The catalyst may be {HEAD ~ any} of the dialkyl substituted {TAIL ~ aromatic amines}, preferably N,N dimethylparatoluidine or N,N diisopropylparatoluidine 
The catalyst may be { HEAD ~ any } of the dialkyl substituted { TAIL ~ aromatic amines } , preferably N , N dimethylparatoluidine or N , N diisopropylparatoluidine
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH