Conformation of cationic N,N-dimethylglycine in dimethylglycinium trifluoroacetate

In the title compound, C4H10NO2+.C2F3O2-, the main N-C-COOH skeleton of the protonated amino acid is nearly planar. The C=O/C-N and C=O/O-H bonds are syn and the two methyl groups are gauche to the methylene H atoms. The conformation of the cation in the crystal is compared to that given by ab initio calculations (Hartree-Fock, self-consistent field molecular-orbital theory). The trifluoroacetate anion has the typical staggered conformation with usual bond distances and angles. The cation and anion form dimers through a strong O-H . . .O hydrogen bond which are further interconnected in infinite zigzag chains running parallel to the a axis by ND H . . .O bonds. Weaker C-H . . .O interactions involving the methyl groups and the carboxy O atoms of the cation occur between the chains.