ng 1 to 12 carbon atoms or an arylene radical, R13 is an alkyl radical having from 1 to 12 carbon atoms, preferably from 1 to 4 carbon atoms, or aryl; (4) a cycloaliphatic group including the monocyclic and bicyclic groups such as cyclopropyl, cyclopentyl, cyclohexyl, bicyclo [2.2.1] heptyl, and the like; (5) an aryl, alkyaryl, or aralkyl group which may be substituted by R1 or by substituents (i)