Question

if a mixture of 1,4-dichlorobenzene and 2-hydroxy-5-methylbenzaldehyde is separated by column chromatography using 9:1 toluene : ethyl acetate as eluent, which compound will elute first, and why?

Answer 1

1,4-dichlorobenzene will elute first in column chromatography using 9:1 toluene: ethyl acetate, due to its lesser polarity compared to 2-hydroxy-5-methylbenzaldehyde.

Step-by-step explanation:

If a mixture of 1,4-dichlorobenzene and 2-hydroxy-5-methylbenzaldehyde is separated by column chromatography using 9:1 toluene: ethyl acetate as eluent, 1,4-dichlorobenzene will elute first. This is due to the polarity differences between the two compounds. 1,4-dichlorobenzene is a nonpolar molecule because it only has carbon-chlorine and carbon-hydrogen bonds, which makes it less interactive with the polar stationary phase (silica gel) used in column chromatography. Thus, it travels faster with the nonpolar eluent. On the other hand, 2-hydroxy-5-methylbenzaldehyde has a hydroxyl group which makes it more polar, resulting in stronger interactions with the silica and slower elution.