617-50-5Relevant articles and documents
Supercritical Carbon Dioxide. 5. Carboxyinversion Reactions of Diacyl Peroxides. Alkyl Group Rearrangement and CO2 Exchange
Sigman, Michael E.,Barbas, John T.,Leffler, John E.
, p. 1754 - 1757 (1987)
The decomposition of bis(isobutyryl) peroxide in supercritical Co2, CCl4, and CHCl3 gives both radical and ion pair-derived products in all three media.The rate constant in supercritical CO2 at 40 deg C, ?* -0.05, and density 0.93 is 3.6 * 10E-5 s-1.The rate constants in CCl4 and in CHCl3 at the same temperature are 7.72 * 10E-5 and 42.5 * 10E-5, respectively.The rate constant in CO2 fits a relationship with ?* observed for aromatic solvents.The products in CO2 include isopropyl isobutyryl carbonate (the carboxyinversion compound), 17percent yield, isopropyl isobutyrate, 5percent or less, and isobutyric acid, 17percent yield.There is no exchange of the inverted CO2 moiety of isopropyl isobutyryl carbonate for CO2 from the medium.The decomposition of cyclobutanecarbonyl m-chlorobenzoyl peroxide in CO2 is compared with the results reported by Taylor et al. (Taylor, K.G.; Govindan, C.K.; Kaelin, M.S.J.Am.Chem.Soc. 1979, 101, 2091) in conventional solvents.The rate constant for the decomposition of this peroxide in CO2 at 55 deg C at a density of 0.81 is 2.2 * 10E-5 s-1, in CCl4 it is 2.93 * 10E-5 s-1, and in CHCl3 it is 27.2 * 10E-5 s-1.The alkyl groups in the alkyl m-chlorobenzoate esters and alkyl m-chlorobenzoyl carbonates (carboxyinversion products) from this peroxide are rearranged in part to cyclopropylmethyl and 3-butenyl groups.The 13C of the carbonate carbonyl in the cyclopropylmethyl m-chlorobenzyl carbonate is about 12percent exchanged, but that from the carboxyinversion product with the unrearranged alkyl group is not exchanged.The effects of medium changes on the product are as follows: the change from CO2 to CCl4 increased the total yield of carboxyinversion compounds, but did not change the relative yields of the isomers appreciably.The further change in medium to CHCl3 drastically lowered the total yield of carboxyinversion compounds, again without changing the ratios of the isomers very much, and at the same time caused a large increase in the total yield of the esters.Both the ester yields and the rate appear to depend more on the hydrogen-bond-donor properties of the medium than on ?*.
Ru-Catalyzed Transfer Hydrogenation of Nitriles, Aromatics, Olefins, Alkynes and Esters
Alshakova, Iryna D.,Gabidullin, Bulat,Nikonov, Georgii I.
, p. 4860 - 4869 (2018/10/02)
This paper reports the preparation of new ruthenium(II) complexes supported by a pyrazole-phosphine ligand and their application to transfer hydrogenation of various substrates. These Ru complexes were found to be efficient catalysts for the reduction of nitriles and olefins. Heterocyclic compounds undergo transfer hydrogenation with good to moderate yields, affording examples of unusual hydrogenation of all-carbon-rings. Internal alkynes with bulky substituents show selective reduction to olefins with the unusual E–selectivity. Esters with strong electron-withdrawing groups can be reduced to the corresponding alcohols, if ethanol is used as the solvent. Possible mechanisms of hydrogenation and olefin isomerization are suggested on the basis of kinetic studies and labelling experiments.
Reactions of alkyl radicals with substituted toluenes and the effect of substituents on dissociation energies of benzyl C-H bonds
Arafat, Abdelfattah M.,Mathew, Samuel K.,Akintobi, Solademi O.,Zavitsas, Andreas A.
, p. 2226 - 2242 (2007/10/03)
Reactions of isopropyl and of undecyl radicals with meta- and para-substituted toluenes are reported. The results demonstrate that the reactivities of toluenes are due to both benzyl-H abstraction and addition of the alkyl radicals to the aromatic ring. Relative reactivities yield curved Hammett plots, consistent with kinetic data reported by Dutsch and Fischer. Abstractions and ring additions occur with comparable rates, but opposite Hammett slopes. Addition is favored by electron-withdrawing and abstraction by electron-donating substituents. The effects of substituents on the dissociation energies of benzyl C-H bonds are shown to be the major factor influencing reaction rates for benzyl-H abstraction by alkyl radicals.
Structure-function correlation in lipase catalysed esterification reactions of short and medium carbon chain length alcohols and acids
Divakar, Soundar
, p. 1919 - 1922 (2007/10/03)
An attempt has been made to correlate the carbon chain lengths of acids and alcohols to the extent of esterification in the Rhizomucor miehei lipase catalyzed esterification reactions involving acids of carbon chain length C2-C5 and alcohols of carbon chain length C1-C8.
