Molecular structure, hydrogen bonding and spectroscopic properties of the complex of piperidine-4-carboxylic acid with chloroacetic acid

Abstract

Complex of piperidine-4-carboxylic acid with chloroacetic acid has been studied by X-ray diffraction, FTIR, Raman, 1 H and 13 C NMR spectroscopy and B3LYP/6-31G(d,p) calculations. In crystal the piperidine ring is protonated and adopts a chair conformation with the COOH group in the equatorial position. The COO À group of chloroacetate unit is engaged in three hydrogen bonds: O(1)-H(1)ÁÁÁO(3) of 2.604(2) Å , N(1)-H(12)ÁÁÁO(3) of 2.753(2) Å and N(1)-H(11)ÁÁÁO(4) of 2.760(2) Å. According to the B3LYP calculations the isolated complexes both in vacuum and H 2 O solution have cyclic structures. In vacuum the molecules are connected by two H-bonds: the COOH group of chloroacetic acid is engaged with piperidine-4-carboxylic acid, one with the nitrogen atom, O(4)-HÁÁÁN(1) of 2.658 Å and the second with carboxyl group, O(1)-HÁÁÁO(3) of 2.860 Å. In water solution piperidine-4-carboxylic acid is protonated and forms two hydrogen bonds with the chloroacetate unit: N(1)-HÁÁÁO(4) of 2.690 Å and O(1)-HÁÁÁO(3) of 2.611 Å. Powder FTIR spectra of the complex and its deuterated analogue are consistent with the X-ray structure. Correlations between the experimental 1 H and 13 C chemical shifts of the complex investigated and the GIAO/B3LYP/6-31G(d,p) calculated magnetic isotropic shielding tensors (r calc) in vacuum and within the conductor-like screening continuum solvation model (COSMO) in H 2 O, d exp = a + b r calc , are reported.

Theoretical and experimental vibrational spectroscopic study of 4-(1-Pyrrolidinyl)piperidine

“…After much controversy during the 1950s-1970s, the equatorial conformation was found to be more stable by 0.72 kcal/mol in the gas phase [14]. Substituents on a piperidine ring have been found in the equatorial position [14,15].…”

<b>Experimental and theoretical NMR study of 4-(1-pyrrolidinyl)piperidine</b>

“…After much controversy during the 1950s-1970s, the equatorial conformation was found to be more stable by 0.72 kcal/mol in the gas phase [1]. Substituents on a piperidine ring have been found in the equatorial position [1,2]. Pyrrolidine is expected the pure envelope conformation with apex at the N-atom and the pure twist conformation [3].…”

Spectroscopic studies of the 1:1 complex of piperidine-4-carboxylic acid (isonipecotic acid) with 2,6-dichloro-4-nitrophenol

“…Piperidine-4-carboxylic acid in its zwitterionic form has two interacting centers, the proton-donor N + H2 group and the proton-acceptor COO -group, which are characterized by the dissociation constants of 10.33 and 3.86, respectively [8], hence P4C is able to form hydrogen-bonded complexes with inorganic [9,10] and organic acids [11][12][13].…”