{HEAD ~ X} is hydrogen, lower alkyl of 1 6 carbon atoms, cycloalkyl of 3 8 carbon atoms, trifluoromethyl, {TAIL ~ nitro}, alkoxy of 1 6 carbon atoms, carboalkoxy of 2 7 carbon atoms, aralkyl of 7 10 carbon atoms, halo, dialkylamino of 1 6 carbon atoms per alkyl group, thioalkyl of 1 6 carbon atoms, or Y 
is
{ HEAD ~ X } is hydrogen , lower alkyl of 1 6 carbon atoms , cycloalkyl of 3 8 carbon atoms , trifluoromethyl , { TAIL ~ nitro } , alkoxy of 1 6 carbon atoms , carboalkoxy of 2 7 carbon atoms , aralkyl of 7 10 carbon atoms , halo , dialkylamino of 1 6 carbon atoms per alkyl group , thioalkyl of 1 6 carbon atoms , or Y
HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH