Step 1: Understand what a weak -M group is. A weak -M (minus mesomeric) group is a substituent that can withdraw electrons from a molecule but does so only slightly.
Step 2: Identify examples of -M groups. Common -M groups include -CHO (aldehyde) and -COOH (carboxylic acid), which are strong -M groups.
Step 3: Compare the strength of -F (fluorine) with other -M groups. Fluorine has a slight electron-withdrawing effect but is not as strong as -CHO or -COOH.
Step 4: Conclude that -F is a weak -M group because it withdraws electrons but not as effectively as the stronger -M groups.
