Final answer:
The major product of benzaldehyde reacting with Cl2 in the presence of FeCl3 is m-chlorobenzaldehyde, due to the meta-directing effect of the aldehyde group. (Option C)
Step-by-step explanation:
The reaction of benzaldehyde with Cl₂ in the presence of FeCl₃ results in a substitution reaction where the chlorine is introduced to the benzene ring. This reaction is governed by the rules of electrophilic aromatic substitution, specifically the substitution of hydrogen by a halogen in the presence of a Lewis acid catalyst. FeCl₃ is used to generate a more reactive halogen species that can attack the aromatic ring.
Aldehyde groups, such as the one present in benzaldehyde, are meta-directing and deactivating. Therefore, the chlorine will add to the meta-position relative to the aldehyde group. Among the options provided, only m-chlorobenzaldehyde represents the meta substitution. So, when benzaldehyde reacts with Cl₂ in the presence of FeCl₃, the major product is m-chlorobenzaldehyde (option c).