Identify the structure of the final product (D) in the following sequence of the reactions:

Total number of sp^2$sp^2$ hybridised carbon atoms in product D is dots$\dots$.

### Related Formula textTerminal Alkyne (textR-CequivtextCH) xrightarrow[2.\,textH_2textO_2 / textOH^-]1.\,textB_2textH_6 textR-CH_2text-CHO quad text(Anti-Markovnikov Hydroboration-Oxidation)$$\text{Terminal Alkyne } (\text{R-C}\equiv\text{CH}) \xrightarrow[2.\,\text{H}_2\text{O}_2 / \text{OH}^-]{1.\,\text{B}_2\text{H}_6} \text{R-CH}_2\text{-CHO} \quad \text{(Anti-Markovnikov Hydroboration-Oxidation)}$$ ### Core Logic Let's track the molecular changes at every intermediate junction: - Step 1: Acetophenone (textPh-CO-CH_3$\text{Ph-CO-CH}_3$) reacts with textPCl_5$\text{PCl}_5$ to generate a gem-dichloride intermediate [A]: textPh-CCl_2text-CH_3$\text{Ph-CCl}_2\text{-CH}_3$. - Step 2: Reaction with 3$3$ equivalents of the incredibly strong base textNaNH_2$\text{NaNH}_2$ triggers dual elimination to form a terminal sodium acetylide salt [B]: textPh-CequivtextC^-textNa^+$\text{Ph-C}\equiv\text{C}^-\text{Na}^+$. - Step 3: Acidification yields phenylacetylene [C]: textPh-CequivtextCH$\text{Ph-C}\equiv\text{CH}$. - Step 4: Hydroboration-oxidation of phenylacetylene leads to anti-Markovnikov water addition forming an enol structure, which immediately tautomerizes to [D] phenylacetaldehyde: textPh-CH_2text-CHO$\text{Ph-CH}_2\text{-CHO}$. ### Step 1: Counting Hybridized Carbons The step transformations match the sequential tracking map:

Let's locate all sp^2$sp^2$ hybridised carbon environments in product D (textPh-CH_2text-CHO$\text{Ph-CH}_2\text{-CHO}$): 1. The aromatic benzene ring contains 6 sp^2$sp^2$ carbon atoms. 2. The aldehyde carbonyl carbon (-textCHO$-\text{CHO}$) is double-bonded to oxygen, adding 1 sp^2$sp^2$ carbon atom. 3. The aliphatic link carbon (-textCH_2-$-\text{CH}_2-$) is entirely sp^3$sp^3$ hybridized. Total sp^2$sp^2$ carbon count = 6 + 1 = 7$= 6 + 1 = 7$. ### Pattern Recognition Alkyne oxidation mapping: Hydroboration-oxidation transforms a terminal alkyne into an aldehyde carbonyl group, while oxymercuration-demercuration yields a ketone carbonyl. Both introduce precisely one extra carbonyl sp^2$sp^2$ site on top of the original aromatic framework. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids Class 11 Chemistry: Hydrocarbons