See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Concept: SeO2 (selenium dioxide) is a well-known oxidizing agent used in the Riley oxidation. Its key characteristic reactivity with carbonyl compounds (ketones) is alpha-oxidation — it selectively oxidizes the carbon alpha to a carbonyl group. Step 1: Identify the substrate. Cyclohexanone has a carbonyl group at C1 and alpha carbons at C2 and C6. Step 2: Understand SeO2 mechanism. SeO2 oxidizes the alpha carbon of a ketone. The mechanism involves an ene-type reaction where SeO2 reacts at the alpha C-H bond adjacent to the carbonyl, ultimately introducing an oxygen function at the alpha position. Step 3: Determine the product. When SeO2 oxidizes cyclohexanone, it introduces a carbonyl (C=O) at the alpha carbon (C2), converting the alpha CH2 into C=O. This gives cyclohexane-1,2-dione (a 1,2-diketone). Step 4: Evaluate other options. - Option (a): 2-hydroxycyclohexan-1-one — this would be an alpha-hydroxy ketone, which can be an intermediate but SeO2 oxidation of a ketone typically proceeds to the alpha-diketone product under standard conditions. - Option (c): 2-cyclohexen-1-one — this is an alpha,beta-unsaturated ketone, which would require dehydrogenation, not the typical SeO2 alpha-oxidation product of a saturated ketone. - Option (d): cyclopentane-1,2-dione — this would require ring contraction, which does not occur under SeO2 oxidation conditions. Step 5: Conclusion. SeO2 oxidation of cyclohexanone gives cyclohexane-1,2-dione by alpha-oxidation at C2. Therefore, the correct answer is B.