Question

QUESTION REVIEW Question 6 Status: Not yet answered I Points possible: 1.00 Aspirin synthesis involves the addition of an acetyl group to salicylic acid in a condensation reaction with an alcohol. The acety group could be added with a carboxylic acid but the preferred procedure is to use the acid anhydride. Why is preferable to use an acid anhydride for ester formation with an alcohol rather than a carboxylic acid? Select one: ОО Acid anhydrides are less stable than esters so the equilibrium favors the ester product. Carboxylic acids change the pH of the solution too much for the reaction to proceed O Carboxylic acids react with water in an undesired side reaction Acid anhydrides are generally easier and safer to handle than carboxylic acids. NEXT Question 6 of 7 < BACK 9 0 S 4 5 6 7 3 2 Р a Y E R Н. J K G F S D M

Answer 1

Acid anhydrides are less stable than esters so the equilibrium favors the ester product.

Anhydrides are less stable because the donation of electrons to one carbonyl group is in competition with the donation of electrons to the second carbonyl group. Thus, in comparison to esters, where the oxygen atom need only stabilize one carbonyl group, anhydrides are more reactive than esters.

To prepare aspirin, salicylic acid is reacted with an excess of acetic anhydride. A small amount of a strong acid is used as a catalyst which speeds up the reaction. ... The aspirin product is not very soluble in water so the aspirin product will precipitate when water is added.