In general, the monocyclic cyclopentadiene hydrocarbons are illustrated by the following formula: ##STR1## wherein each R is, independently, hydrogen or a hydrocarbon substituent such as an alkyl group (preferably containing up to about 4 carbon atoms, most preferably methyl), a cycloalkyl group, or an aryl group (preferably phenyl or alkyl substituted phenyl wherein each alkyl group contains up t