(d)The hydroxyl group may be on the same side as the double bond or on the opposite side.The anti alcohol is observed to be formed in greater amounts (85:15) on reduction of the ke-tone with LiAlH4. Steric factors governing attack of the hydride reagent again explain themajor product observed.17.24(a)Aldehydes undergo nucleophilic addition faster than ketones. Steric crowding in the rate-determining step of the ketone reaction raises the energy of the transition state, giving rise toa slower rate of reaction. Thus benzaldehyde is reduced by sodium borohydride more rapidlythan is acetophenone. The measured relative rates are(b)The presence of an electronegative substituent on the a-carbon atom causes a dramatic in-crease in Khydr. Trichloroethanal (chloral) is almost completely converted to its geminal diol(chloral hydrate) in aqueous solution.Electron-withdrawing groups such as Cl3C destabilize carbonyl groups to which they are at-
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