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Determination of the 2,3‐pentadienedioic acid enantiomer interconversion energy barrier 1. Classical kinetic approach
Author(s) -
Májek Pavel,
Mydlová Janka,
Krupcík Jan,
Lehotay Jozef,
Armstrong Daniel. W.,
Cotton F. Albert
Publication year - 2006
Publication title -
journal of separation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.72
H-Index - 102
eISSN - 1615-9314
pISSN - 1615-9306
DOI - 10.1002/jssc.200600159
Subject(s) - enantiomer , chemistry , kinetic energy , ab initio , computational chemistry , kinetics , reaction rate constant , high performance liquid chromatography , ab initio quantum chemistry methods , racemic mixture , stereochemistry , thermodynamics , molecule , chromatography , organic chemistry , physics , quantum mechanics
A classical kinetic method was used to determine the energy barrier for the interconversion of 2,3‐pentadienedioic acid enantiomers. Each individual enantiomer was isolated by collecting the appropriate peaks from the HPLC enantiomeric separation, of racemic 2,3‐pentadienedioic acid. The isolated enantiomers were racemized at 22°C using various interconversion times. The ratio of enantiomers in each reaction solution was determined by HPLC at 22°C. The corresponding peak areas of the enantiomers and the interconversion times obtained from the HPLC chromatograms were used to calculate both the interconversion rate constants describing (+) → (–) and (–) → (+) interconversions as well as the energy barriers. It was confirmed that the interconversion of 2,3‐pentadienedioic acid enantiomers is a first‐order kinetic reaction. Both semiempirical and ab initio methods were used to explore the mechanism of the interconversion of 2,3‐pentadienedioic acid enantiomers, and to calculate the interconversion energy barrier. Comparison of the interconversion energy barriers found by the ab initio method (Δ G # = 110.7 kJ/mol) and by classical kinetics in the mobile phase solution at 22°C (Δ G app = 93.9 ± 0.2 kJ/mol) shows a difference which may be attributed to the different conditions assumed in the theoretical calculation ( i. e. , a gaseous state) and the actual experimental conditions ( i. e. , liquid solution) and a possible catalytic effect of the solution composition.