Structure, conformation and hydrogen bonding of 4-(N-methylpiperidinium)-butyric acid bromide

✍ Scribed by Z. Dega-Szafran; E. Dulewicz; M. Szafran; R. Thaimattam; M. Jaskolski

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 475 KB
• Volume: 828
• Category: Article
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2006.05.035

✦ Synopsis

A 1:1 complex between 4-(N-methylpiperidinium)-butyrate inner salt (betaine) and hydrobromide, MPBUHAEBr, has been characterized by single crystal X-ray analysis. The crystals are monoclinic, space group P2 1 /c, with a = 8.284(1), b = 10.369(1), c = 13.809(2) A ˚, b = 92.26(1)°. The piperidine ring adopts a chair conformation with the (CH 2 ) 3 COOH substituent in the axial and the CH 3 group in the equatorial positions. In the crystal, the Br À anion is engaged in a medium-strong hydrogen bond with the COOH group (OAHÁ Á ÁBr À = 3.141(1) A ˚), N + Á Á ÁBr À electrostatic interactions and in several CAHÁ Á ÁBr À contacts with the aliphatic groups forming a cavity in which it is enclosed. Three conformers (2-4) were optimized by the B3LYP/6-31G (d, p) level of theory. The most stable is conformer 4 with the (CH 2 ) 3 COOH substituent in the equatorial position and the CH 3 group in the axial position. The stability of the investigated conformers is controlled by electrostatic interactions between the oppositely charged groups. The FTIR spectrum of MPBUHAEBr shows a strong band at 2941 cm À1 due to mOH and the mC@O band at 1712 cm À1 .