Question

1)You are instructed to reflux the reaction for 1 hour. If the instructions simply told you to reflux until the reaction was complete, how would you know when this was?Questions regarding Organic Chemistry Lab: Fischer Esterification

2)Why do we wash the organic with aqueous base? Is acetic acid water soluble (how do you know)? If it is water soluble, why don’t we just wash with water instead of aqueous base?

3)In most cases of Fischer esterification, the carboxylic acid is the more “valuable” piece and the alcohol is used in excess. Let’s say you are making the ethyl ester of an acid and use the ethanol in excess. What technique would be used to remove the excess ethanol?

Thanks in advance!

Answer 1

Fisher esterification is part of nucleophilic acyl substitution reaction. Basically it is dealing with electrophilicity of carbonyl carbon of carboxylic acid and nucleophilicity of alcohol. The carboxylic acid and alcohol are combine to give the ester by in which the products and reactants are in equilibrium.

To give the equilibrium , it needs time which indicate the completion of reaction.

The equilibrium may be influenced by either removing one product from the reaction mixture or by treating an excess of one reactant.This equilibrium can be maintained under reflux.

To get equilibrium the solution would need to be refluxed until/unless the maximum rate of equilibrium is achieved in order to yield the highest amount of ester which will show the equilibrium constant at a given temperature . As Le Chatlier’s principle states that this reaction is reversible, using one of the reagents in excess helps the equilibrium shift towards forward reaction to favor the production of the desired amount of ester. If this reaction were to proceed, the product formed would not only contain an ester but also give residual alcohol and acid as well.

Here the solution under reflux for 1 hr and the completion of reaction show that the equilibrium is maintained so that maximum yield can be obtained.

The reaction and mechanism of Fischer Esterification can written as:

this is the answer of question number 1.