{HEAD ~ R11} is independently selected from {TAIL ~ the group} consisting of alkyl and aryl; and 
is independently selected from
{ HEAD ~ R11 } is independently selected from { TAIL ~ the group } consisting of alkyl and aryl ; and
HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH