Protonation of γ‐Butyrolactone and γ‐Butyrolactam

Abstract: γ‐Butyrolactone and γ‐butyrolactam were reacted in the superacidic systems XF/MF(5) (X=H, D; M=As, Sb). Salts of the monoprotonated species of γ‐butyrolactone were obtained in terms of [(CH(2))(3)OCOH](+)[AsF(6)](−), [(CH(2))(3)OCOH](+)[SbF(6)](−) and [(CH(2))(3)OCOD](+)[AsF(6)](−) and the analogous lactam salts in terms of [(CH(2))(3)NHCOH](+)[AsF(6)](−), [(CH(2))(3)NHCOH](+)[SbF(6)](−) and [(CH(2))(3)NDCOD](+)[AsF(6)](−). The salts were characterized by low temperature Raman and infrared spectroscopy and for both protonated hexafluoridoarsenates, [(CH(2))(3)OCOH](+)[AsF(6)](−) and [(CH(2))(3)NHCOH](+)[AsF(6)](−), single‐crystal X‐ray structure analyses were conducted. In addition to the experimental results, quantum chemical calculations were performed on the B3LYP/aug‐cc‐pVTZ level of theory. As in both crystal structures C⋅⋅⋅F contacts were observed, the nature of these contacts is discussed with Mapped Electrostatic Potential as a rate of strength.