carbromal) and cyclic ureides of the barbiturate type are used as sedatives.