Protonation of γ-Butyrolactone and γ-Butyrolactam

γ-Butyrolactone and γ-butyrolactam were reacted in the superacidic systems XF/MF₅ (X=H, D; M=As, Sb). Salts of the monoprotonated species of γ-butyrolactone were obtained in terms of [(CH₂ )₃ OCOH]⁺ [AsF₆ ]^- , [(CH₂ )₃ OCOH]⁺ [SbF₆ ]^- and [(CH₂ )₃ OCOD]⁺ [AsF₆ ]^- and the analogous lactam salts in terms of [(CH₂ )₃ NHCOH]⁺ [AsF₆ ]^- , [(CH₂ )₃ NHCOH]⁺ [SbF₆ ]^- and [(CH₂ )₃ NDCOD]⁺ [AsF₆ ]^- . The salts were characterized by low temperature Raman and infrared spectroscopy and for both protonated hexafluoridoarsenates, [(CH₂ )₃ OCOH]⁺ [AsF₆ ]^- and [(CH₂ )₃ NHCOH]⁺ [AsF₆ ]^- , 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.