Structure of benzene: Kekulé forms, resonance hybrid, π cloudबेन्ज़ीन की संरचना: केकुले रूप, अनुनाद संकर, π मेघ

NCERT Sec 9.5.2–9.5.3 · interactive diagram

Parts and their functions

• Kekulé structures (केकुले संरचनाएँ) — Kekulé (1865) drew a hexagon with alternate single and double bonds. Two such structures differ only in the positions of the double bonds — they are resonance structures.
• Resonance hybrid (अनुनाद संकर) — The real molecule is the hybrid, shown by a circle in the hexagon. All six C–C bonds are equal (139 pm), between C–C (154 pm) and C=C (133 pm).
• Orbital picture (कक्षक चित्र) — Each carbon is sp²; the six unhybridised p orbitals overlap all round the ring, giving a delocalised π cloud above and below the plane. Delocalisation makes benzene extra stable, so it prefers substitution to addition.
• Hückel rule (हकल नियम) — A compound is aromatic if it is planar, cyclic, has complete delocalisation of π electrons and contains (4n + 2) π electrons (n = 0, 1, 2…). Benzene (6), naphthalene (10) and the cyclopentadienyl anion (6) qualify.

Original diagram drawn by Simple Learning Hub, based on NCERT Sec 9.5.2–9.5.3. Report a mistake