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—H⃛O hydrogen bond which are further interconnected in infinite zigzag chains running parallel to the a axis by N—H⃛O bonds. Weaker C—H⃛O interactions involving the methyl groups and the carboxy O atoms of the cation occur between the chains.