Which of the following species are 3,5 (meta) directing groups when second group is introduced into the benzene ring:I = -NH2 II = -CHO III = -COOH IV = -CH3
Correct answer: B. II and III
- A. II, III and IV
- B. II and III
- C. I and IV
- D. I, II and IV
Explanation
-CHO and -COOH are meta (3,5) directing groups as they are electron withdrawing groups in nature. As they withdraw the electron density from the aromatic ring, they make intermediate carbocations with ortho or para position less stable. Electrophiles attached at meta positions make more stable compounds.Option B is correct as -CHO and -COOH are the only groups that are 3,5 directing in this scenario. Option A, C, and D are incorrect as they include groups that are not meta directing, leading to less stable compounds when electrophiles are attached at those positions.
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About Benzene and Aromatic Compounds
Benzene has a planar ring of delocalised π electrons, giving aromatic stability and equal carbon-carbon bond lengths. The topic covers resonance, electrophilic substitution reactions such as nitration, halogenation, sulphonation and Friedel-Crafts reactions, along with substituent effects and the distinction between substitution in benzene and addition in ordinary alkenes.
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