The Kinetics of the Thermal Isomerization of Cinnamic Acid Catalyzed by Iodine

Dickinson, Roscoe G.; Lotzkar, H.

doi:10.1021/ja01282a013

Cited by 24 publications

(5 citation statements)

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“…The energy of activation was found to be approximately 24 kcal. (30). These observations support the theory that had been previously proposed, suggesting that the halogen-catalyzed isomerization of unsaturated acids probably takes place through catalysis by halogen atoms (5).…”

Section: J¡supporting

confidence: 89%

The Cis-Trans Isomerization of Conjugated compounds

Wyman¹

1955

Chem. Rev.

145

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Section: J¡supporting

confidence: 89%

The Cis-Trans Isomerization of Conjugated compounds

Wyman¹

1955

Chem. Rev.

145

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“…The ability of iodine to speed the equilibration of alkenes has been known since the 19th century. 1 In the 1960s, Benson and co-workers exploited this reaction in the gas phase to obtain accurate relative energies of alkenes; 2 their initial work on butene revealed both positional (hydrogen-shift) [3][4][5][6] and geometrical (cis/trans) [3][4][5]7 isomerism. Back and Cvetanovic investigated the gas-phase butene reactions as well, at milder temperatures.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Cis/Trans Equilibration of Alkenes via Iodine Catalysis

Hepperle

East

2005

J. Phys. Chem. A

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Iodine is commonly used to speed the equilibration of Wittig cis/trans alkene products. This study uses computational chemistry to study the catalyzed isomerization mechanism in detail for seven different examples of 1,2-disubstituted alkenes. We find that the iodo intermediates of the conventional three-step reaction path are weakly stable, bound by less than 7 kJ mol(-1) in five cases and nonexistent in the other two. These variations in relative stability appear to be closely related to the degree of conjugation interruption in the alkene upon attachment of iodine. The rate-determining reaction barrier always occurs in the middle step, the internal rotation of the iodo intermediate, and the variations in the barrier heights are dictated by varying levels of steric hindrance in the seven cases. Regiospecificity of I-atom addition and noticeable hyperconjugative effects are discussed. Comparisons between various theoretical approximations are performed to demonstrate the great difficulty in obtaining accurate results for iodine-atom bond-forming and bond-breaking energies.

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“…Contemporary studies by Liebermann in 1890 observed the quantitative conversion of Z ‐ to E ‐cinnamic acid upon addition of iodine at reflux in CS 2 . Predicated on the dissociation of iodine (thermal or photochemical) and addition of the iodine radical to the alkene, this general strategy to allow for the Z → E isomerisation of olefins is of practical value in contemporary synthesis. Similarly, elemental selenium or the photochemical generation of a radical cation intermediate, which propagate in a chain‐like mechanism, provide efficient routes to E ‐stereoisomers.…”

Section: Geometrical Isomerisationmentioning

confidence: 96%

Positional and Geometrical Isomerisation of Alkenes: The Pinnacle of Atom Economy

2019

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Strategies to achieve spatiotemporal regulation of pre‐existing alkenes via external stimuli are essential given the ubiquity of feedstock olefins in chemistry and their downstream applications. Mirroring the 1‐0 switch that underpins mammalian vision through selective geometric isomerisation in retinal, strategies to manipulate 2D space by both geometric and positional isomerisation of alkenes via chemical, thermal and light‐driven processes are being intensively pursued. This minireview highlights the current state of the art in activating and achieving directionality in these fundamental chemical transformations.

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The Kinetics of the Thermal Isomerization of Cinnamic Acid Catalyzed by Iodine

Cited by 24 publications

References 0 publications

The Cis-Trans Isomerization of Conjugated compounds

The Cis-Trans Isomerization of Conjugated compounds

Mechanism of Cis/Trans Equilibration of Alkenes via Iodine Catalysis

Positional and Geometrical Isomerisation of Alkenes: The Pinnacle of Atom Economy

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