22431-90-9Relevant academic research and scientific papers
Kinetics and mechanism of the thermolysis of a five-membered-ring peroxide, 3,3,5,5-tetramethyl-1,2-dioxolane
Richardson, William H.,McGinness, Ronald,O'Neal, H. Edward
, p. 1887 - 1890 (2007/10/02)
The kinetics of the thermolysis of 3,3,5,5-tetramethyl-1,2-dioxolane (1) was studied in benzene solution with a free-radical chain inhibitor (2,6-di-tert-butyl-p-cresol) in the gas phase. The peroxide 1 was susceptible to induced decomposition both in solution without the inhibitor and in the gas phase without conditioned reactor walls. However, under optimum conditions, first-order kinetics were observed in both the gas phase and in solution. Activation parameters for the thermolysis of 1 in benzene solution with the inhibitor at 500 K are Ea = 44.6 ± 0.9 kcal/mol, log A = 15.85 ± 0.42, ΔH≠ = 43.6 ± 0.9 kcal/mol, and ΔS≠ = 11.0 ± 1.9 eu. In the gas phase, the parameters at 500 K are Ea = 45.5 ± 0.3 kcal/mol, log A = 15.72 ± 0.13, ΔH≠ = 44.5 ± 0.3 kcal/mol, and ΔS≠ = 10.4 ± 0.6 eu. These parameters closely approach calculated activation parameters for 1 which are based on a stepwise biradical decomposition mechanism: Ea = 48.6 kcal/mol, log A = 16.55, ΔH≠ = 47.6 kcal/mol, and ΔS≠ = 14.2 eu at 500 K. Considering the susceptibility of 1 to induced decomposition, which will lower the activation parameters, the close approach of the experimental to the calculated parameters indicates that 1 undergoes decomposition by a stepwise biradical route. Thus, there is no mechanistic discontinuity between the stepwise biradical mechanism observed with simply substituted 1,2-dioxetanes (four-membered-ring peroxides) and the five-membered-ring peroxide 1.
Oxymetallation. Part 12. Further Syntheses of Monocyclic Peroxides via Peroxymercuriation
Bloodworth, A. J.,Khan, Jamil A.
, p. 2450 - 2457 (2007/10/02)
The scope of cycloperoxymercuriation as a route to monocyclic peroxides has been investigated by studying the reaction of mercury(II) nitrate with ten representative dienes plus hydrogen peroxide, and with two alkenyl hydroperoxides.By hydrogeno- and bromo-demercuriation of the resultant products, seven new methyl- and bromomethyl-substituted 1,2-dioxacyclo-pentanes and -hexanes have been prepared.The geometrical isomers of three of the 1,2-dioxacyclopentanes (4), (8), and (9) have been separated and assigned cis and trans configurations, and each of the four diastereoisomers of 4-bromo-3-bromomethyl-5-methyl-1,2-dioxacyclopentane (11) has been isolated.Two diastereoisomers of 4-bromo-6-bromomethyl-3-methyl-1,2-dioxacyclohexane (13) are formed and have been separated; their 1H n.m.r. spectra indicate that each has a chair conformation with equatorial methyl and bromomethyl groups, the stereoisomerism arising from the disposition of the bromine substituent.The by-products of peroxymercuriation-reduction have been shown to be unsaturated alcohols whose formation is strongly favoured where the cycloperoxymercurial contains an endocyclic mercurio-substituent.
