(A)Say whether true or false and give valid explanation:
1) Iodine does not react with CH4 at all
2)The energy of activation of
Cl.+CH4 → HCL + CH.3 is smaller than that of
Br.+CH4 → HBR + CH.3
(for clarification: here there is clorine free radical,methyl free radical & bromine free radical)
(B)Of the C6H5CH3 , (CH3)3CH, (CH3)2CHCH3 and 
(PROPENE) ; the maximum ease of abstraction of hydrogen atom is shown by which of the above three hydrcarbons? Give reasons for the answer.
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1 Answers
392) By the Reactivity-Selectivity principle, as the bromine free radical is less reactive than the chlorine radical, it is more selective on which hydrogen site it will attack. Thus a greater activation energy is required for the desired product.
1)Iodine free radicals are very unstable, and they combine to form molecular iodine instead. Also, by the RS principle, iodine is least reactive/not reactive at all.
3)PhCH3 leads to the formation of a benzylic radical, which is stabilised by resonance. Tert-butyl radical is stabilised by hyperconjugation.
As hyperconjugation is given more preference, tert butyl radical is more stable than benzyl radical, and the stability order follows that of carbocations. Additionally tert-butyl radical has the most hyperconjugation structures, and is most stable.