Inhibition of the chain reaction of oxidation of cyclohexanol by molecular iodine, potassium iodide and bromide

Aleksandrov, A. L.; Sapacheva, T. I.; Denisov, Ye.T.

doi:10.1016/0031-6458(70)90082-1

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“…The data of these experiments (table) clearly show the simultaneous retardation of the SE heterolysis (the overall consumption of SE) and oxida tion with an increase in [TMAC]. This is the unex pected result, because in the study of the retardation of BS (TSA+SE) oxidation by the iodide and bromide ions [3], we did not propose the strong effect of the radical chain inhibitors I -and Br - [5] on the SE heterolysis, the rate of which in the BS (TSA+SE) is by 20-25 times higher than [1]. The results of the experiments with LiCl carried out similarly to the experiments with TMAC (table) by the method "one experiment-three rates" are given in Figs.…”

Section: Resultsmentioning

confidence: 63%

“…(1) The retardation of the SE oxidation by the Clanion by the mechanism with the electron abstraction from Cl -by the oxygen containing radical, as was proposed for the oxidation of the secondary alcohol in the presence of I -and Br - [5], is improbable, because Cl -inhibits also the heterolytic reaction. (2) The simultaneous retardation of the heterolysis and the quasi radical stage (the SE oxidation), i.e., the rigid link between the heterolysis and oxidation corre sponds to the conversion scheme suggested earlier [2]: protolysis of SE → carbocation formation → carbene formation → oxygen uptake.…”

Section: Resultsmentioning

confidence: 97%

“…Our recent work on the retardation by potas sium iodide and bromide of the oxidation of SE with oxygen in acidified polar solvents [3] posed new ques tions without clarification of the principal problem about the mechanism of the mild oxidation of SE, which is hardly oxidized via the traditional route with the participation of a peroxy radical [4]. Moreover, the similarity of the retardation of the mild oxidation of SE and the radical chain oxidation of secondary alco hols shown in [3] allows the possibility of interpreta tion of the SE oxidation via the secondary oxyperoxide radical [5], i.e., by the mechanism alternative to the intermediate formation of a carbene [2]. In this study, we present the results of the examination of the retar dation of the SE oxidation in the acidic alcohol medium by halide salts, mainly by the salts of HCl.…”

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confidence: 96%

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Inhibition of mild oxidation of styrene epoxide by oxygen in acidic alcohol solution by halide ions

Petrov

Solyanikov

2012

Pet. Chem.

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327p Toluenesulfonic (TSA) and perchloric (HClO 4 , PCA) acids catalyze the fast consumption of styrene epoxide (SE) in a tert butanol-chlorobenzene (9 : 1, v/v, BUC) solution [1,2], with the oxidation of SE being 5% of the total consumption in an oxygen atmo sphere. Our recent work on the retardation by potas sium iodide and bromide of the oxidation of SE with oxygen in acidified polar solvents [3] posed new ques tions without clarification of the principal problem about the mechanism of the mild oxidation of SE, which is hardly oxidized via the traditional route with the participation of a peroxy radical [4]. Moreover, the similarity of the retardation of the mild oxidation of SE and the radical chain oxidation of secondary alco hols shown in [3] allows the possibility of interpreta tion of the SE oxidation via the secondary oxyperoxide radical [5], i.e., by the mechanism alternative to the intermediate formation of a carbene [2]. In this study, we present the results of the examination of the retar dation of the SE oxidation in the acidic alcohol medium by halide salts, mainly by the salts of HCl. The retardation is unexpected, because there are no data about the ability of chlorides to inhibit the oxida tion in the extensive literature on the radical chain oxidation of hydrocarbons. Under our conditions, the salts of HCl inhibit both SE oxidation and consump tion, the heterolytic process, with a rate being 20-25 fold higher than the oxidation rate. The interrelation of the heterolysis and the oxidation manifesting itself in the simultaneous retardation of the two processes is within the concept of the SE oxidation according to the mechanism [2]. EXPERIMENTAL Experiments were carried out in a mixed solvent tert butanol-chlorobenzene (9 : 1, v/v, BUC). The solvent components were purified according to stan dard procedures before mixing. Lithium chloride (chemically pure) and tetrabuthylammonium iodide (TBAI, pure) were used without purification. Benzyl triethylammonium chloride (BTEAC, pure) and tet ramethylammonium chloride (TMAC) were recrys tallized twice before use. BTEAC was recrystallized from a mixture of acetone-acetonitrile (1 : 1, v/v). TMAC was recrystallized from a mixture of ethanolisopropanol (1 : 1, v/v). The rates of oxygen uptake were measured in a simple rather than in a two com partment reactor, as had been done in our previous studies. SE and the acid were mixed in a BUC solution in the quartz reactor of a volumetric setup. The solu tions were frozen by liquid nitrogen, the air was evac uated, and the reactor and the setup were filled with oxygen. The reactor was loaded into a thermostat, and the oxygen uptake was measured after heating. The oxidation solutions obtained in the experiments in the presence of TMAC and LiCl were analyzed by liquid chromatography for residual SE and formed benzal dehyde (BA). The rates of the SE consumption V SE = (Δ[SE]/t) and of the BA formation V BA = (Δ[BA]/t), where t is the time of the experiment, were calculated from these data. Three values of the rates ...

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Section: Resultsmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 97%