(d)A cyano group is strongly electron-withdrawing, and so 4-cyanophenol is a stronger acid thanphenol.There is resonance stabilization of the 4-cyanophenoxide anion.(e)The 5-nitro group in 2,5-dinitrophenol is meta to the hydroxyl group and so does not stabilizethe resulting anion as much as does an ortho or a para nitro group.24.15(a)The rate-determining step of ester hydrolysis in basic solution is formation of the tetrahedralintermediate.Because this intermediate is negatively charged, there will be a small effect favoring its for-mation when the aryl group bears an electron-withdrawing substituent. Furthermore, this in-termediate can either return to starting materials or proceed to products.The proportion of the tetrahedral intermediate that goes on to products increases as the leav-ing group ArObecomes less basic. This is strongly affected by substituents; electron-
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