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When alcohols are treated with acidic hexavalent chromium, it removes all the alpha hydrogen atoms from alcohol.

This is because chromium is a strong oxidizing agent.

Therefore, the primary alcohols are converted to acids. Secondary alcohols are converted to ketones and there is no reaction for tertiary alcohols.

Cyclohexanols react with chromic acid to form cyclohexanone.

The reaction involves 2 steps:

The first step is the nucleophilic attack of alcohol on metal followed by the rearrangement to form chromate ester. In the second step, chromate ester undergoes hydrolysis to form cyclohexanone.

Hindered alcohols are generally more reactive towards chromium oxidation than unhindered alcohols.

In the given cyclohexanols, the tertiary butyl group is the heavier group, therefore it remains in the equatorial position.

The stable chair confirmations of the given cyclohexanols can be given as:

Cyclohexanol having a hydroxyl group in the axial position will react faster because the hydroxyl group will be more hindered. Therefore, cyclohexanol A will react faster with chromium.