Formation of halogen alkanes

The formation of halogenalkanes:

• When a mixture of an alkane and halogen are put into a bright light, they will react and form a halogenalkane
• They do not react in the dark
• An example is the reaction of hexane and bromine under a bright light forming misty fumes of hydrogen bromide and the solution turns colourless

Example: CH4 + Cl2---> CH3Cl + HCl

Initiation:

• The Cl-Cl bond is broken by a single quantum of UV light , as the energy is greater than the Cl-Cl bond
• Since the atoms are both the same, the Cl-Cl bond breaks and an electron goes to each chlorine atom, this is called "homolytic"
• This produces 2 free radicals, which are highly reactive 
• The C-H bond doesn't break because it requires more energy than a single quantum of UV…