Q12-47E - Organic Chemistry (Mcmurry)

Question

Nitriles,  $\mathbf{R}\mathbf{-}\mathbf{C}\equiv \mathbf{N}$, undergo a hydrolysis reaction when heated with aqueous acid. What is the structure of the compound produced by hydrolysis of propanenitrile, ${\mathbf{CH}}_{\mathbf{3}}{\mathbf{CH}}_{\mathbf{2}}\mathbf{C}\equiv \mathbf{N}$, if it has IR absorptions from $\mathbf{2500}\mathbf{-}\mathbf{3100}{\mathbf{cm}}^{\mathbf{-}\mathbf{1}}$ and at $\mathbf{1710}{\mathbf{cm}}^{\mathbf{-}\mathbf{1}}$, and has ${\mathbf{M}}^{\mathbf{+}}\mathbf{=}\mathbf{74}$?

Step-by-Step Solution

Answer

Step 1: IR spectroscopy

The N-H functional group of amine can be easily detected using the IR spectroscopy. It shows a characteristic absorption in the range 3300 to 3500 cm^-1. An N-H absorption band is less intense in comparison to the O-H absorption band.

Step 2: Structure of the compound from the given data

The m/z value of the product is 74. The IR spectrum shows that the compound has IR absorptions at the values ${\text{2500 - 3100 cm}}^{\text{ - 1}}$ and at ${\text{1710 cm}}^{\text{ - 1}}$.

When the nitrile undergoes hydrolysis forms carboxylic acid. The given propane nitrile, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{C}\equiv \text{N}$ undergoes hydrolysis to give propionic acid.

IR absorptions at the values from ${\text{2500 - 3100 cm}}^{\text{ - 1}}$ indicates the hydroxyl group at the carboxylic acid. The value at ${\text{1710 cm}}^{\text{ - 1}}$ indicates the carbonyl group of the carboxylic acid functional group.

Reaction of nitrile with ${\text{H}}_{\text{3}}{\text{O}}^{\text{ + }}$ and heat

The molecular weight of the compound matches with the expected compound. The structure of the compound can be given as: