Discussion
The correct order of reactivity of the following alcohols with p-nitrobenzoyl chloride in a esterification reaction is :
Answer: A
The order is III > II > I, option A.
Acylation with p-nitrobenzoyl chloride is faster for an equatorial alcohol than for an axial one, because the equatorial OH is less hindered. Locating each OH relative to the angular methyl group in the trans-decalin: in III the hydroxyl is equatorial, so III reacts fastest. In I and II the hydroxyl is axial, so both are slower than III. Of the two axial alcohols, the one in I lies on the same face as the angular methyl and is blocked by its 1,3-diaxial interaction, so I is the slowest and II comes between.
This agrees with the official key. The axial or equatorial assignment depends on the position of each OH relative to the angular methyl group as drawn.
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