On the mechanism of a modified Perkin condensation leading to α-phenylcinnamic acid stereoisomers - Experiments and molecular modelling

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Abstract

A modified Perkin condensation leading to α-phenylcinnamic acid stereoisomers affords predominantly or exclusively the (E)-isomer. Reaction duration, temperature, and polarity of the solvent affect the isomeric distribution only to a minor extent. However, geometry optimization of the stereoisomers by semiempirical quantum chemical methods revealed that their thermodynamic stabilities in the absolute minimum are the same. (E)-(Z)-isomerization under the conditions of the Perkin condensation resulted in an equilibrium mixture of nearly 1:1 composition, thus corroborating the results of the computations. Comparing the detailed potential energy maps of the isomers obtained at the semiempirical level of theory may explain the controversy. The (Z)-isomer has a structured potential energy surface with few but well-defined minima, whereas that of the (E)-isomer shows an extended flat plateau enabling this isomer to approach a minimum (which is close to the global one) right after its formation.

Original languageEnglish
Pages (from-to)1097-1104
Number of pages8
JournalMonatshefte fur Chemie
Volume131
Issue number10
Publication statusPublished - 2000

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Stereoisomerism
Molecular modeling
Isomers
Condensation
Acids
Experiments
Potential energy surfaces
Isomerization
Potential energy
Thermodynamic stability
Geometry
Chemical analysis
Temperature

Keywords

  • Isomeric distribution
  • Potential energy surfaces
  • Semiempirical quantum chemical methods
  • Stereoselectivity

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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title = "On the mechanism of a modified Perkin condensation leading to α-phenylcinnamic acid stereoisomers - Experiments and molecular modelling",
abstract = "A modified Perkin condensation leading to α-phenylcinnamic acid stereoisomers affords predominantly or exclusively the (E)-isomer. Reaction duration, temperature, and polarity of the solvent affect the isomeric distribution only to a minor extent. However, geometry optimization of the stereoisomers by semiempirical quantum chemical methods revealed that their thermodynamic stabilities in the absolute minimum are the same. (E)-(Z)-isomerization under the conditions of the Perkin condensation resulted in an equilibrium mixture of nearly 1:1 composition, thus corroborating the results of the computations. Comparing the detailed potential energy maps of the isomers obtained at the semiempirical level of theory may explain the controversy. The (Z)-isomer has a structured potential energy surface with few but well-defined minima, whereas that of the (E)-isomer shows an extended flat plateau enabling this isomer to approach a minimum (which is close to the global one) right after its formation.",
keywords = "Isomeric distribution, Potential energy surfaces, Semiempirical quantum chemical methods, Stereoselectivity",
author = "I. P{\'a}link{\'o} and {\'A}. Kukovecz and B{\'e}la T{\"o}r{\"o}k and T. K{\"o}rtv{\'e}lyesi",
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T1 - On the mechanism of a modified Perkin condensation leading to α-phenylcinnamic acid stereoisomers - Experiments and molecular modelling

AU - Pálinkó, I.

AU - Kukovecz, Á.

AU - Török, Béla

AU - Körtvélyesi, T.

PY - 2000

Y1 - 2000

N2 - A modified Perkin condensation leading to α-phenylcinnamic acid stereoisomers affords predominantly or exclusively the (E)-isomer. Reaction duration, temperature, and polarity of the solvent affect the isomeric distribution only to a minor extent. However, geometry optimization of the stereoisomers by semiempirical quantum chemical methods revealed that their thermodynamic stabilities in the absolute minimum are the same. (E)-(Z)-isomerization under the conditions of the Perkin condensation resulted in an equilibrium mixture of nearly 1:1 composition, thus corroborating the results of the computations. Comparing the detailed potential energy maps of the isomers obtained at the semiempirical level of theory may explain the controversy. The (Z)-isomer has a structured potential energy surface with few but well-defined minima, whereas that of the (E)-isomer shows an extended flat plateau enabling this isomer to approach a minimum (which is close to the global one) right after its formation.

AB - A modified Perkin condensation leading to α-phenylcinnamic acid stereoisomers affords predominantly or exclusively the (E)-isomer. Reaction duration, temperature, and polarity of the solvent affect the isomeric distribution only to a minor extent. However, geometry optimization of the stereoisomers by semiempirical quantum chemical methods revealed that their thermodynamic stabilities in the absolute minimum are the same. (E)-(Z)-isomerization under the conditions of the Perkin condensation resulted in an equilibrium mixture of nearly 1:1 composition, thus corroborating the results of the computations. Comparing the detailed potential energy maps of the isomers obtained at the semiempirical level of theory may explain the controversy. The (Z)-isomer has a structured potential energy surface with few but well-defined minima, whereas that of the (E)-isomer shows an extended flat plateau enabling this isomer to approach a minimum (which is close to the global one) right after its formation.

KW - Isomeric distribution

KW - Potential energy surfaces

KW - Semiempirical quantum chemical methods

KW - Stereoselectivity

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