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NEET CHEMISTRYHydrocarbonsEasy

Question

The alkane that gives only one monochloro product on chlorination with Cl2Cl_2 in presence of diffused sunlight is:

A

2,2-Dimethylbutane

B

Neopentane

C

n-Pentane

D

Isopentane

Step-by-Step Solution

  1. Principle of Monochlorination: Free radical chlorination replaces a hydrogen atom with a chlorine atom. The number of isomeric monochloro products formed depends on the number of chemically non-equivalent sets of hydrogen atoms present in the alkane molecule [NCERT 11th, Ch 13, Sec 13.5.2; NCERT 12th, Ch 10, Ex 10.3]. If an alkane has only one type of hydrogen, it yields a single monochloro product.
  2. Analyze Option B (Neopentane / 2,2-Dimethylpropane):
  • Structure: A central quaternary carbon bonded to four methyl groups (C(CH3)4C(CH_3)_4).
  • Symmetry: All 12 hydrogen atoms belong to identical methyl groups attached to the same central atom. They are chemically equivalent.
  • Product: Replacing any one of the 12 hydrogens results in the same compound: 1-chloro-2,2-dimethylpropane.
  1. Analyze Other Options:
  • n-Pentane (CH3CH2CH2CH2CH3CH_3CH_2CH_2CH_2CH_3): Has 3 sets of equivalent hydrogens (C1/C5C_1/C_5, C2/C4C_2/C_4, and C3C_3), yielding 3 isomers.
  • Isopentane (2-Methylbutane): Has 4 different sets of hydrogens, yielding 4 isomers.
  • 2,2-Dimethylbutane: Has 3 different sets of hydrogens, yielding 3 isomers.
  1. Conclusion: Neopentane is the only alkane listed that yields a single monochloro product.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Hydrocarbons. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYHydrocarbonsalkanemonochloroproductchlorinationpresence

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A.Option 1 (Structure missing)
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