The major product of the following reaction is
(a) [Image]
(b) [Image]
(c) [Image]
(d) [Image]

Q: Why doesn't $Ni/H_2$ reduce the ester?

Esters are relatively unreactive towards catalytic hydrogenation compared to alkenes, alkynes, and nitriles. Reducing an ester with $H_2$ typically requires very high pressures and temperatures, or specialized catalysts like copper chromite.

Q: Why doesn't DIBAL-H reduce the ester all the way to an alcohol?

DIBAL-H is typically used at low temperatures (like $-78^\circ C$). It forms a stable tetrahedral intermediate (a hemiacetal derivative) that survives until the reaction is quenched with water, at which point it breaks down to release the aldehyde.

Q: Could the intermediate cyclize before DIBAL-H is added?

Yes, in reality, the primary amine can attack the nearby ester to form a stable lactam (isoindolin-1-one). However, DIBAL-H can also reduce lactams to cyclic hemiaminals, which exist in equilibrium with the open-chain amino aldehyde. For the purpose of this question, treating the reductions as independent events leads directly to the correct option.

Q: What if we used $LiAlH_4$ instead of DIBAL-H?

$LiAlH_4$ is a much stronger, less selective reducing agent. It would reduce the ester all the way to a primary alcohol ($-CH_2OH$), which would give us the product shown in option (d).

Q: Is the order of reagents important?

Absolutely! If we used DIBAL-H first, it would reduce the ester to an aldehyde, and it might also partially reduce the nitrile to an imine. The subsequent $Ni/H_2$ step would then reduce everything down, potentially leading to different or mixed products.

Question

The major product of the following reaction is

Sigma Percentile · Accepted Answer

The beauty of organic synthesis lies in the precision of our tools. In this problem, we are presented with a molecule containing two distinct functional groups and asked to perform a sequence of selective reductions. Let's break down the chemistry step-by-step.

### Analyzing the Setup
Our starting material is **ethyl 2-cyanobenzoate**. This molecule features a benzene ring adorned with two reducible groups at the *ortho* positions:
1. An **ester group** ($-COOEt$)
2. A **nitrile group** ($-CN$)

The challenge is to predict how these groups will respond to two very different reducing agents applied in sequence.

### The Power of Catalytic Hydrogenation
The first step involves treating the molecule with **$Ni/H_2$**. This is a classic catalytic hydrogenation condition.

Nitriles are highly susceptible to reduction under these conditions. The carbon-nitrogen triple bond is fully saturated with hydrogen, converting the $-CN$ group into a primary amine, specifically a **$-CH_2NH_2$** group.

However, ester groups are notoriously resistant to standard catalytic hydrogenation. They require much harsher conditions (like high pressure and temperature with specialized catalysts) to be reduced. Therefore, the ester group remains completely untouched during this first step. Our intermediate is ethyl 2-(aminomethyl)benzoate.

### DIBAL-H: The Precision Scalpel
In the second step, we introduce **DIBAL-H** (Diisobutylaluminium hydride). DIBAL-H is a bulky, electrophilic reducing agent celebrated for its surgical precision.

When an ester is treated with DIBAL-H at low temperatures, it is selectively reduced to an **aldehyde** ($-CHO$). Unlike stronger reducing agents like $LiAlH_4$, which would bulldoze the ester all the way down to a primary alcohol, DIBAL-H stops at the aldehyde stage. The primary amine group we formed in the first step is unaffected by DIBAL-H.

### The Final Masterpiece
Combining these two selective transformations, we arrive at our final product. The nitrile has been transformed into a primary amine ($-CH_2NH_2$), and the ester has been elegantly reduced to an aldehyde ($-CHO$).

This perfectly matches the structure shown in **option (b)**, 2-(aminomethyl)benzaldehyde. This problem is a fantastic reminder of why knowing the specific reactivity and limitations of your reagents is crucial in organic chemistry!

Animated Solution for Chemistry - Organic Chemistry: The major product of the following reaction is

Select Answer:

Visualized Solution

Analyzing the Reactant

First Reagent: $N i / H_{2}$

Second Reagent: DIBAL-H

Final Product

The Sigma Insight: Amines

Analyzing the Setup Our starting material is ethyl 2-cyanobenzoate

The Power of Catalytic Hydrogenation The first step involves treating the molecule with $N i / H_{2}$

DIBAL-H

The Final Masterpiece Combining these two selective transformations, we arrive at our final product

Similar Questions

The major product obtained in the following reaction is