Match List-I with List-II.

List-I (Reagents)	List-II (Reaction Name Involving Aldehydes)
A. H₂, Pd-BaSO₄$\text{H}_2, \text{Pd}-\text{BaSO}_4$	I. Etard Reaction
B. SnCl₂, HCl$\text{SnCl}_2, \text{HCl}$	II. Rosenmund Reduction
C. CrO₂Cl₂, CS₂$\text{CrO}_2\text{Cl}_2, \text{CS}_2$	III. Gatterman–Koch Reaction
D. CO, HCl, Anhyd. AlCl₃$\text{CO}, \text{HCl}, \text{Anhyd. } \text{AlCl}_3$	IV. Stephen Reaction

Choose the correct answer from the options given below:

Core Logic

The given reactant is p-hydroxybenzaldehyde, which contains both a phenolic -OH$-OH$ group (acidic) and an aldehyde group (electrophilic).

When one equivalent of Grignard reagent (PhMgBr$PhMgBr$) is added, it behaves primarily as a strong base due to the presence of an acidic proton. Acid-base reactions are extremely fast compared to nucleophilic additions.

The acidic phenolic -OH$-OH$ reacts with PhMgBr$PhMgBr$:

Upon workup with aq. NH₄Cl$aq. NH_4Cl$, the phenoxide ion simply regenerates the starting p-hydroxybenzaldehyde. However, the question asks for the number of hydroxyl groups present in the formed product (Benzene).

The distinct product formed in the reaction is Benzene. Benzene has 0 hydroxyl groups.

Pattern Recognition

Whenever a Grignard reagent encounters a molecule with an acidic hydrogen (alcohol, phenol, amine, alkyne), it will invariably act as a base first. If only 1 equivalent is used, nucleophilic addition to carbonyls will NOT happen.

Chapter Mix

Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids Class 12 Chemistry: Alcohols, Phenols and Ethers