{HEAD ~ The reaction time} required may depend upon {TAIL ~ various factors} including the mole ratio of compounds and and the nature of organic groups R2 and R3 and may generally be in the range of 5 30 minutes 
depend upon
{ HEAD ~ The reaction time } required may depend upon { TAIL ~ various factors } including the mole ratio of compounds and and the nature of organic groups R2 and R3 and may generally be in the range of 5 30 minutes
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH