See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Concept: The +M (positive mesomeric) effect refers to groups that donate electron density into the aromatic ring through resonance (pi-electron donation). These are groups that have lone pairs on the atom directly attached to the ring, which can be delocalized into the ring via conjugation. Step 1: Identify which groups exhibit the +M effect (donate electrons to ring by resonance): - +M groups are those where the atom attached to the ring has lone pairs that can be pushed into the ring, increasing electron density. - Common +M groups: -OH, -OR (alkoxy), -NH2, -NHR, -NR2, -O(-), halogens (weak +M), etc. Step 2: Analyze each substituent: (a) -OH: Oxygen has lone pairs donated into ring → +M group. COUNT: YES (b) -NH2: Nitrogen has lone pairs donated into ring → +M group. COUNT: YES (c) -NO2: Nitrogen withdraws electrons from ring via resonance → -M group. COUNT: NO (d) -C(=O)-CH3 (acetyl): Carbonyl withdraws electrons from ring via resonance → -M group. COUNT: NO (e) -OCH3: Oxygen has lone pairs donated into ring → +M group. COUNT: YES (f) -NH-CH3: Nitrogen has lone pairs donated into ring → +M group. COUNT: YES (g) -SO3H (sulfonyl): Sulfur withdraws electrons from ring via resonance → -M group. COUNT: NO (h) -CHO (aldehyde): Carbonyl withdraws electrons from ring via resonance → -M group. COUNT: NO Step 3: Count the +M groups: (a) -OH: +M ✓ (b) -NH2: +M ✓ (e) -OCH3: +M ✓ (f) -NHCH3: +M ✓ Total = 4 Step 4: Why others fail: -NO2 is a strong -M group (withdraws via N=O resonance). -COCH3 is a -M group (carbonyl withdraws via conjugation). -SO3H is a -M group (sulfonyl withdraws via S=O resonance). -CHO is a -M group (aldehyde carbonyl withdraws via conjugation). Therefore, the correct answer is 4.