## Abstract The presence of two diastereoisomeric thiazolidines obtained by the reaction of L‐cysteine or L‐cysteine ethyl ester and pyridoxal or pyridoxal‐5‐phosphate is demonstrated by ^1^H and ^13^CNMR spectroscopy. Fast interconversion of isomers occurs in neutral or alkaline solution.
Trans-cis isomerization of 4-(2-(9-anthryl)vinyl)pyridine. Molecular structures and 1H NMR kinetic studies
✍ Scribed by Ya-Yin Choi; Wai-Yeung Wong; Wing-Tak Wong
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 422 KB
- Volume
- 17
- Category
- Article
- ISSN
- 0256-7660
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✦ Synopsis
Abstract
Both cis‐ and trans‐isomers of 4‐(2‐(9‐anthryl) vinyl) pyridine were isolated and their molecular structures established by X‐ray crystallographic method. Variable temperature ^1^H NMR spectroscopy was used to study the trans to cis isomerization of the title compound. The kinetic study of the reaction was based on the ratio of the NMR integration heights in toluene‐d~8~ of the double doublet due to the cis‐isomer at δ 8.51 to that of the multiplet at δ 8. 15 which was kept constant during the whole experiment. The isomerization process was found to be first order and the Arrhenius activation parameters E~8~, ln A, Δ H^≠^ and ΔS^≠^ were calculated as 27.84 kJ/mol, 6.71, 25.23 kJ/mol and −197.89 J/(K·mol), respectively. Besides, conformational analyses of both compounds based on molecular modeling were carried out and the results were used to compare with the experimental data.
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