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