• α,α-Difluoroglycine betaines synthesized under mild conditions • Structures confirmed by NMR and single-crystal X-ray diffraction • Electrostatic interactions govern crystal packing • Pyridinium betaines show enhanced thermal stability • DFT rationalizes formation mechanism and stability trends A family of α,α-difluoroglycine betaines was synthesized from potassium bromodifluoroacetate and amines under mild, anhydrous conditions. Alkylammonium and pyridinium betaines were isolated as bench-stable solids and characterized by multinuclear NMR spectroscopy and single-crystal X-ray diffraction. Crystallographic analysis revealed electrostatic interactions governing solid-state packing. Thermogravimetric analysis showed greater resistance to decarboxylation for pyridinium betaines than alkylammonium derivatives. Density functional theory calculations support an S N 2 mechanism for betaine formation and rationalize the observed stability trends. These results establish structure–stability relationships and highlight substituent-dependent effects.
Pounder et al. (Wed,) studied this question.