Hydrolysis Rates of Esters
Purpose
Esters can be hydrolyzed to the corresponding carboxylic acid and alcohol with a decrease in the pH level as the acidic component is formed. The purpose of this experiment is to compare the hydrolysis rates of esters by monitoring the pH values of their aqueous solutions as a function of time. The esters being compared are ethyl acetate, ethyl benzoate, ethyl formate, and ethyl butanoate while the pH level can be determined by the change in color of the solution with the use of sodium hydroxide (NaOH) for the base and the universal pH indicator. The two factors that affect the rates for the hydrolysis of esters is the steric factor and the electronic factor which will serve as the determining factor of how
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Ethyl formate was the fasted to react because the pH stabilized the fastest. This may have been because the carbonyl was less sterically hindered being that it was only connected to a hydrogen allowing the nucleophile to attack the fastest. The electronic factor for ethyl formate was neutral in being electron withdrawing or electron donating, but more electron withdrawing meaning the carbonyl was more reactive. Ethyl acetate was the second ester that reacted the fasted after ethyl formate. This could have been because it was more sterically hinder since the carbonyl group was connected to a primary carbon. The third ester which reacted was ethyl butanoate since it was a bit more sterically hinder than the ethyl acetate because the carbonyl group was connected to a secondary carbon. Both ethyl acetate and ethyl butanoate had electronic factors of being electron donating making the carbonyls less reactive so the order depended more on the steric factor. The slowest ester to react was the ethyl benzoate because of the greater steric hindrance since the carbonyl was connected to a benzene ring which making it hard for the nucleophile to attack. The carbonyl was directly connected to a tertiary carbon, but that was also in a ring. The benzene is an electron