Ion Chemistry of Cyanides and Isocyanides. 2. Alkylation of HCN and Cyanides by Oxygen and Sulfur Compounds. Gas-Phase Synthesis and Reactions of Protonated Isocyanides

Article abstract of DOI:10.1021/j100401a042

The reaction ROH2(1+) + HCN -> RNCH(1+) + H2O is observed in mixtures containing alcohols and HCN.Proton affinity bracketing experiments show that the products are protonated isocyanides, RNCH(1+), which are formed by alkylation of the nitrogen in HCN, rather than protonated cyanides, RCNH(1+).Although the latter are more stable, their production would require rearrangement.Similar reactions are observed between (CH3)2OH(1+) and RSH2(1+) and HCN.CH3CN and HC3N (cyanoacetylene) can also be alkylated in similar fashion to form the nitrilium ions CH3CNCH3(1+) and HC3NCH3(1+), respectively.In cases where the proton affinity of the nitrile is higher than that of the alcohol, alkylation occurs by a condensation reaction, such as in methanol and acetonitrile: CH3CNH(1+) + CH3OH -> CH3NCCH3(1+) + H2O.The rate constants for the alkylation reactions are generally in the range of (1-10) E-11 cm³ s^-1 and are not affected significantly by the reaction exothermicity or by the structure of the reactants.These reactions may contribute to the synthesis of isocyanides in interstellar clouds and planetary atmospheres.