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Question

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Answer

The final product is Cyclohexane-1,2-dione.

Explanation

Solution

The reaction proceeds in two main steps:

Step 1: Nitrosation of Cyclohexanone

  1. Generation of Nitrous Acid: Sodium nitrite (NaNO2\text{NaNO}_2) reacts with hydrochloric acid (HCl\text{HCl}) to generate nitrous acid (HNO2\text{HNO}_2). NaNO2+HClHNO2+NaCl\text{NaNO}_2 + \text{HCl} \rightarrow \text{HNO}_2 + \text{NaCl}

  2. Formation of Nitrosonium Ion: Nitrous acid is protonated and then loses water to form the nitrosonium ion (NO+\text{NO}^+), which is a strong electrophile. HNO2+H+H2O+N=OH2O+NO+\text{HNO}_2 + \text{H}^+ \rightleftharpoons \text{H}_2\text{O}^+-\text{N}=\text{O} \rightleftharpoons \text{H}_2\text{O} + \text{NO}^+

  3. Enolization of Ketone: Cyclohexanone, being a ketone with alpha-hydrogens, exists in equilibrium with its enol form.

  4. Electrophilic Attack: The nucleophilic alpha-carbon of the enol form attacks the electrophilic nitrosonium ion (NO+\text{NO}^+), forming an alpha-nitroso ketone.

  5. Tautomerization: The alpha-nitroso ketone is generally unstable and rapidly tautomerizes to the more stable alpha-oxime ketone (2-(hydroxyimino)cyclohexan-1-one).

Step 2: Hydrolysis of the Oxime

  1. Acid-catalyzed Hydrolysis: The alpha-oxime ketone (2-(hydroxyimino)cyclohexan-1-one) is subjected to acidic hydrolysis (H3O+\text{H}_3\text{O}^+). Under these conditions, the oxime group (=NOH=\text{NOH}) is hydrolyzed to a carbonyl group (=O=\text{O}), similar to the hydrolysis of an imine. This reaction releases hydroxylamine (NH2OH\text{NH}_2\text{OH}).

The final product is cyclohexane-1,2-dione.