up consisting of hydrogen, an alkyl radical containing from 1 to 8 carbon atoms, an aromatic radical, an alkenyl radical containing from 2 to 8 carbon atoms, and an aralkyl radical, and R2 is a member selected from the group consisting of an alkyl radical containing from 1 to 8 carbon atoms, an alkenyl radical containing from 2 to 8 carbon atoms, an aromatic radical, an aralkyl radical, an alkaryl