Experimental study of HCN+ and HNC+ ion chemistry

Article abstract of DOI:10.1021/ja00176a006

We report the results of a room temperature selected ion flow tube study of reactions of HCN⁺ and HNC⁺. Electron impact on HCN was found to produce a mixture of HCN⁺ and HNC⁺ isomers. HCN⁺ was found to be isomerized efficiently to HNC⁺ by reaction with CO or with CO₂, and isomerization is expected to occur for any other species M having a proton affinity PA(CN at C) < PA(M) < PA(CN at N). The isomerization process is interpreted in terms of a forth and back proton transfer mechanism. A monitor gas technique was used to distinguish between the isomers. With CF4, HCN⁺ was reactive (k = 1.2 × 10^-9 cm³ s^-1) and HNC⁺ unreactive. With SF₆ both isomers react at the collision rate but HCN⁺ yields only SF₅⁺ as the product ion whereas HNC⁺ yields only HNCF⁺. Thermodynamic data established in this work include Δ_r(HNC⁺) ≤ 1373 kJ mol^-1, and hence PA(CN at N) ≥ 595 kJ mol^-1.