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Unformatted text preview: 562 CARBOXYLIC ACID DERIVATIVES: NUCLEOPHILIC ACYL SUBSTITUTION ( j) A Hofmann rearrangement of benzamide affords aniline.
[prepared as in part (d )] HO NH2 H2 O Bromine Aniline O
The problem speciﬁes that CH3CH2COCH2CH3 is to be prepared from 18O-labeled ethyl alcohol
(O 18 O) .
O O CH3CH2CCl CH3CH2O
O Ethyl alcohol Ethyl propanoate Thus, we need to prepare 18O-labeled ethyl alcohol from the other designated starting materials,
acetaldehyde and 18O-enriched water. First, replace the oxygen of acetaldehyde with 18O by the
hydration–dehydration equilibrium in the presence of 18O-enriched water.
O O OH CH3CH H2O Acetaldehyde 18O-enriched CH3CH H2O 18O-enriched Water CH3CH
acetaldehyde water acetaldehyde Once 18O-enriched acetaldehyde has been obtained, it can be reduced to 18O-enriched ethanol.
CH3CH 20.31 (a) NaBH4, CH3OH
2. H2O CH3CH2OH The rate-determining step in basic ester hydrolysis is nucleophilic addition of hydroxide ion
to the carbonyl group. The intermediate formed in this step is negatively charged.
CH3COCH2CH3 HO CH3COCH2CH3
OH Ethyl acetate Hydroxide
intermediate The electron-withdrawing effect of a CF3 group stabilizes the intermediate formed in the ratedetermining step of ethyl triﬂuoroacetate saponiﬁcation.
CF3COCH2CH3 HO CF3COCH2CH3
OH Ethyl triﬂuoroacetate Hydroxide
intermediate Because the intermediate is more stable, it is formed faster than the one from ethyl acetate. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website ...
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