QNEET-2024-Ch-2: NEET 2024 Chemistry - Class 11 NEET-2024-Ch-2 Solution: A compound with a molecular formula of \(C_6H_{14}\) has two…

Core Concept & Governing Principle - A tertiary carbon (3° C) is a carbon atom bonded to three other carbon atoms. - For a given molecular formula, the number of possible isomers can be determined by constructing all distinct carbon skeletons and counting the tertiary carbons in each. Step 1: Determine the degree of unsaturation. For $C_6H_{14}$, the formula for a saturated acyclic hydrocarbon (alkane) is $C_nH_{2n+2}$. Substituting $n=6$ gives $C_6H_{14}$, confirming the compound is a saturated acyclic alkane (no rings or multiple bonds). Step 2: List all possible acyclic isomers of $C_6H_{14}$. The six constitutional isomers are: 1. n‑hexane 2. 2‑methylpentane 3. 3‑methylpentane 4. 2,2‑dimethylbutane 5. 2,3‑dimethylbutane 6. 2,4‑dimethylpentane (identical to 2‑methylpentane by symmetry, so not a separate isomer). Step 3: Identify the number of tertiary carbons in each isomer. - **n‑hexane**: linear chain; all internal carbons are secondary (2°). → 0 tertiary carbons. - **2‑methylpentane**: carbon‑2 is attached to three carbons (C‑1, C‑3, and the methyl substituent) → 1 tertiary carbon. → 1 tertiary carbon. - **3‑methylpentane**: carbon‑3 is attached to three carbons (C‑2, C‑4, and the methyl substituent) → 1 tertiary carbon. → 1 tertiary carbon. - **2,2‑dimethylbutane**: the central carbon (C‑2) is attached to three carbons (C‑1, C‑3, and two methyl groups) → 1 tertiary carbon. → 1 tertiary carbon. - **2,3‑dimethylbutane**: carbon‑2 is attached to three carbons (C‑1, C‑3, and a methyl group) and carbon‑3 is similarly attached to three carbons (C‑2, C‑4, and a methyl group). → 2 tertiary carbons. Step 4: Select the isomer that contains exactly two tertiary carbons.

Only **2,3‑dimethylbutane** satisfies the condition of having two tertiary carbons. Final Conclusion & Correct Option The IUPAC name of the $C_6H_{14}$ compound with two tertiary carbons is **2,3‑dimethylbutane**. **Correct option: C) 2,3-dimethylbutane**.