Question

Write a mechanism for the acid-catalyzed hydrolysis of a THP ether to regenerate the original alcohol. Into what compound is the THP group converted?

Short answer

Answer: The mechanism for the acid-catalyzed hydrolysis of a THP ether involves the steps of protonation, nucleophilic attack by water, bond formation, and deprotonation to regenerate the original alcohol. The THP group is converted to Tetrahydropyran-2-ol.

Step-by-step solution

Understand THP ether and acid-catalyzed hydrolysis

A Tetrahydropyran (THP) ether is an ether where an alcohol molecule is bound to a tetrahydropyran ring. Acid-catalyzed hydrolysis is a reaction in which an acid speeds up the conversion of the reactive ether part back to its original alcohol form.

Protonation of THP ether

In the first step of the reaction mechanism, the lone pair of electrons on the oxygen atom of the THP ether interacts with a hydrogen ion (H+) provided by the acid catalyst. This interaction results in the protonation of the oxygen atom, making it more positively charged and electrophilic.

Nucleophilic attack by water

In the next step, a water molecule acts as a nucleophile and attacks the protonated oxygen atom of the THP ether. This forms a new bond between the oxygen atom of the water molecule and the protonated oxygen atom of the THP ether, leading to the formation of an oxonium ion intermediate.

Formation of a new bond with the THP ring

The intermediate formed in the previous step now has a positively charged oxygen atom with three bonds. It will try to revert to its neutral state by breaking one of its bonds. This bond cleavage results in the formation of a bond between the other oxygen atom from the water molecule and the carbon atom of the THP ring.

Deprotonation and regeneration of the alcohol

In the final step, the oxygen atom bonded to the carbon of the THP ring loses a hydrogen ion (H+). This loss of a hydrogen ion results in the regeneration of the original alcohol and the release of a proton that can continue to catalyze the reaction.

Identify the compound formed from the THP group

After the cleavage of the ether bond and the formation of the original alcohol, the THP group is converted into Tetrahydropyran-2-ol. This is the compound formed from the THP group during the acid-catalyzed hydrolysis of the THP ether. So, the mechanism for the acid-catalyzed hydrolysis of a THP ether involves the steps of protonation, nucleophilic attack by water, bond formation, and deprotonation to regenerate the original alcohol. The THP group is converted to Tetrahydropyran-2-ol.