R6 and R9 are each, independently, hydrogen, {TAIL ~ alkyl} of {HEAD ~ 1 6 carbon atoms}, or aralkyl of 7 10 carbon atoms 
R6 and R9 are each , independently , hydrogen , { TAIL ~ alkyl } of { HEAD ~ 1 6 carbon atoms } , or aralkyl of 7 10 carbon atoms
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH