QNEET-2024-Ch-7: NEET 2024 Chemistry - Class 12 NEET-2024-Ch-7 Solution: Identify the correct reagents that would bring about the…

Explanation:

1. Hydroboration-Oxidation (Anti-Markovnikov Hydration):
2. Treatment of the terminal alkene with $\text{BH}_3$ followed by $\text{H}_2\text{O}_2/\text{OH}^-$ adds $-\text{H}$ and $-\text{OH}$ across the double bond in an anti-Markovnikov fashion (syn-addition):
3. $$\text{R}-\text{CH}=\text{CH}_2 \xrightarrow{\text{(i) } \text{BH}_3,\; \text{(ii) } \text{H}_2\text{O}_2/\text{OH}^-} \text{R}-\text{CH}_2-\text{CH}_2\text{OH}\quad (1^\circ \text{ alcohol})$$
4. Selective Oxidation to Aldehyde:
5. Oxidation of this primary alcohol using Pyridinium chlorochromate ($\text{PCC}$) selectively stops at the aldehyde stage without over-oxidizing to a carboxylic acid:
6. $$\text{R}-\text{CH}_2-\text{CH}_2\text{OH} \xrightarrow{\text{PCC}} \text{R}-\text{CH}_2-\text{CHO}$$

Why the other pathways fail:

1. Acid-catalyzed hydration ($\text{H}_2\text{O}/\text{H}^+$) follows Markovnikov's rule (forming a $2^\circ$ carbocation/alcohol), which on oxidation gives a ketone rather than an aldehyde.
2. Alkaline $\text{KMnO}_4$ is a strong oxidizing agent that would oxidize a primary alcohol directly to a carboxylic acid ($-\text{COOH}$) instead of stopping at an aldehyde ($-\text{CHO}$).