Why don't alkanes oxidize

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Oxidation of a methylene group to a carbonyl group: choice of reaction conditions

If the methylene group is activated by an adjacent group, it is more easily and selectively oxidizable. The figure shows different activating groups, sorted according to decreasing activating influence:

The oxidation to the carboxylic acid can be interrupted by a suitable choice of the oxidizing agent and the reaction conditions. The oxidizing agent must react selectively, since, for example, a carbonyl group is generally oxidized more quickly than a methylene group. Selenium dioxide is particularly suitable as a catalyst for this group of substances. Cobalt or manganese salts are preferred as catalysts for the oxidation of arylalkanes. Since the resulting carbonyl compounds are easier to oxidize than the alkyl radical, the carbonyl compound must be removed from the reaction mixture.

Straight-chain alkanes do not react with common oxidizing agents (e.g. potassium permanganate). Oxidation only occurs with oxygen in the presence of manganese and cobalt salts above 100 or with hot chromium-sulfuric acid. The reaction leads to a product mixture of alcohols, ketones, aldehydes, acids and other oxidation products. C-C cleavage and rearrangements increase the number of by-products. Since the oxidation of saturated hydrocarbons cannot be used for the production of certain compounds, it is not used preparatively.

Example: The oxidation of butane with oxygen over a cobalt acetate catalyst at 165 leads to a product mixture consisting mainly of ethyl methyl ketone, acetic acid and methyl and ethyl acetate in a ratio of 1: 15: 3.