Which one of the following reactions does not represent correct combination of substrate and product under the given conditions?

Option $$\mathrm{C}$$ is incorrect.

In reaction $$\mathrm{(C)}$$, the starting compound is a primary alcohol.

Treatment with $$\mathrm{Na_2Cr_2O_7/H_2SO_4}$$ forms a strong oxidising medium.

Primary alcohols under these conditions are completely oxidised into carboxylic acids.

Hence, the actual product formed is:

$$\mathrm{p\text{-}Toluic\ Acid}$$

and not $$\mathrm{p\text{-}Tolualdehyde}$$.

Reaction $$\mathrm{(A)}$$ is the $$\mathrm{Rosenmund\ Reduction}$$, where $$\mathrm{H_2/Pd-BaSO_4}$$ selectively reduces an acid chloride into an aldehyde.

Reaction $$\mathrm{(B)}$$ uses $$\mathrm{DIBAL\text{-}H}$$, which reduces a nitrile into an aldehyde after hydrolysis.

Reaction $$\mathrm{(D)}$$ also uses $$\mathrm{DIBAL\text{-}H}$$, which selectively reduces an ester into an aldehyde.

Therefore, the incorrect reaction is:

$$\mathrm{C}$$