Consider the following reaction of benzene.

In compound (Q), the percentage of oxygen is ___ %. (Nearest integer)

We need to determine the mass percentage of oxygen in compound (Q) obtained from the given reaction sequence starting with benzene.

1. Reaction Analysis:

• Step 1: Friedel-Crafts Acylation (Formation of P)
  Benzene reacts with the acyl chloride end of the bifunctional reagent in the presence of anhydrous $$\text{AlCl}_3$$. The chlorine atom acts as a leaving group, forming an acylium ion intermediate that attacks the benzene ring.
  $$\text{P} = \text{1-phenylbutane-1,3-dione}$$ (as shown in the reaction scheme: a benzene ring substituted with a $$-\text{CO}-\text{CH}_2-\text{CO}-\text{CH}_3$$ chain).
• Step 2: Intramolecular Aldol Condensation (Formation of Q)
  Treating the 1,3-dione (P) with aqueous $$\text{NaOH}$$ and heat ($$\Delta$$) drives an intramolecular aldol condensation. The base abstracts an acidic alpha-proton from the terminal methyl group ($$-\text{CO}-\text{CH}_3$$) to form a nucleophilic enolate ion. This ion attacks the benzylic carbonyl carbon to form a stable 5-membered ring. Subsequent dehydration ($$-\text{H}_2\text{O}$$) yields the final cyclic $$\alpha,\beta$$-unsaturated ketone product (Q) displayed in the diagram.
  $$\text{Q} = \text{3-phenylcyclopent-2-en-1-one}$$

2. Mass Percentage of Oxygen:

$$\text{Percentage of Oxygen} = \left( \frac{\text{Mass of Oxygen}}{\text{Total Molar Mass of Q}} \right) \times 100$$

$$\text{Percentage of Oxygen} = \left( \frac{16}{158} \right) \times 100 \approx 10\%$$

Answer: 10