The precursor is relatively reactive under {HEAD ~ one set} of {TAIL ~ conditions} and is relatively non reactive under another set of conditions 
of
The precursor is relatively reactive under { HEAD ~ one set } of { TAIL ~ conditions } and is relatively non reactive under another set of conditions
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH