Question

The major product obtained in the following reaction is:

A.
B.
C.
D.

Answer 1

We can deduce the major product by having a look at the given reactant and the reagent, ${\rm{DIBAL}} - {\rm{H}}$ that we can use for selective reduction.

Complete answer:
Let’s have a look at our given reactant which has the following structure:

As we can see that in this given reactant, we have two double bonds, one carboxylic acid group and one lactone group that can be reduced. Now we will consider the given reagent.
In synthetic chemistry, we have many reagents that can be used for selective reduction of different groups. One such reagent is our given diisobutylaluminum hydride that we also know as ${\rm{DIBAL}} - {\rm{H}}$. We can use diisobutylaluminum hydride for selective reduction of lactone to give lactol, esters and carboxylic groups to the aldehyde group in our given reactant to the aldehyde group.
Let’s write the chemical reaction for partial reduction of our given reactant by diisobutylaluminum hydride as follows:

As we can see that double bonds remained intact in the molecule whereas other two groups have reduced to give the major product.

**Hence, the correct option is A.

Note: **
We can use diisobutylaluminium hydride to carry out other selective reductions as well such as conversion of nitriles to imines.