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JEE Main levelOne or more correct optionsDifficulty 2 of 3g3143

Which statements about radical halogenation of alkanes are correct (use $C - H$ (secondary) about 98 kcal/mol, $H - Br$ 88, $H - Cl$ 103)?

A $Br X^{∙}$ is more selective than $Cl X^{∙}$ .
BAbstraction of a secondary H by $Br X^{∙}$ is endothermic.
CAbstraction of a secondary H by $Cl X^{∙}$ is strongly endothermic.
D $Cl X_{2}$ shows a larger 3 degree : 1 degree selectivity than $Br X_{2}$ .

Answer: A, B

For

Br X^{∙}

:

98 - 88 = + 10

kcal/mol (endothermic, late transition state, high selectivity). For

Cl X^{∙}

:

98 - 103 = - 5

kcal/mol (exothermic, early transition state, low selectivity). So statements 1 and 2 are true; 3 is false and 4 is reversed.

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