Struktur und Wirkung von morpholinoalkylsubstituierten Barbitursäuren. 2. Mitt.: Einfluß der Substituenten auf die Ionisationskonstanten und die pharmakologische Wirkung

Structure and Action of Morpholinoalkyl-Barbiturates The influence of the sustituents on the pKa_base and pKa_acid values in several morpholinoalkyl-barbiturates is discussed. It was shown that: 1. The place of the morpholine residue accounting for the possibility of keto-enol and lactam-lactim tautomerism is of the greatest importance for the pKa_base values. 2. The distance of the morpholine residue from the barbituric ring leads to an insignificant increase of the basic character of the compound. 3. An influence of both the pKa_base and pKa_acid is exercised by the substitution of the ethyl by the phenyl-group at C-5 of the barbituric ring. This substitution leads to a decrease of their values. 4. The pharmacological action is connected with the insignificant degree of their ionisation at blood plasma pH.