In the reaction with HCl, an alkene reacts in accordance with the Markovnikov's rule to give a product 1-chloro-1-methylcyclohexane. The possible alkene is
- [figure] (A)
- [figure] (B)
- (A) and (B)
- [figure]
Answer
(3) (A) and (B)
Solution
As per NCERT, in the addition of HX to an unsymmetrical alkene (Markovnikov's rule), the negative part (Cl-) goes to the double-bond carbon carrying fewer hydrogen atoms, through the more stable carbocation.
(A) Methylenecyclohexane: H+ adds to =CH2 ⇒ 3° carbocation at the ring carbon ⇒ Cl- attacks it:
[figure]
(B) 1-Methylcyclohexene: H+ adds to C-2 ⇒ 3° carbocation at C-1 (bearing CH3) ⇒ the same product:
[figure]
(D) 3-Methylcyclohexene gives a 2° carbocation not at the carbon bearing CH3 ⇒ 1-chloro-2-methyl- / 1-chloro-3-methylcyclohexane, not 1-chloro-1-methylcyclohexane.
∴ Both (A) and (B) give 1-chloro-1-methylcyclohexane.
Answer: (3)