3 Methyl 2 butanol is difficult to separate from 1 butanol by conventional distillation or rectification because of {HEAD ~ the proximity} of {TAIL ~ their boiling points} 
3 Methyl 2 butanol is difficult to separate from 1 butanol by conventional distillation or rectification because of { HEAD ~ the proximity } of { TAIL ~ their boiling points }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL