Crystal and molecular structure of N-methylpiperidine betaine hydrobromide

Abstract

The molecular and crystal structure of N-methylpiperidine betaine hydrobromide, MPBHBr, has been solved by X-ray diffraction methods at 100K and refined to the R=0.017 (I>2σ(I)). The crystals are monoclinic, space group P21/c, a=6.193(1), b=13.275(3), c=13.056(3)Å, β=103.38(3)°, V=1044.2(4)Å3, Z=4. Piperidine ring adopts a chair conformation with the CH2COOH group in an axial and the CH3 group in an equatorial position. The carboxylic group is engaged in a weak hydrogen bond with the bromide ion, O–H⋯Br− (Br−⋯O 3.130(1)Å). Powder FTIR spectrum was measured and assignments of the observed bands to vibrations of the hydrogen bond are proposed. In the crystal, the hydroxy proton in the COOH group is in syn conformation relative to the CO bond, while in the PM3-optimized structure it is in anti.