The reaction is conveniently carried out in an inert organic solvent in the presence of a catalytic amount of {HEAD ~ an organic or inorganic acid} such as p toluenesulphonic acid or {TAIL ~ dry hydrochloric acid} 
such as
The reaction is conveniently carried out in an inert organic solvent in the presence of a catalytic amount of { HEAD ~ an organic or inorganic acid } such as p toluenesulphonic acid or { TAIL ~ dry hydrochloric acid }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL