Question

Write the name of the reagent to convert Ethanenitrile to Ethanal.

Hint:

Converting a nitrile (R-C≡N) to an aldehyde (R-CHO) needs a partial (controlled) reduction that stops at the aldehyde stage and does not go all the way to an amine.

Answer 1

Concept: Converting a nitrile (R-C≡N) to an aldehyde (R-CHO) needs a partial (controlled) reduction that stops at the aldehyde stage and does not go all the way to an amine. A mild, selective reducing reagent is required, and the imine intermediate is then hydrolysed with water.
Answer: The reagent is stannous chloride and hydrochloric acid (SnCl₂/HCl), followed by hydrolysis with water. This is the Stephen reduction. Ethanenitrile (CH₃-C≡N) is first reduced to an imine salt, which on hydrolysis gives ethanal (CH₃-CHO). (Diisobutylaluminium hydride, DIBAL-H, followed by water is also an accepted reagent for this partial reduction.)