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All 2 posts   Subject: Epoxidation and Hydroxylation with Peracids   Please login to post   Down

 
    Rhodium
(Chief Bee)
01-10-04 22:26
No 481655
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      Epoxidation and Hydroxylation with Peracids
(Rated as: excellent)
    

Epoxidation and Hydroxylation of Alkenes with Organic Peracids
Daniel Swern
Organic Reactions, Vol. 7, Ch. 7, pp 378-433 (1953) (https://www.rhodium.ws/pdf/peracid.oxidation.or7.pdf)

Contents

Introduction
Scope
Epoxidation
Hydroxylation
Stereochemistry and Mechanism
Selection of Experimental Conditions
Experimental Procedures
Analysis of Peracids
Preparation of Peracids
Perbenzoic Acid
Monoperphtalic Acid
Peracetic Acid
Performic Acid
Epoxidation with Perbenzoic Acid
Epoxidation with Monoperphtalic Acid
Hydroxylation with Hydrogen Peroxide-Acetic Acid
Hydroxylation with Hydrogen Peroxide-Formic Acid
Hydroxylation with Performic Acid
Table I: Alkenes Oxidized with Organic Peracids
A. Hydrocarbons
B. Steroids
C. Acids
D. Alcohols
E. Esters
F. Aldehydes and Ketones
G. Ethers
H. Miscellaneous
References

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    Rhodium
(Chief Bee)
10-11-04 16:22
No 535362
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      Mechanism of the Peracid Epoxidation of Alkenes
(Rated as: good read)
    

Mechanism of Acid-Catalyzed Epoxidation of Alkenes with Peroxy Acids
Robert D. Bach, Carlo Canepa, Julia E. Winter and Paul E. Blanchette
J. Org. Chem. 62, 5191-5197 (1997) (https://www.rhodium.ws/pdf/peracid.epoxidation.mechanism.pdf)

Abstract
A 6.8 fold increase in the rate of epoxidation of (Z)-cyclooctene with m-chloroperbenzoic acid is observed upon addition of the catalyst trifluoroacetic acid. Kinetic and theoretical studies suggest that this increase in rate is due to complexation of the peroxy acid with the undissociated acid catalyst (HA) rather then protonation of the peroxy acid. The transition structure for oxidation of ethylene with protonated peroxyformic acid exhibits a spiro orientation of the electrophilic oxygen at the QCISD/6-31G(d) level and the complexed peroxy acid (HCO3H·HA) transition state is also essentially spiro at the ab initio and density functional levels. At the B3LYP/6-311G(d,p) level the protonated transition structure exhibits a more planar approach where the O3-H9 of the peroxy acid lies in the plane of the π-system of ethylene, and the barrier for formation of protonated oxirane is only 4.4 kcal·mol-1. Epoxidation with neutral and complexed peroxyformic acid also involves a symmetrical spiro orientation affording an epoxide, and the barriers for formation of oxirane at the same level are 14.9 kcal·mol-1 and 11.5 kcal·mol-1, respectively. The free energy of activation for the epoxidation of ethylene by peroxyformic acid is lowered by about 3 kcal·mol-1 upon complexation with the catalyst.

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