(a) an aldehyde (???CO???H); (b) a ketone (???CO???R) where R may be for example a straight chain alkyl group having for example 1 to about 20 carbon atoms, particularly 1 to about 12 carbon atoms, such as methyl, ethyl, pentyl, decyl and dodecyl; a branched alkyl group having for example 3 to about 40 carbon atoms, particularly 3 to about 30 carbon atoms such as isopropyl, isopentyl and 2-propyl-