Step 1: Understand what a -M group is. A -M group (minus mesomeric group) is a substituent that withdraws electron density from a molecule through resonance.
Step 2: Identify the group in the question. The group given is -NO2 (nitro group).
Step 3: Analyze how -NO2 behaves. The -NO2 group has a strong ability to pull electron density away from the rest of the molecule due to its structure.
Step 4: Confirm that -NO2 withdraws electron density through resonance. This means it can stabilize the molecule by delocalizing electrons.
Step 5: Conclude that since -NO2 withdraws electron density effectively, it is classified as a strong -M group.
