Question
Why is that absolute ethanol be used in preparing an ester with ethanol as one of the reactants?
My Guess:
It will cause hydrolysis of the ester as it is formed in the reaction vessel.
Is this reasoning right? Pls. I need help about this...
My Guess:
It will cause hydrolysis of the ester as it is formed in the reaction vessel.
Is this reasoning right? Pls. I need help about this...
Answers
DrBob222
The preparation of an ester using a carboxylic acid and an alcohol is an equilibrium reaction involving
RCOOH + HOR' ==> RCOOR' + H2O.
For acetic acid and ethanol, the products are approximately 2/3 mole each of ester and water and the reactants are about 1/3 mole each of the starting materials. The equilibrium mixture is favored to the right (about 67% yield) but not all that much. Adding water (by not using <i>absolute</i> ethanol BOTH drives the reaction to the left (less yield) (LeChatelier's Principle) and provides an easier path for hydrolysis (the reverse direction of esterification).
RCOOH + HOR' ==> RCOOR' + H2O.
For acetic acid and ethanol, the products are approximately 2/3 mole each of ester and water and the reactants are about 1/3 mole each of the starting materials. The equilibrium mixture is favored to the right (about 67% yield) but not all that much. Adding water (by not using <i>absolute</i> ethanol BOTH drives the reaction to the left (less yield) (LeChatelier's Principle) and provides an easier path for hydrolysis (the reverse direction of esterification).