Alkylaromatic hydrocarbon autoxidation

Autoxidation of alkylaromatic hydrocarbons has been studied exten-- sively in recent years (1, 2, 3,11,12 13), and the mechanism (Reactions 1-4) is now well understood. 

In general, liquid phase autoxidations on hydrocarbons after the initial stages take place, may be considered as co-oxidations with aldehydes, alcohols, ketones, carboxylic acids, etc. Often aldehydes or ketones are deliberately added to hydrocarbon autoxidations in order to promote the reaction. For example, in the cobalt-catalyzed oxidations of alkylaromatics (see Section II.B.3.b), aldehydes, or methyl ethyl ketone are usually added in commercial processes in order to attain high rates and eliminate induction periods. 

The determination of peroxides has two goals one is to monitor peroxide concentration used as initiator and catalysts and the other is to detect formation of hazardous peroxides formed as autoxidation products in ethers, acetals, dienes, and alkylaromatic hydrocarbons. A sample is dissolved in a mixture of acetic acid and chloroform. The solution is deaerated and potassium iodide reagent is added and let to react for 1 h in darkness. The iodine formed in reaction is measured by absorbance at 470 nm and result calculated to active oxygen in the sample. The method can determine hydroperoxides, peroxides, peresters, and ketone peroxides. Oxidizing and reducing agents interfere with flic determination. 

A complete mechanism for the autoxidation of alkylaromatic hydrocarbons by cobalt(n) in acetic acid has not been established,25 6 although a complex rate law has been determined for tetralin. 22 The reaction most likely proceeds by a fiiee radical chain mechanism in which the purpose of the cobalt ions is to provide a hi h steady state concentration of free radicals by catalysis of the decomposition of THP. The free radical nature of the autoxidation of tettalin with the colloidal CoPy catalysts is supported by experiments which showed inhibition of the reaction by 2,6-di-rerr-butylphenol and 2,6-di-rm-butyl-4-methylphenol, and by a shortening of the induction period and increase of the reaction rate when azobis(isobut nitrile) was added to the reaction mixture as a free radical initiator. 

The determination of peroxides has two goals one is to monitor peroxide concentration used as initiator and catalysts and flic other is to detect formation of hazardous peroxides formed as autoxidation products in ethers, acetals, dienes, and alkylaromatic hydrocarbons. A sample is dissolved in a mixture of acetic acid and chloroform. The solu-... 

In some cases metalloporphyrins have been found to catalyze the autoxidation of alkanes or the alkyl groups of other saturated hydrocarbons (alkylaromatics, cycloalkanes, etc.) [85]. Typically,... 

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