Kinetics of Iodination of Acetone, what was the acid catalyst used in the reaction?
Select one:
a. Phosphoric acid
b. Acetic acid
c. Hydrochloric acid
d. Nitric acid
The correct answer and explanation is:
The correct answer is c. Hydrochloric acid.
The iodination of acetone is an example of a reaction where the presence of an acid catalyst is essential to facilitate the reaction. In this particular case, hydrochloric acid (HCl) is commonly used as the acid catalyst in the iodination of acetone. This reaction involves the substitution of a hydrogen atom on the acetone molecule with an iodine atom, and the acid catalyst plays a significant role in increasing the rate of reaction.
The mechanism of the iodination of acetone typically proceeds through a protonation step. The reaction begins with the protonation of acetone by the acid, which makes the carbonyl carbon more electrophilic and more susceptible to nucleophilic attack by the iodide ion (I⁻). Once the acetone is protonated, the iodine ion from the iodination reagent attacks the carbonyl carbon, leading to the substitution of one of the hydrogen atoms with iodine.
The presence of hydrochloric acid provides a medium for this process, stabilizing intermediates and speeding up the overall reaction. Other acids like phosphoric acid, acetic acid, or nitric acid may not be as effective because they either do not protonate the acetone as efficiently or do not facilitate the necessary conditions for the iodination to proceed as rapidly. Hydrochloric acid is particularly effective because it provides a suitable concentration of hydrogen ions to assist in the electrophilic nature of acetone.
The reaction proceeds under mild conditions and is an example of an electrophilic substitution, where the catalyst does not get consumed but accelerates the overall process. The concentration of the acid and the iodine are key factors that determine the reaction rate in this iodination process.