Question

The major product of the above reaction is:

(A) A hemiacetal
(B) An acetal
(C) An ether
(D) An ester

Answer 1

Hint: A hemiacetal is a compound in which the same carbon has an alcohol group and $-OR$ group. An acetal is a compound in which the same carbon atom has two $-OR$ groups. In the above reaction double bond will be replaced with $-OC{{H}_{2}}R$ group.

Complete step by step solution:
So, in the reactant, there is an oxygen atom that has two lone pairs present. Now the lone pair will transfer to the next bond-forming a double bond, the double bond will be attacked by the hydrogen ion because the reaction is taking place in acid. This will form a negative charge on the carbon atom next to the oxygen atom.
Now the reactant $HOC{{H}_{2}}R$, the oxygen atom has two lone pairs. So the lone pair of the oxygen atom will attack the negative charge of the carbon and the $-OC{{H}_{2}}R$ group will be attached.
The reaction is given below:

Here in this compound, the same carbon atom has two $-OR$ groups, therefore, it is an acetal.

Therefore, the correct answer is an option (B) An acetal.

Additional information:
A hemiacetal is a compound in which the same carbon has an alcohol group and $-OR$ group. Ether is a compound in which two alkyl groups are joined by one oxygen atom. An ester is a compound in which the functional group between two alkyl groups is $-COO-$.

Note: In an acetal compound the R group can be the same or different, but it must be on the same carbon atom. The above reaction can only take place in the presence of acid.