Z. Dega‐Szafran, E. Dulewicz, G. Dutkiewicz
Aug 7, 2006
Citations
0
Influential Citations
7
Citations
Journal
Journal of Molecular Structure
Abstract
Abstract Bis(4-hydroxy-1-methylpiperidine betaine) hydrochloride, [bis(1-carboxymethyl-4-hydroxy-1-methylpiperidinium) hydrochloride, (HO–MPB) 2 HCl], has been prepared from stoichiometric amounts of β-4-hydroxy-1-methylpiperidine betaine hydrochloride with the OH group in an equatorial position and α-4-hydroxy-1-methylpiperidine betaine inner salt with the OH group in an axial one. Cocrystals of (HO–MPB) 2 HCl belong to monoclinic system with C 2/ c space group. Piperidinium ring has a chair conformation with the CH 2 COO group in the equatorial position and the CH 3 group in the axial one, while the OH group occupies the equatorial or axial position in the disordered structure. There are three types of substituted piperidinium molecules A , B and C in the asymmetric unit. These isomers are distributed randomly yielding partially occupied sites of the hydroxyl groups. The disorder of molecules has been confirmed by the X-ray diffraction experiments at low temperature. The piperidinium molecules form two independent homoconjugated cations, A–B and C–C , with short asymmetrical (2.457(2) A) and symmetrical (2.440(2) A) OHO hydrogen bonds, respectively. The hydroxyl groups interact with the Cl − anions by the O–H⋯Cl hydrogen bonds. The A – B cation is linked with C – C by the O–H⋯O–H hydrogen bond, while C – C cations are joined together by the O–H⋯O=C hydrogen bonds, forming infinite zigzag chains. The FTIR spectrum shows an intense νOH band in the 3300–3100 cm −1 region and a broad and intense ν(OHO) absorption in the 1500–400 cm −1 region, which confirm the presence of the O–H⋯Cl and O·H·O hydrogen bonds. The 1 H and 13 C NMR spectra, in the aqueous solution, prove the inequivalence of the piperidinium ring caused by two conformations of the OH group at the ring.