3. How would each of the following shift the equilibrium in the esterification r

Question

3. How would each of the following shift the equilibrium in the esterification reaction between an alcohol and a carboxylic acid? . Remove H O as it is formed .Add an acid catalyst 4. Explain how Le Chatelier's Principle is used in our experiment to tip the reaction toward product formation? 2. In today's experiment the esterification is performed by using a mixture of acetyl chloride and acetic anhydride instead of acetic acid. a. What is the purpose of substituting acetic acid with acetic anhydride / acetyl chloride mixture? b. Could only acetic anhydride be used by itself instead of the mixture acetic chloride + acetic anhydride mixture? 3. Give the chemical reasons for the following steps in the synthesis of 4-t-butylcyclohexyl acetate a. Using clean and not wet glassware to perform the reaction b. Using both acetic anhydride and acetyl chloride. c. Adding a spin vain d. Heating (refluxing) the mixture after adding the alcohol, anhydride and acetyl chloride. What is refluxing? Extracting with a mixture of Et20 and 5% sodium bicarbonate solution. A student added anhydrous sodium sulfate to his combined extracts and the sodium sulfate e. f. dissolved. What error did the student make in the experiment? What should he do now?

Explanation / Answer

3. How would each of the following shift the equilibrium in esterification reaction between the an alcohol and a carboxylic acid:

Alchohol (R-OH) + carboxylic acid (R'-COOH) -------> Ester (R'COOR) + Water (H2O)

Remove H2O as it is formed:

Removing water as it is formed would shift the equilibrium to the right, ie towards formation of ester. This happens because above reaction is reversible in presence of water. So the ester formed would be converted back to alcohol and carboxylic acid. If water is removed as it is formed, the ester formed would remain in its form and hence equilibrium is shifted to right.

Add an acid catalyst:

Adding an acid catalyst also would shift the equilibrium to the right, ie towards formation of ester. The carbonyl of the acid would be protonated by the acid, there by activating the carbon end of the carbonyl for nucleophilic attack by the OH group from alcohol. Since it is a catalyst it would be regenrated in the reaction to activate another molecule of acid and the process repeats. So addition od acid catalyst increases the formation of ester.

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