What makes hydrocyanic acid a normal acid?

Abstract

A classical intersecting-state model is applied to the study of proton-transfer reactions of HCN with oxygen and nitrogen bases. According to theory, what makes these proton transfer fast processes is the involvement of the CN bond together with the XH bonds in the reaction co-ordinate, which increases the average bond order of the transition state and decreases the reaction energy barrier. The slow reactions of most carbon acids and the intermediate behaviour of some other carbon acids such as the malononitriles and ethyl vinyl ether are also discussed within this theoretical formalism.