1073. Thiocyanogen, thiocyanates, and isothiocyanates. Part III. Substitution reactions of triphenylmethyl isothiocyanate with acids and salts

Abstract

The reported substitutions are of the type PhsCeNCS --f Ph3CX and probably involve the ion Ph&+ as an intermediate. In strong acids, the isothiocyanate undergoes protonation and ionic dissociation, and gives the alcohol on addition of water; its dissociation is complete in concentrated sulphuric acid. Triphenylmethanol or its carboxylic esters are obtained from solutions in some carboxylic acids, but formic acid eventually causes complete reduction to triphenylmethane, whilst trifluoroacetic acid gives some triphenylmethylamine ; thiolcarboxylic acids give good yields of their triphenylmethyl esters. Observations on the reversibility of hydrolysis and alcoholysis of triphenylmethyl isothiocyanate are reported. The appropriate alkali-metal salts in organic solvents effect the substitutions, Ph&NCS + M X +Ph&X (X = OH, OMe, CN, N3, SCOR) ; the iodide, thus obtained, undergoes homolysis. The ready substitution reactions of triphenylmethyl isothiocyanate with solutions of silver nitrate, silver perchlorate, silver salts of carboxylic acids, and ferric chloride exemplify the assistance afforded by a transition-metal ion, but much more drastic conditions are needed for reaction with silver cyanide or mercuric cyanide.MOBILITY of the substituent group in organic thiocyanates is known chiefly with respect to the isomerisation reaction, for which there is evidence2 of ionisation as the intermediate step: