Role of π stabilization in cyclic polyenes

✍ Scribed by Sven Larsson; Lucía Rodríguez-Monge

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 155 KB
• Volume: 67
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(1998)67:2<107::aid-qua5>3.0.co;2-z

✦ Synopsis

The Huckel model with bond-length-dependent coupling ␤ , contrary ẗo the original Huckel model with a constant ␤, may be parametrized to give C᎐C bond lengths and some other properties in good agreement with accurate ab initio results. The paradox in seemingly contradictory conclusions of some recent works on whether the electrons promote equal bond lengths or bond alternation in benzene is discussed for the more general group of cyclic polyenes. We find that electrons promote bond alternation but that the interaction between electrons of different bonds always leads to a decrease Ž . of the bond length alternation in cyclic systems except C H compared to the difference 4 4 in bond length between pure single and double bonds.