# Give the decreasing order of the reaction rates of the following benzyl alcohol with $HBr$A.$I > II > III > IV$B.$IV > III > II > I$C.$II > I > III > IV$D.None of these

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Hint:We can predict the decreasing order of reaction rate of substituted benzyl alcohols with hydrogen bromide with the help of electron donating groups and electron releasing groups. We know that in case of substituted aromatic compounds, the functional group present in the compound leads the next incoming group to a particular position in the aromatic ring. We call this as the directive influence of the group already bonded to the benzene ring.

Electron donating groups are referred to as activating groups, though steric effects could inhibit the reaction. An electron withdrawing group has the opposite effect on the nucleophilicity of the ring. The electron withdrawing group takes away electron density from a $\pi$ system, thereby making it less reactive during this kind of reaction and thus called as deactivating groups.
Therefore, (III) and (IV) are less reactive when compared to (I). So, the order is $I > II > III > IV$. Option (A) is correct.