Why is aldehydes group in benzaldehyde meta directing in nature ?

Explanation

Benzaldehyde can be considered as a resonance hybrid of following structures.

Due -R effect of aldehyde group, electron density on benzene ring decrease. Thus electrphilic substitutions in benzaldehyde occur under drastic condition. In other words -CHO group is deactivating in nature. Further the decrease in electron density is more at the o and p-positions therefore electrophilic substitution occurs only at m-position. Thus we can say that -CHO group in benzaldehyde is m-directing and deactivating.