Consider the following reaction. The structure of the major reaction intermediate formed in the above reaction

Question

Consider the following reaction. The structure of the major reaction intermediate formed in the above reaction is-

Accepted Answer

1. **Reaction Context:** The question refers to a reaction involving the formation of a free radical intermediate, typical of **free radical halogenation of alkanes** (e.g., bromination) .
2. **Stability of Free Radicals:** The stability of alkyl free radicals follows the order: **Tertiary ($3^\circ$) > Secondary ($2^\circ$) > Primary ($1^\circ$)**. This stability order is due to the hyperconjugation effect and the inductive effect of the alkyl groups attached to the carbon bearing the unpaired electron .
3. **Selectivity:** In free radical substitution reactions (especially bromination), the major product is derived from the most stable intermediate.
4. **Analysis of Options:**
   - The reactant appears to be an isomer of a deuterated alkane, likely 2-methyl-3-deuterobutane ($H_3C-CH(D)-CH(CH_3)_2$).
   - **Option 2** represents a **tertiary ($3^\circ$) free radical** ($H_3C-CH(D)-\dot{C}(CH_3)-CH_3$), formed by the abstraction of the hydrogen atom from the tertiary carbon.
   - Other options represent primary or secondary radicals, which are energetically less stable.
5. **Conclusion:** Since the tertiary radical is the most stable, it will be the major reaction intermediate, leading to the major product.

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