Dediazoniation of Arenediazonium Ions. Part XIX. Effect of thiocyanate ion in the reactions of 2,4,6‐trimethylbenzenediazonium tetrafluoroborate in 2,2,2‐trifluoroethanol

The dediazoniation of 2,4,6‐trimethylbenzenediazonium tetrafluoroborate ( 1 ) in 2,2,2‐trifluoroethanol (TFE) was studied in the presence of potassium thiocyanate. The effect of added salt on the dediazoniation rate, the N α ‐N β rearrangement ( Eqn. 2 ), the exchange of the 15 N‐labelled diazo group with molecular nitrogen ( Eqn. 3 ), and the reaction products was determined. With 0.3 M KSCN a dediazoniation‐rate increase of 16.5% was achieved, and the amounts of rearranged and exchanged product were reduced to 88% and 70%, respectively, of the values found in pure TFE. The dediazoniation products formed are ArF ( 3 ), ArOCH 2 CF 3 ( 4 ), ArSCN ( 5 ), ArNCS ( 6 ) and traces of 5, 7‐dimethylindazole ( 7 ). All the data are in agreement with, and support the previously proposed mechanism ( Equ. 1 ) of heterolytic dediazoniation of arenediazonium salts.