What is the product obtained when Pent-3-enenitrile is treated with...

The structure of Pent-3-enenitrile is $\text{CH}_3\text{-CH=CH-CH}_2\text{-CN}$.

DIBAL-H (Diisobutylaluminium hydride) is a selective reducing agent that reduces nitriles to imines. Upon subsequent acid hydrolysis, the imine is converted to an aldehyde.

DIBAL-H does not reduce isolated carbon-carbon double bonds.

Therefore, the $\text{-CN}$ group is converted to a $\text{-CHO}$ group, while the double bond remains intact.

The product formed is Pent-3-enal, which has the structure $\text{CH}_3\text{-CH=CH-CH}_2\text{-CHO}$.

Answer: $\text{CH}_3\text{-CH=CH-CH}_2\text{-CHO}$