{TAIL ~ A} is halogen, phenyl, Sm phenyl, or {HEAD ~ NR5R6} 
{ TAIL ~ A } is halogen , phenyl , Sm phenyl , or { HEAD ~ NR5R6 }
TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD