2 A 05 Infrared spectroscopic investigation of CH bond acidity in cationic alkanes

[Introduction] CH bonds are the most ubiquitous functional group in organic compounds. CH in a neutral molecule is generally regarded as aprotic because of its low acidity. Recently, we have demonstrated the CH bonds in the cationic ethers [1, 2] and amines [3] are highly acidic. In these cations, the acidities of CH bonds are enhanced through the hyperconjugation of the CH bond with the nonbonding orbital which is the singly occupied molecular orbital (SOMO). Alkanes are composed only of carbon and hydrogen and have no nonbonding orbital. In the ionization process to their cationic ground state, a electron is ejected. For alkane cations, therefore, we have had a question whether their CH bonds undergo acidity enhancements without the nonbonding orbital or not. In this study, to investigate the CH bond acidity in alkane cations, we perform infrared (IR) spectroscopy of n-alkane cations with different alkyl chain lengths (pentane, hexane, and heptane).