Preferably {HEAD ~ the alkylene group} has {TAIL ~ one to ten carbon atoms}, preferably one to six carbon atoms, and preferably is a methylene group, —CH2— 
has
Preferably { HEAD ~ the alkylene group } has { TAIL ~ one to ten carbon atoms } , preferably one to six carbon atoms , and preferably is a methylene group , — CH2 —
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH