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2 Polish Journal of Chemistry

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Crystal and Molecular Structure of 1:1 Complex Between Piperidine-3-carboxylic Acid and p-Hydroxybenzoic Acid Studied by X-ray Diffraction, FTIR, 1H and 13C NMR Spectroscopy, and B3LYP Method

Dega-Szafran Z., Jaskólski M., Szafran M.

Polish Journal of Chemistry

2007

Vol. 81, nr 5-6

931-946

A1:1 complex between the zwitterionic piperidinium-3-carboxylate (P3C) and p-hydroxybenzoic acid (HBA), P3C.HBA, has been characterized by single crystal X-ray analysis. The crystals are orthorhombic, space group Pbca, with a = 11.913(1), b = 9.407(1), c = 22.124(2) capital A, ring. There is a short O–HźźźO bridge (2.507(2) capital A, ring) connecting P3C with HBA. The proton is located at the benzoic acid carboxylate but the O–H bond is elongated (1.08capital A, ring) and the geometry of the COO groups suggests a nearly equivalent participation in this strong hydrogen bond. The piperidine ring adopts a chair conformation. The bulky carboxylate substituent takes an axial orientation in which it is stabilized by an intramolecular N+–HźźźO bond (2.880(2) capital A, ring). In the crystal packing, the P3CHBA units are connected with crystallographic neighbors by hydrogen bonds that involve only molecules of the same type. In this system of interactions, a zwitterionicmolecule attracts two zwitterionic neighbors via its two N+–H2 donors (accepted by the alternateO atoms of the carboxylate group; 2.823(2) and 2.841(2) ), while an aromatic molecule is connected to another aromatic molecule via a hydrogen bond of length 2.655(2) capital A, ring, involving the para-hydroxyl donor and the carbonyl acceptor of the carboxylic group. In a model optimized by the B3LYP/6-31G(d,p) method, P3C in its neutral form interacts via a C=OźźźHOOC hydrogen bond with HBA. The FTIR spectrum shows a broad absorption in the 3100–2400 cm–1 region attributed to niNH and niOH vibrations. The broad absorption in the 1495–910 cm–1 region is attributed to the short O(3)–HźźźO(1) hydrogen bond (niOH and gammaOH). The 1H and 13C NMR spectra have been analyzed to elucidate the complex structure in solution.

Two Independent Hydrogen Bonded Complexes of Bis(1-piperidiniumacetate) Hydrochloride in the Crystal and in the PM3 Optimized Structure

Dega-Szafran Z., Petryna M., Dutkiewicz G., Kosturkiewicz Z.

Polish Journal of Chemistry

2003

Vol. 77 / nr 11

1501-1512

Bis(1-piperidiniumacetate) hydrochloride, (PAA)2H+źCl-, has been synthesized and its structure solved by X-ray diffraction. The crystals belong to the triclinic system with two symmetrically independent hydrogen bonded complexes, denoted A and B, at two different inversion centers. The compound crystallizes in the space group P1 with a = 8.559(1), b = 9.625(1), c = 11.441(1) A, _ = 74.85(1)°, _= 68.22(1)°, _ = 84.10(1)°, Z = 2, R = 0.036. Each complex consists of two 1-piperidiniumacetate moieties. Four 1-piperidiniumacetates, as zwitterions, are held together by a network of hydrogen bonds of the types OźźźHźźźO (2.462(3) and 2.463(3) A), N-HźźźO (2.755(2) A) and N-HźźźCl (3.167(2)A). Both N-H atoms in complex A interact with chlorine anions. A number of week C-HźźźCl contacts stabilize the three-dimensional crystal structure. In the isolated molecule of (PAA)2H+źCl- optimized by the PM3 method, there also are two independent hydrogen bonded complexes. In complex A the neutral form of 1-piperidineacetic acid interacts with its anionic form, while in complex B the 1-piperidiniumacetic acid, as a cation, forms a hydrogen bond with its zwitterionic form. FTIR spectrum of bis(1-piperidiniumacetate) hydrochloride has been analyzed and discussed.