FOURIER-TRANSFORM INFRARED-SPECTROSCOPY STUDIES OF CYANIDE ION SOLUTIONS OF DIMETHYLFORMAMIDE AND AQUEOUS DIMETHYLFORMAMIDE

Fourier transform infrared spectroscopy has been used to investigate t he behaviour of HCN and alkali metal and tetraethylammonium cyanides i n DMF and aqueous DMF. The cyanide ion exists as free ions and ion pai rs in pure DMF but as water-solvated and DMF-solvated ions in aqueous DMF. The aqueous DMF solutions can be treated as a pseudo two-phase sy stem with a distribution coefficient of 0.018 between the aqueous and DMF-rich pseudo phases. A kinetic analysis of the cyanide ion - benzyl chloride reaction in DMF and aqueous DMF has shown that the rate cons tant for the S(N)2 reaction is markedly decreased with the addition of as little as 2.5% water. This decrease is primarily due to changes in transition state solvation. The S(N)2 reactions between cyanide ion a nd benzylmethyl-4-substituted phenylsulphonium perchlorates in 20% aqu eous DMF have also been investigated.