Phenol is treated with chloroform in the presence of aqueous sodium hydroxide, followed by acidification. The reaction yields two isomeric products. Which of the following is the most appropriate method to separate these two isomers?

Step-by-step solution

The reaction described is the Reimer-Tiemann reaction. Phenol reacts with CHCl ₃ and aqueous NaOH to form ortho-hydroxybenzaldehyde (salicylaldehyde) as the major product and para-hydroxybenzaldehyde as the minor product. Salicylaldehyde exhibits intramolecular hydrogen bonding, which prevents association between molecules, making it more volatile (steam volatile). Para-hydroxybenzaldehyde exhibits intermolecular hydrogen bonding, leading to molecular association, which decreases its volatility (not steam volatile)