An acetal selected from the group consisting of acetals having the structure ##STR51## wherein R11 and R12 are independently an alkyl, aryl, aralkyl, or alkaryl group when n is 1, R11 or R12 is one of the groups when n is 2, or R11 and R12 are not present when n is 3; wherein R13 is an alkyl group, which can contain an ether linkage, or an aralkyl group; R16, R17, and R18 are individually an alkyl