What catalyst is typically used for Fischer esterification of a carboxylic acid with methanol?

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Multiple Choice

What catalyst is typically used for Fischer esterification of a carboxylic acid with methanol?

Fischer esterification is driven by an acid catalyst that protonates the carbonyl, making it more electrophilic for attack by the alcohol, and in an equilibrium system, removing water pushes the reaction toward the ester. Concentrated sulfuric acid is the typical choice because it provides a strong acid to speed up the protonation steps and, being hygroscopic, it also dries the mixture, removing water and shifting the equilibrium toward ester formation. Other options don’t fit as well: a base like sodium hydroxide would neutralize the acid and promote hydrolysis rather than esterification; ammonium chloride isn’t a strong enough acid catalyst; phosphoric acid can catalyze but is less effective at driving the equilibrium in this reaction.

Fischer esterification is driven by an acid catalyst that protonates the carbonyl, making it more electrophilic for attack by the alcohol, and in an equilibrium system, removing water pushes the reaction toward the ester. Concentrated sulfuric acid is the typical choice because it provides a strong acid to speed up the protonation steps and, being hygroscopic, it also dries the mixture, removing water and shifting the equilibrium toward ester formation. Other options don’t fit as well: a base like sodium hydroxide would neutralize the acid and promote hydrolysis rather than esterification; ammonium chloride isn’t a strong enough acid catalyst; phosphoric acid can catalyze but is less effective at driving the equilibrium in this reaction.

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