Chemistry - Hydrocarbon Question with Solution | TestHub
Halogenation is a substitution reaction, where halogen replaces one or more hydrogens of hydrocarbon.
Chlorine free radicals form 1°, 2°, and 3° radicals with almost equal ease, whereas bromine free radicals show a clear preference for the formation of tertiary free radicals. Therefore, bromine is less reactive and more selective, while chlorine is more reactive and less selective.
The relative rate of abstraction of hydrogen by Br• is:
3° > 2° > 1°
(1600) (82) (1)
The relative rate of abstraction of hydrogen by Cl• is:
3° > 2° > 1°
(5) (3.8) (1)
1-halo-2,3-dimethyl butane will be obtained in better yields, if halogen is
Options:
Answer:
Solution:
Question Explanation: The question asks which halogen exhibits the highest selectivity toward substitution at a carbon in the given alkane during free radical halogenation.
Concept:
This is based on the relative reactivity–selectivity principle in halogenation reactions.
Solution:
Reactivity order Chlorine (Cl2 ) (approx.):
3° : 2° : 1° ≈ 5 : 3.8 : 1
Reactivity order Bromine (Br2 ) (approx.):
3° : 2° : 1° ≈ 1600 : 82 : 1
If X = Br then
If X = Cl then % of
