Molecular orbitals 10 -annulene

Nonbenzenoid cyclic conjugated hydrocarbons are conveniently classified into two categories conjugated hydrocarbons composed of odd-membered rings called, in terminology of molecular orbital theory, nonalternant hydrocarbons, and cyclic polyenes currently known as annulenes. 

E. Heilbronner, Tetrahedron Lett. 5, 1923 (1964). Hiickel Molecular Orbitals of Mobius-Type Conformations of Annulenes. 

A molecule with An n electrons in the ring, with the molecular orbitals made up from An p orbitals, does not show this extra stabilisation. Molecules in this class that have been made include cyclobutadiene 1.13 (n = 1), the cyclopentadienyl cation 1.14, cyclooctatetraene 1.15 andpentalene 1.16 (n 2), [12]annulene 1.17 (n = 3) and [16]annulene 1.18 (n A). 

Heilbronner, E. Hiickel molecular orbitals of Mobius-type conformations of annulenes, Tetrahedron Lett. 1964, 5,1923-1928. 

Fig. 1. Huckel 7c-elcctron molecular orbitals for some lower annulenes...

Fig. 6. Htickel ir-electron molecular orbitals for some charged annulenes... 

Molecular orbitals allyl cation, 397 [10]-annulene, 425 benzene, 407, 424 bonding and antibonding, 34—35 1,3-butadiene, 397—398 cyclobutadiene, 424 cycloheptatrienyl cation, 427—428 cis, tram -1,3-cyclooctadiene, 524 cyclooctatetraene, 424 cyclopentadienide anion, 428 ethylene, 386—397 frontier, 386... 

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