Question 3

1. In reaction 1, 3-phenylpropanoic acid undergoes the Hell-Volhard-Zelinsky (HVZ) reaction to produce 2-bromo-3-phenylpropanoic acid ($P$). The unsaturated carbons include the 6 carbons of the benzene ring and the 1 carbon of the carboxylic acid carbonyl, totaling 7.

2. In reaction 2, Benzaldehyde and Formaldehyde undergo a Cross-Cannizzaro reaction in the presence of $NaOH$. Formaldehyde is oxidized to sodium formate, and benzaldehyde is reduced to benzyl alcohol ($Q$). The number of unsaturated carbons in the monocyclic product $Q$ (benzyl alcohol) is 6 (from the benzene ring).

3. In reaction 3, ethynylbenzene (phenylacetylene) reacts with $NaNH_2$ to form an acetylide ion, which then reacts with allyl bromide to yield 1-phenylpent-4-en-1-yne. Subsequent hydration with $Hg^{2+}/H_3O^+$ (Markovnikov addition) yields 1-phenylpent-4-en-1-one ($R$). The number of unsaturated carbons is 6 (benzene ring) + 1 (ketone carbonyl) + 2 (terminal alkene) = 9.

4. In reaction 4, Indene undergoes reductive ozonolysis to form 2-(2-oxoethyl)benzaldehyde. This dialdehyde/keto-aldehyde reacts with 2 equivalents of $CH_3MgBr$ to form a diol. Subsequent acid-catalyzed dehydration ($H^+, \Delta$) produces a product ($S$) with two external double bonds conjugated with the benzene ring (e.g., 1-(prop-1-en-1-yl)-2-vinylbenzene). The number of unsaturated carbons is 6 (benzene ring) + 2 (from first alkene side chain) + 2 (from second alkene side chain) = 10.

Comparing all products, $S$ contains the highest number of unsaturated carbon atoms (10).