Question

1)why halogenations are more intrinsically selective for more subtituted carbon?

2)why more substitued radicals are more stale?

3)why brominations are more selective than chlorination?

Answer 1

1) tertiary radicals are more stable than secondary radicals. Secondary radicals are more stable than primary radicals. Therefore halogenation are more intrinsically selective for more substituted carbon.

2. More substituted radicals are more stable because more substituted radicals will form more hyperconjugation structures therefore more substituted radicals are more stable.

Methyl radical (No alpha carbon, No alpha hydrogen, No hyperconjugation structures).

Ethyl radical (one alpha carbon, three alpha hydrogens, three hyperconjugation structures).

Isopropyl radical (two alpha carbons, six alpha hydrogens, six hypercojugation structures).

t-butyl radical (three alpha carbons, nine alpha hydrogens, nine hyperconjugation structures).

Hyperconjugation structures increases stability increases.

3. Chlorine reactivity is more than bromine. Thefore chlroine will react with more reactive hydrogens (tertiary hydrogens) and less reactive hydrogens (primary hydrogens).

Bromine reactivity is less. So it will react with more reactive hydrogens. It will not react with less reactive hydrogens.