The Fischer Esterification Recall that acid and alcohol->ester and water The overall transformation is that the-OH of an acid is replaced by the-OR'of an alcohol. E.g. 0 0 R-C-OH RO-H H R-COR 4HO The Fischer esterification is an example of acid catalyzed nucleophilic acyl substitution The carbonyl group of a carboxylic acid is not sufficiently electrophilic to be attacked by the alcohol. H :ǒ-H :0-H R -OH三R-C-OH+R'OH :OR R'一OH ester hydrate (Species in brackets are resonance-stabilized.) The acid catalyst protonates the carbonyl oxygen,and activates it toward nucleophilic attack. The alcohol attacks and after deprotonation of the alcohol oxygen,the hydrate of an ester is formed. The ester is produced via acid catalyzed dehydration of the ester hydrate. Ch20 Carboxylic Acids (landscape) Page 19Ch20 Carboxylic Acids (landscape) Page 19 The Fischer Esterification Recall that acid and alcohol  ester and water The overall transformation is that the -OH of an acid is replaced by the -OR' of an alcohol. E.g. The Fischer esterification is an example of acid catalyzed nucleophilic acyl substitution. The carbonyl group of a carboxylic acid is not sufficiently electrophilic to be attacked by the alcohol. The acid catalyst protonates the carbonyl oxygen, and activates it toward nucleophilic attack. The alcohol attacks and after deprotonation of the alcohol oxygen, the hydrate of an ester is formed. The ester is produced via acid catalyzed dehydration of the ester hydrate. R C O O-H R C O R O-R' '-O-H +H2O H +