{HEAD ~ R11} and R12 are {TAIL ~ each}, independently, hydrogen, alkyl of 1 6 carbon atoms, aralkyl of 7 10 carbon atoms, cycloalkyl of 3 8 carbon atoms, halogen, or trifluoromethyl 
are
{ HEAD ~ R11 } and R12 are { TAIL ~ each } , independently , hydrogen , alkyl of 1 6 carbon atoms , aralkyl of 7 10 carbon atoms , cycloalkyl of 3 8 carbon atoms , halogen , or trifluoromethyl
HEAD HEAD HEAD HEAD HEAD OTH OTH REL 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