Discussion
The rates of alkaline hydrolysis of the compounds shown below
follow the order:
Answer: C
The order is II \(\gt\) III \(\gt\) I.
The t-butyl group locks each ring in the chair with t-Bu equatorial. In II the ester is trans to t-Bu (one wedge, one hash, 1,4), so it is also equatorial. In III the ester is cis to t-Bu (both wedges), so it is forced axial.
Alkaline hydrolysis goes through a crowded tetrahedral intermediate at the carbonyl carbon. An equatorial ester is less hindered than an axial one, which suffers 1,3-diaxial interactions, so II reacts faster than III. Compound I is an amide: the nitrogen lone pair is strongly delocalised into the carbonyl and NH2− is a very poor leaving group, so amides are hydrolysed far more slowly than esters whatever their conformation.
Any order placing I first, or III ahead of II, contradicts these two effects.
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