Question

For each of the species below, identify any cyclic conjugated system, then: A. Determine the number of electrons in a system of cyclic conjugation (zero if no cyclic conjugation). B. Specify whether the species is "a"-aromatic, "aa"-anti-aromatic, or "na"-non-aromatic (neither aromatic nor anti-aromatic). (Presume rings to be planar unless structure obviously prevents planarity. If there is more than one conjugated ring, count electrons in the largest.) осна A.Electrons in a cyclic conjugated system. B.The compound is (a, aa, or na) . A.Electrons in a cyclic conjugated system. B.The compound is (a, aa, or na) .

Answer 1

Hi we have to apply Huckel's rule of Aromaticity here. Each pi bond consists 2 electrons.

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1. Planar molecule

2. 4n+2 pi electrons

3. conjugated double bonds ---------------------------- Aromatic compound

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1. Planar molecule

2. 4n pi electrons

3. conjugated double bonds ---------------------------- Anti-Aromatic compound

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1. Non-Planar molecule ---------------------------- Non-Aromatic compound

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First molecule is 1,3,5,7-Cyclooctatetraene (COT) is non-planar molecule - Non-aromatic

Second molecule is Cyclooctadecanonaene or [18]annulene is planar and follows 4n+2 rule, hence aromatic. It's like porphyrin ring system seen in chlorophyll and it's 6 hydrogens occupy an interior & 12 "H" exterior. So - Aromatic.

For each of the species below, identify any cyclic conjugated system, then: A. Determine the number of electrons in a system of cyclic conjugation (zero if no cyclic conjugation). B. Specify whether the species is "a"-aromatic, "aa"-anti-aromatic, or "na"-non-aromatic (neither aromatic nor anti-aromatic). (Presume rings to be planar unless structure obviously prevents planarity. If there is more than one conjugated ring, count electrons in the largest.) осна >8 A.Electrons in a cyclic conjugated system. — B.The compound is (a, aa, or na) — .>na >18 A.Electrons in a cyclic conjugated system. B.The compound is (a, aa, or na) — a

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