Question

?Do the reactions below proceed in good yield from left to right as shown?

Answer 1

a) No, the reaction does not proceed in good yield from left to right. Here the reactivity of the reactant A reduced due to the reduction of the electrophilic character of the carbonyl carbon of the ester through electron delocalization as shown below. Moreover, positive inductive effect (+I effect) of the cyclohexyl group of A also reduces the electrophilic character of the ester carbonyl. 0 OCH3 + Nao O Na оснз Na o оснз

b) No, the reaction does not proceed in good yield from left to right This is an example of an esterification reaction where alcohols react with the acids to produce ester in the presence of an acid catalyst. The acid catalyst increases the reactivity through increases in the electrophilic character of the carbon atom of the carboxylic group. Without an acid catalyst, the activitv or the electrophilic character of the carboxylic carbon decreases by the +R resonance effect of the benzene ring Moreover, the presence of sodium ion from base catalystproduce the sodium salt of the corresponding carboxylic acid (A), which ultimately decreases the carbocation character/electrophilic character of the carboxylic carbon throughelectron delocalization. он ,trace of Na OCH(CH32 HO Ester Alcohol Carboxylic acid t H2O HO HO

ONa NaO c) Yes, the reaction proceeds in good yield from left to right. This is a pyridine catalyzed esterification reaction. At the first step, pyridine acts as a nucleophile through loan pair electron of its nitrogen atom and attack the carbonyl group. The process activates the carbonyl carbon for the nucleophilic attack by the alcohol. At the last stage removal of the pyridinium ion produces the corresponding product ester. The following figure of reaction mechanism shows the reaction pathways.

pyridine но NH Cl Ethanol Pyridinium; chloride Isobutyric acid ethyl ester Isobutyryl chloride Mechanism CI Cl но