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