Question

Halogenation is a substitution reaction, where halogen replaces one or more hydrogens of hydrocarbon.
Chlorine free radical make $1^{\circ },2^{\circ },3^{\circ }$ radicals with almost equal ease, whereas bromine free radicals have a clear preference for the formation of tertiary free radicals. So ,bromine is less reactive, and more selective whereas chlorine is less selective
and more effective.
The relative rate of abstraction of hydrogen by Br is
$\underset{\left(1600\right)}{3^{\circ }}>\underset{\left(82\right)}{2^{\circ }}>\underset{\left(1\right)}{1^{\circ }}$
The relative rate of abstraction of hydrogen by Cl is
$\underset{\left(5\right)}{3^{\circ }}>\underset{\left(3.8\right)}{2^{\circ }}>\underset{\left(1\right)}{1^{\circ }}$
D.Which of the following will give five monochloro products, when allowed to react with $C{l}_2$ in presence of sun light (excluding stereoisomers) ?

• A. n - pentane
• B. Iso - pentane
• C. 2 - methyl - pentane
• D. 3 - methyl - pentane

Answer 1

Answer: (C)

2 - methyl - pentane

To form five monochloro products refer the above image-

n-pentane has only three as refer to IMAGE $01$

Iso-pentane has only four as refer to IMAGE $02$ and

$2-$Methyl-pentane has five products as refer to the IMAGE $03$