Question

$CH_3​−CH=CH−CH_2​−CN \xrightarrow[{{H}_{2}}O]{DIBALH} Product$. Then the product is:

Answer 1

Hint: DIBALH (Di-isobutyl Aluminium Hydride) is a strong, bulky reducing agent which is used for the partial reduction of esters. It reduces esters to aldehydes. Nitriles are typically converted to aldehydes using the hydride reagent DIBAL-H as well.

Complete step by step solution:
The reaction of conversion of nitrile to aldehyde begins with the formation of an iminium anion by adding a hydride to the C-N triple bond. The formed imine salt then hydrolysed to form imine.

After the first hydride addition, hydrolysis of the imine to amine takes place through the nucleophilic attack of H₂O.

The Amine group leaves the substrate when OH attacks it as a nucleophile and forms a double bond. In the last step H₂O takes out the extra H from the substrate and an aldehyde is formed.

The product is CH₃−CH=CH−CH₂−CHO.

Additional Information: According to the suggested mechanism, DIBAL joins the nitrile through the creation of an N-Al link to form a Lewis acid-base adduct. The hydride is subsequently transferred to the nitrile's carbon. Aldehyde and ammonia are produced during aqueous workup as desired.

Note: In contrast to lithium aluminium hydride, Di-isobutyl Aluminium Hydride (DIBAL H) won't reduce the aldehyde anymore with the addition of just one equivalent. Other carbonyl substances including amides, aldehydes, ketones, and nitriles will also be reduced by it. DIBAL is most notable for what it does not do, much like Lindlar's catalyst is. It lowers esters but doesn't get all the way to alcohol; it just stops at aldehyde. The temperature is kept very low(-70° C) for the reaction to keep the reactivity in check.