a straight chain or branched {HEAD ~ alkyl group} with {TAIL ~ 1 6 C atoms}, 
with
a straight chain or branched { HEAD ~ alkyl group } with { TAIL ~ 1 6 C atoms } ,
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH