The ability of microemulsions to dissolve polar and non-polar components with a huge internal interface can overcome the reagent incompatibilities frequently encountered in organic reactions. We investigated model epoxidation reactions of α,β-unsaturated enones and alkaline hydrogen peroxide in different nonionic microemulsions, both in the presence and absence of a phase-transfer agent (PTA). The obtained reaction profiles were compared with those for the corresponding surfactant-free two-phase systems. In addition, we defined a time constant τ as a measure for the rate of turnover. The epoxidation of trans-chalcone using an n-alkyl-polyoxyethylene surfactant based microemulsion was fastest in the system with the PTA (τ=66 min) and slightly slower without the PTA (τ=77 min). It was still slower in the two-phase system with a PTA (τ=114 min) and extremely sluggish without a phase-transfer agent. With n-alkyl β-D-glucopyranoside as the surfactant the conversion was twice as fast than in the former microemulsion systems, but the PTA did not accelerate the reaction further (τ=35 and 33 min). The epoxidation of vitamin K3, the second model system, was extremely accelerated. It proceeded a factor of approximately 35 faster in the microemulsion (τ=1.44 min) than in the corresponding two-phase system (τ=57 min).
%0 Journal Article
%1 doi:10.1002/chem.200600550
%A Wielpütz, Thomas
%A Sottmann, Thomas
%A Strey, Reinhard
%A Schmidt, Friederike
%A Berkessel, Albrecht
%D 2006
%J Chemistry – A European Journal
%K Sottmann
%N 29
%P 7565-7575
%R 10.1002/chem.200600550
%T Dramatic Enhancement of Enone Epoxidation Rates in Nonionic Microemulsions
%U https://onlinelibrary.wiley.com/doi/abs/10.1002/chem.200600550
%V 12
%X The ability of microemulsions to dissolve polar and non-polar components with a huge internal interface can overcome the reagent incompatibilities frequently encountered in organic reactions. We investigated model epoxidation reactions of α,β-unsaturated enones and alkaline hydrogen peroxide in different nonionic microemulsions, both in the presence and absence of a phase-transfer agent (PTA). The obtained reaction profiles were compared with those for the corresponding surfactant-free two-phase systems. In addition, we defined a time constant τ as a measure for the rate of turnover. The epoxidation of trans-chalcone using an n-alkyl-polyoxyethylene surfactant based microemulsion was fastest in the system with the PTA (τ=66 min) and slightly slower without the PTA (τ=77 min). It was still slower in the two-phase system with a PTA (τ=114 min) and extremely sluggish without a phase-transfer agent. With n-alkyl β-D-glucopyranoside as the surfactant the conversion was twice as fast than in the former microemulsion systems, but the PTA did not accelerate the reaction further (τ=35 and 33 min). The epoxidation of vitamin K3, the second model system, was extremely accelerated. It proceeded a factor of approximately 35 faster in the microemulsion (τ=1.44 min) than in the corresponding two-phase system (τ=57 min).
@article{doi:10.1002/chem.200600550,
abstract = {The ability of microemulsions to dissolve polar and non-polar components with a huge internal interface can overcome the reagent incompatibilities frequently encountered in organic reactions. We investigated model epoxidation reactions of α,β-unsaturated enones and alkaline hydrogen peroxide in different nonionic microemulsions, both in the presence and absence of a phase-transfer agent (PTA). The obtained reaction profiles were compared with those for the corresponding surfactant-free two-phase systems. In addition, we defined a time constant τ as a measure for the rate of turnover. The epoxidation of trans-chalcone using an n-alkyl-polyoxyethylene surfactant based microemulsion was fastest in the system with the PTA (τ=66 min) and slightly slower without the PTA (τ=77 min). It was still slower in the two-phase system with a PTA (τ=114 min) and extremely sluggish without a phase-transfer agent. With n-alkyl β-D-glucopyranoside as the surfactant the conversion was twice as fast than in the former microemulsion systems, but the PTA did not accelerate the reaction further (τ=35 and 33 min). The epoxidation of vitamin K3, the second model system, was extremely accelerated. It proceeded a factor of approximately 35 faster in the microemulsion (τ=1.44 min) than in the corresponding two-phase system (τ=57 min).},
added-at = {2021-10-26T08:32:58.000+0200},
author = {Wielpütz, Thomas and Sottmann, Thomas and Strey, Reinhard and Schmidt, Friederike and Berkessel, Albrecht},
biburl = {https://www.bibsonomy.org/bibtex/23d5efbb91db285d5723f53e7c65d17ec/mho},
doi = {10.1002/chem.200600550},
eprint = {https://onlinelibrary.wiley.com/doi/pdf/10.1002/chem.200600550},
interhash = {76350d5d60c15c5df51cf934aae8ab46},
intrahash = {3d5efbb91db285d5723f53e7c65d17ec},
journal = {Chemistry – A European Journal},
keywords = {Sottmann},
number = 29,
pages = {7565-7575},
timestamp = {2021-10-26T08:32:58.000+0200},
title = {Dramatic Enhancement of Enone Epoxidation Rates in Nonionic Microemulsions},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/chem.200600550},
volume = 12,
year = 2006
}