Preferably, the completion of reaction should be confirmed by {HEAD ~ the usual means} such as {TAIL ~ 1 HNMR spectrometry} 
Preferably , the completion of reaction should be confirmed by { HEAD ~ the usual means } such as { TAIL ~ 1 HNMR spectrometry }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL