Which carbon alcohol is more stable

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Oxidation of Alcohols to Aldehydes or Ketones: Mechanism

There are basically two possibilities for the mechanism, namely oxygenation and dehydration.

Oxygenation means the introduction of oxygen, i.e. all H atoms that are bonded to the carbon atom of the OH group (α-hydrogen) are successively oxygenated to hydroxyl groups. According to the Erlenmeyer rule, two OH groups on one carbon atom (hydrates of aldehydes or ketones) are usually not stable, so water is split off:

On the other hand, the hydrate of an aldehyde, which is in equilibrium with aldehyde and water, can be further oxidized to the carboxylic acid. Therefore, if you want to stop the oxidation at the aldehyde stage, you always work under anhydrous conditions.

During dehydrogenation, hydrogen is removed from the alcohol. Primary alcohols are often converted into aldehydes by hydrogen acceptors (e.g. palladium) even in the absence of oxygen.

In the frequently used oxidation with chromic acid or chromates in acidic solution, the alcohol is nucleophilically attached to the Cr (VI) and a chromic acid ester is formed with elimination of water. Presumably in the second step the α-hydrogen of the alcohol is transferred to the chromate residue via a cyclic transition state, whereby the metal assumes the oxidation state + IV:

The chromium (IV) species formed can disproportionate to Cr (III) and Cr (V) or be further reduced, i.e. act as an oxidizing agent. In the end, Cr (VI) is completely reduced to Cr (III).