M. Szafran, Z. Dega‐Szafran, M. Jaskólski
May 2, 2005
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0
Influential Citations
11
Citations
Journal
Journal of Molecular Structure
Abstract
Abstract The crystal structure of the 2:1 (basic) salt of N -methylpiperidine betaine (zwitterionic molecule) with hydrochloric acid (MPB) 2 H·Cl, reveals that the N -methylpiperidine betaine units are hemiprotonated and form a dimeric cation through a short O·H·O hydrogen bond of 2.446(2) A. The piperidine ring has a chair conformation with the methyl group in the axial and the –CH 2 COO substituent in the equatorial position. The Me–N + –CH 2 –COO unit has a gauche conformation. The investigated complex is isomorphous with (MPB) 2 H·Br and pseudo-isomorphous with (MPB) 2 H·I. The short hydrogen bond is described by a symmetrical double-minimum potential. The halide anions form weak C–H⋯X − hydrogen bonds with the N + –CH 2 and N + –CH 3 groups. A linear relation exists between the C–H⋯X − distance and the halide ionic radius. Eight conformers of the [(MPB) 2 H] + cation and three conformers of the anion formed by (1-methyl-cyclohexyl)acetate units, [(MCHA) 2 H] − , were analyzed by the B3LYP/6-31G(d,p) level of theory in order to investigate the effect of the N + ⋯O electrostatic interactions on the conformation of MPB and on the short O·H·O hydrogen bond. The effect of the counter-ions on the FTIR and NMR spectra of the (MBP) 2 H·X complexes is also discussed.