Q.75 The final product A, formed in the following reaction sequence is:
$$\ce{ Ph-CH=CH2 ->[(i) BH3 (ii) H2O2,OH- (iii) HBr][(iv) Mg, ether, then HCHO/H3O+] A }$$ Options

  1. $\ce{Ph-CH2-CH2-CH2-OH}$
  2. $\begin{align}\ce{Ph-&CH-CH3} \\&| \\ &\ce{CH3}\end{align}$
  3. $\begin{align}\ce{Ph-&CH-CH3} \\&| \\ &\ce{CH2OH}\end{align}$
  4. $\ce{Ph-CH2-CH2-CH3}$

I think 3 should be the answer as carbocation formed after HBr will rearrange to get resonance stablized.

  • $\begingroup$ If it would be 3) than what would be the point of hydroboration? $\endgroup$
    – Mithoron
    Feb 8 at 15:53

1 Answer 1


It is a reasonable argument to make, but the major product will be 1.

This paper details the experiment and records over 80% yields of 2-phenethyl bromide with 5-7% of the rearrangement product.


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