Question

What is radical halogenation?

Answer 1

Halogenation of an alkane leads to the production of a hydrocarbon derivative in which one or more halogen atoms get substituted for hydrogen atoms.
Radical halogenation provides a way through which alkanes can be functionalized.

Complete step by step answer:
Halogenation reaction is a chemical reaction between a halogen and a substance which leads to the substitution of a single hydrogen on the alkane for a single halogen to form a haloalkane.
Alkanes are very unreactive compounds because they are non-polar in nature and they also lack functional groups which are responsible for the reactions to take place.
The reaction for radical halogenation or radical free halogenation proceeds through radical chain mechanisms.
Steps for radical chain mechanism (using chlorination of methane as an example) as follows:
Initiation Step: It breaks the bond between chlorine as it undergoes hemolysis when irradiated with the UV light and this leads to the formation of chlorine radicals.
Propagation Step: In this step, a chlorine radical abstracts a hydrogen on the methane which generates hydrochloric acid and the methyl radical. In the second step of propagation it again generates a chlorine atom. These steps keep on repeating many times until termination takes place.
Termination Step: This step takes place when two chlorine atoms react, or the chlorine atom reacts with a methyl radical to form chloromethane which constitutes a minor pathway through which the product is formed. Here, two methyl radicals sometimes also combine to produce ethane which is a very minor by-product obtained due to this reaction.

Note:
We can control the reaction conditions and also the ratio of chlorine to methane. By doing so, it is possible to favour the formation of one or another chlorinated methane products.