The major product of which of the following reaction is not obtained by rearrangement reaction ?
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Answer
(2) [figure]
Solution
(A) CH3CH2CH2Cl + anhyd. AlCl3 gives CH3CH2 CH2 (1°), which changes by a 1,2-hydride shift to (CH3)2 CH (2°) ⇒ isopropylbenzene ⇒ rearrangement.
(B) (CH3)3C-OH H+ (CH3)3C- OH2
-H2O (CH3)3 C (3°, already the most stable; no shift)
-H+ (CH3)2C=CH2 ⇒ no rearrangement.
(C) n-Hexane with anhyd. AlCl3/HCl isomerises to the branched 2-methylpentane ⇒ rearrangement (isomerisation).
(D) (CH3)3C-CH2OH gives the 1° cation (CH3)3C- CH2
⇒ 1,2-methyl shift ⇒ 3° cation (CH3)2 C-CH2CH3 ⇒ (CH3)2C=CH-CH3 ⇒ rearrangement.
∴ Only (B) gives its product without rearrangement.
Answer: (2)