EXPERIMENTAL-STUDY OF HCN+ AND HNC+ ION CHEMISTRY

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 12cm3 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 ∆Hf(HNC+) < 1373 kJ mol-1, and hence PA(CN at N) > 595 kJ mol-1. © 1990, American Chemical Society. All rights reserved.