{HEAD ~ R2} is {TAIL ~ hydrogen}, nitro, amino or mono or dialkylamino; and 
is
{ HEAD ~ R2 } is { TAIL ~ hydrogen } , nitro , amino or mono or dialkylamino ; and
HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH