Which reagent will you use for the following reaction.
`CH_3CH_2CH_2CH_3 rarrCH_3CH_2CH_2CH_2Cl+CH_3CH_2CHClCH_3`

Options

A. `Cl_2 //` UV light
B. `NaCl+H_2SO_4`
C. `Cl_2` gas in dark
D. `Cl_2` gas in the presence of iron in dark

Answer

A

Explanation

The given reaction is a substitution reaction. It involves the replacement of `1^@` and `2^@` hydrogen of alkanes by chlorine. It occurs in presence of ultraviolet light or at high temperature.
The chlorination does not occur at room temperature in absence of light. In this reaction, light is absorbed by the chlorine molecule and activated chlorine initiates the reaction as follows
Step I `Cl-Cloverset(UV)underset("light")(rarr)2 dotCl`
`dotCl+CH_3-CH_2-CH_2-CH_3 rarr CH_3CH_2CH_2-dotCH_2+HCl`
Step 2 `CH_3-CH_2-CH_2-dotCH_2+Cl_2 rarr CH_3-CH_2-CH_2-CH_2Cl+dotCl`
Step 3 `CH_3-CH_2-CH_2-dotCH_2+dotCl rarr CH_3CH_2CH_2CH_2Cl`