having 2 4 carbon atoms the term includes without limitation methylidene vinyl vinylidene allyl allylidene propylidene isopropenyl iso propylidene prenyl prenylene 3 methyl 2 butenylene methallyl methallylene allylidene 2 propenylidene crotylene 2 butenylene and the like an alkenyl substituent may be attached to a core molecule via a terminal carbon atom or via a carbon atom within the chain similarly any number of substituent variables may be attached to an alkenyl substituent when allowed by available valences the term u201c alkoxy u201d means an alkyl radical or linking group substituent attached through an oxygen linking atom wherein the radical is of the formula u2014 o alkyl and a linking group is of the formula u2014 o alkyl the term includes without limitation methoxy ethoxy propoxy butoxy and the like an alkoxy substituent may be attached to a core molecule and further substituted where allowed by available valences the term u201c cycloalkyl u201d means a saturated or partially unsaturated monocyclic polycyclic or bridged hydrocarbon ring system radical or linking group a ring of 3 to 20 carbon atoms may be designated by c 3 20 cycloalkyl a ring of 3 to 12 carbon atoms may be designated by c 3 12 cycloalkyl a ring of 3 to 8 carbon atoms may be designated by c 3 8 cycloalkyl and the like a cycloalkyl substituent may be attached to a core molecule and further substituted where allowed by available valences the term cycloalkyl includes without limitation cyclopropyl cyclobutyl cyclopentyl cyclohexyl cyclohexenyl cycloheptyl cyclooctyl indanyl indenyl 1 2 3 4 tetrahydro naphthalenyl 5 6 7 8 tetrahydro naphthalenyl 8 9 dihydro 7h benzocyclohepten 6 yl 6 7 8 9 tetrahydro 5h benzocycloheptenyl 5.