Solved: CHEMISTRY Question for NEET

NEET CHEMISTRYEasy

The alkane that gives only one monochloro product on chlorination with $Cl_2$ in presence of diffused sunlight is:

2,2-Dimethylbutane

Neopentane

n-Pentane

Isopentane

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.
Analyze Option B (Neopentane / 2,2-Dimethylpropane):

Structure: A central quaternary carbon bonded to four methyl groups ( $C(CH_3)_4$ ).
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.

n-Pentane ( $CH_3CH_2CH_2CH_2CH_3$ ): Has 3 sets of equivalent hydrogens ( $C_1/C_5$ , $C_2/C_4$ , and $C_3$ ), 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.

Conclusion: Neopentane is the only alkane listed that yields a single monochloro product.

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