{HEAD ~ R3} is {TAIL ~ H}, SO3 X, halogen, CN, NO2, or L SC  
is
{ HEAD ~ R3 } is { TAIL ~ H } , SO3 X , halogen , CN , NO2 , or L SC
HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH