Question

Which reaction will occur at the fastest rate?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

Let us take a look at the reagent. HBr addition happens according to Markovnikovi rule. The hydrogen in HBr is added to the carbon atom (with c-c double bond) with higher number of Hydrogen atoms. $B{r}^{-}$ is added to the carbon having lesser no of Hydrogen atoms.

Endocyclic double bonds (71 bonds) are sterically difficult to access. The ring structure is more stable.

Hence the substrate in options (b) and (d) -2-Methyl but-1-ene is easier for HBr addition to take place.