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18 Nov 2019
tudent esources You learned in lecture that amides can be treated with alcohols in the presence of acid to form esters a transformation called alcoholysis that is thermodynamically unfavorable/uphill (esters are more reactive than amides) yet actually works well enough to be syntheticaly useful. The reverse transformation, treatment of esters with amines in the presence of acid to form amides, is thermodynamically favorable/downhill (amides are less reactive than esters) yet does not work well under most circumstances of the following is the most plausible explanation for this observation? odules Generalized versions of these transformations are pictured below. Which EIOH OEt Works well Does NOT NE2 work at all Alcohols are much better nucleophiles than amines, so the alcoholysis proceeds much more rapidly than the second reaction a. in the presence of acid, amines are protonated. This is good in alcoholysis, because the amine is the leaving group and protonation makes the reaction irreversible. In the second reaction, protonation renders the amine non-nucleophilic so the reaction doesn't work at all e b. Nitrogen is a better resonance donor than oxygen, so the oxygen of an amide is more basic and easily protonated than that of an ester. This makes the amide more susceptible to protonation and nucleophilic a than the ester under these conditions. o ttack Q d Oxygen is more ega ative than nitrogen, so the esters carbonyl carbon is much more electron-deficient than that of an amide. This means it will be repulsive to nearby acidic protons thus preventing attack by the amine nuckeophile. e its protonation and
tudent esources You learned in lecture that amides can be treated with alcohols in the presence of acid to form esters a transformation called alcoholysis that is thermodynamically unfavorable/uphill (esters are more reactive than amides) yet actually works well enough to be syntheticaly useful. The reverse transformation, treatment of esters with amines in the presence of acid to form amides, is thermodynamically favorable/downhill (amides are less reactive than esters) yet does not work well under most circumstances of the following is the most plausible explanation for this observation? odules Generalized versions of these transformations are pictured below. Which EIOH OEt Works well Does NOT NE2 work at all Alcohols are much better nucleophiles than amines, so the alcoholysis proceeds much more rapidly than the second reaction a. in the presence of acid, amines are protonated. This is good in alcoholysis, because the amine is the leaving group and protonation makes the reaction irreversible. In the second reaction, protonation renders the amine non-nucleophilic so the reaction doesn't work at all e b. Nitrogen is a better resonance donor than oxygen, so the oxygen of an amide is more basic and easily protonated than that of an ester. This makes the amide more susceptible to protonation and nucleophilic a than the ester under these conditions. o ttack Q d Oxygen is more ega ative than nitrogen, so the esters carbonyl carbon is much more electron-deficient than that of an amide. This means it will be repulsive to nearby acidic protons thus preventing attack by the amine nuckeophile. e its protonation and
Reid WolffLv2
24 Feb 2019