Propose a mechanism for each of the following reactions:

In an acidic solution, the acid protonates an oxygen of the acetal. This creates a weak base (CH₃OH) that can be eliminated. When the group is eliminated, water can add to the highly reactive intermediate, and the formation of ketone or aldehyde takes place.

In the first step of the reaction protonation happens, the oxygen atom of carbonyl is protonated by mineral acid HB from the solution. then nucleophile attacks the carbonyl carbon and stabilize the charge on oxygen atom.

In the next step of the reaction mineral acid ion deprotonated the oxygen atom of hydroxyl (OH) group. Then further protonation of oxygen atom of carbonyl group takes place by acid HB.This creates a weak base (CH₃OH) that can be eliminated. When the group is eliminated, formation of ketone or aldehyde takes.

The detailed mechanism of the reaction (a) is shown below in the figure:

In this reaction (b), the acid protonates the carbonyl oxygen, making the carbonyl carbon more susceptible to nucleophilic addition.

Then alcohol adds to the carbonyl carbon.

Loss of a proton from the protonated intermediate forms the neutral intermediate and we get the desired product as shown in the figure.

The detailed mechanism of the reaction (b) is shown below in the figure: