Question

Explain mechanism of free radical halogenation of alkanes

Answer 1

When treated with Br2 or Cl2, radical substitution of R-H generates the alkyl halide and HX.
Alkane R-H relative reactivity order : tertiary > secondary > primary > methyl.
Halogen reactivity F2 > Cl2 > Br2 > I2Only chlorination and bromination are useful in the laboratory.
Bromination is selective for the R-H that gives the most stable radical.
Chlorination is less selectiveReaction proceeds via an radical chain mechanism which involves radical intermediates.
The termination steps are of low probability due to the low concentration of the radical species meaning that the chances of them colliding is very low.