In: Chemistry
Draw the product(s) formed by heating the following compound in acidic methanol.
Concepts and reason
Transesterification is a reaction process where the ester reacts with the alcohol in acid catalyst and heat to produce a new ester and alcohol. In this process, the ester can be converted into other esters using the alcohol group with an acid catalyst.
Fundamentals
Transesterification: Ester conversion to the other ester in the presence of acid catalyst and heat is known as transesterification.
Acid catalyst protonates the carbonyl oxygen in the ester functional group, which leads to oxonium ion. Then, carbonyl electrons are moved towards the oxonium ion while the alcohol group attacks the positively charged carbon in the carbonyl, leading to the formation of a new ester.
From the given ester, the structure is shown below.
The protonation of the ester by acid is as follows.
Alcoholic group (methanol) attacks the carbonyl group and forms tetrahedral intermediate.
The acid protonates given ester to form an oxonium ion. The positive charge on oxonium ion attracts the bonded electron pair towards itself, which causes the attack of the methanol group on the positively charged carbon in the carbonyl group to give the tetrahedral intermediate.
Deprotonating the tetrahedral intermediate is as follows.
Acid/base reaction is a process where protonation occurs at non-carbonyl oxygen to make methoxide ion to methanol as a good leaving group.
The leaving group goes out by electrons' movement from the adjacent oxygen and forms oxonium ion, which leads the ester by deprotonation.
Deprotonating of the oxonium ion as follows.
The complete transesterification reaction
The tetrahedral intermediate formed through the methanol attack on the oxonium ion, which is formed through the protonation of the ester by an acid. This tetrahedral intermediate further undergoes acid/base reaction through deprotonating at carbonyl oxygen and protonation at non-carbonyl oxygen. This leads to a new ester by leaving the alcohol group.
Complete trans esterification reaction