{HEAD ~ Rb} is, independently at each occurrence, C1 6 alkyl, ORa, Cl, F, Br, NRaRa1, CRa, CORa, {TAIL ~ CNRaRa1}, S2NRaRa1, NRaS2Ra3, SpRa3, or CF3 
is
{ HEAD ~ Rb } is , independently at each occurrence , C1 6 alkyl , ORa , Cl , F , Br , NRaRa1 , CRa , CORa , { TAIL ~ CNRaRa1 } , S2NRaRa1 , NRaS2Ra3 , SpRa3 , or CF3
HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH 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