Could the reactions of formic acid with CH3NH2+/CH3NH3+ produce protonated glycine?

A theoretical study of the reactions of CH3NH2+/CH3NH3+ with formic acid has been carried out in order to clarify their role in the formation of glycine derivatives under the conditions of the interstellar medium. The possible intermediate species as well as the relevant transition states for these reactions were characterized at the MP2 level with the cc-pVTZ basis set. Energetic data were obtained at the CCSD(T) level employing the aug-cc-pVTZ basis set. Formation of protonated glycine is an exothermic process for the reaction of formic acid with CH3NH2+ (−2.5 kcal/mol at the CCSD(T) level) and a quasi-isoenergetic one for its reaction with CH3NH3+ (2.9 kcal/mol at the CCSD(T) level). However, in both cases a net activation barrier is found, suggesting that both processes are not allowed under interstellar conditions.

Graphical abstractEnergy profile, in kcal/mol, for the reaction of CH3NH2+ with HCOOH at the CCSD(T)/aug-ccpVTZ and MP2/cc-pVTZ (in parentheses) levels. Zero-point vibrational energy differences are included.Figure optionsDownload full-size imageDownload high-quality image (219 K)Download as PowerPoint slide