3- Butene-2-hydroperoxide, decomposition

T. Traylor In benzene solution, were products of butene hydroperoxide decomposition the same at very high and very low concentrations ... 

The experimental activation energies given in the last column of Table II are in the anticipated order of magnitudes. The activation energy of 24.0 kcal. per mole for the oxidation of 1-hexadecene to hydroperoxide is close to the value of 25.3 kcal. per mole recently reported for the constant velocity of peroxide accumulation. .. for butene-1 (9). The activation energy for the alkenyl hydroperoxide decomposition is reasonable. The activation energy of 48.1 kcal. per mole for the decomposition polymeric dialkyl peroxide is considerably higher than the value of about 37 kcal. per mole for tert-butyl peroxide decomposition. The... 

The observed half life at 100°C. of 23 hours for a dilute solution of hydroperoxide in benzene indicates that significant decomposition may occur in the autoxidation of butene, depending on reaction conditions. No reliable evaluation can be made because of the known complications introduced on hydroperoxide decomposition by the effect of the solvent, the hydroperoxide concentration (2), the presence of oxygen (12), and the possibility of a strong acceleration in rate in the presence of oxidizing olefin, observed in at least one system (8). However, using the data reported by Bateman for a benzene solvent at 100 °C. in the presence of air (2), l-butene-3-hydroperoxide decomposes 13 times faster than cyclohexene hydroperoxide, a product which may be formed in extremely high yield by the oxidation of cyclohexene. 

The use of cobalt and manganese carboxylates to initiate the oxidation of a large number of olefins such as the butenes [447, 448], propylene [449], oleic [450] linoleic [451], and stearic [452, 453] acids or their derivatives and a-methylstyrene [454, 455] is well known. The kinetics of oxidation of a-methylstyrene in the presence of cobaltous and manganous acetylacetonates as well as copper phthalocy-anine have been investigated [454, 455]. The results of this study led Kamiya to postulate a mechanism involving formation of radical species by a metal dioxygen complex, equation (270), concurrent with radical generation by hydroperoxide decomposition. 

Butenes were subjected to photosensitized reaction with molecular oxygen in methanol. 1-Butene proved unreactive. A single hydroperoxide, l-butene-3-hydroperoxide, was produced from 2-butene and isolated by preparative gas chromatography, Thermal and catalyzed decomposition of pure hydroperoxide in benzene and other solvents did not result in formation of any acetaldehyde or propionaldehyde. The absence of these aldehydes suggests that they arise by an addition mechanism in the autoxidation of butenes where they are important products. l-Butene-3-hydroperoxide in the absence of catalyst is converted predominantly to methyl vinyl ketone and a smaller quantity of methyl vinyl carbinol —volatile products usually not detected in important quantities in the autoxidation of butene. 

Neither the thermal nor the cobalt-catalyzed decomposition of 3-butene-2-hydroperoxide in benzene at 100 °C. produced any acetaldehyde or propionaldehyde. In the presence of a trace of sulfuric acid, a small amount of acetaldehyde along with a large number of other products were produced on mixing. Furthermore, on heating at 100°C., polymerization is apparently the major reaction no volatile products were detected, and only a slight increase in acetaldehyde was observed. Pyrolysis of a benzene or carbon tetrachloride solution at 200°C. in the injection block of the gas chromatograph gave no acetaldehyde or propionaldehyde, and none was detected in any experiments conducted in methanol. 

Decomposition of a 0.07M solution of 2-butene-3-hydroperoxide in benzene at 100°C. had a half-life of 23 hours. The final products were 37% methyl vinyl ketone, 37% methyl vinyl carbinol, and 26% acetone. Attempts to substantiate the identity of the acetone were unsuccessful, but it was the only anticipated product with the correct gas chromatographic retention time on four different absorbents. 

Table I. Catalyzed Decomposition of 1-Butene-3-hydroperoxide in Benzene0...

In oxidation studies it has usually been assumed that thermal decomposition of alkyl hydroperoxides leads to the formation of alcohols. However, carbonyl-forming eliminations of hydroperoxides, usually under the influence of base, are well known. Of more interest, nucleophlic rearrangements, generally acid-catalyzed, have been shown to produce a mixture of carbonyl and alcohol products by fission of the molecule (6). For l-butene-3-hydroperoxide it might have been expected that a rearrangement (Reaction 1) similar to that which occurs with cumene hydroperoxide could produce two molecules of acetaldehyde. 

Fig. 15.47. Solvent dependence of the decomposition of the symmetric primary ozonide formed in the ozonolysis of tetramethylethene (2,3-di-methyl-2-butene). The initially formed carbonyl oxide forms a hydroperoxide in methanol, while it dimerizes to give a 1,2,4,5-tetroxane in CH2C12.

Alkene Oxidation Reactions. The reaction of triethylsilane with ozone and use of the intermediate triethylsilyl hydrotrioxide in oxidation reactions have been described. Initial oxidation reactions reported included the formation of the 9,10-endoperoxide from 9,10-dimethylanthracene (eq 1), and an allyUc hydroperoxide from 2,3-dimethyl-2-butene (eq 2). Researchers also observed a near-IR emission from triethylsilyl hydrotrioxide as it decomposed at —60°C, consistent with generation of singlet oxygen. Other workers have characterized triethylsilyl hydrotrioxide by NMR spectroscopy and and measured the kinetics of its decomposition in deuterated acetone. ... 

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