Gas-Phase Negative Ion Chemistry of Methyl Isocyanide

Article abstract of DOI:10.1021/ja00254a017

The gas-phase negative ion chemistry of methyl isocyanide (CH3NC) has been studied at 0.4 Torr in a flowing afterglow apparatus and compared with that of its isomer acetonitrile (CH3CN).Methyl isocyanide has been determined to be 1.8 +/- 0.4 kcal/mol less acidic than acetonitrile in the gas phase, yielding ΔH⁰ _acid(CH3NC) = 374 +/- 3 kcal/mol.The isocyano group has been found to stabilize an adjacent radical site better than does the cyano group.Methyl isocyanide reacts with bases by competing proton abstraction and S_N2 processes.The reaction of the isocyanomethyl anion with a number of neutral reagents has also been studied.It undergoes hydrogen-deuterium exchange with D2O while cyanide ion is a major product upon reaction with O2, SO2, N2O, COS, CS2, and C6H5CHO.Other ions are also produced in smaller amounts with many of these reagents.The rates of reaction of the isomeric anions with CH3Br have also been determined.