Carbodications. I. The structures and energies of C4H isomers

✍ Scribed by Jayaraman Chandrasekhar; Paul Von Ragué Schleyer; Karsten Krogh-Jespersen

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 393 KB
• Volume: 2
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.540020316

✦ Synopsis

At high levels of ab initio theory (6-31G*//4-31G), the most stable C4H:' isomer is indicated to be the nonplanar cyclobutadiene dication (la); the planar form, lb, is indicated to be 7.5 kcal/mol less stable. The second most stable C4Ha' isomer, the methylenecyclopropene dication, is indicated to prefer the perpendicular (2a) over the planar (2b) arrangement by 7 kcal/mol. The "anti van't Hoff" cyclo-(HB)2C=CH2 system (4), isoelectronic with 2, also prefers the perpendicular conformation (4a), and retains the C=C double bond. The linear butatriene dication (3) is the least stable C4Hi' species investigated. The perpendicular (&d) arrangement (3a), permitting double ally1 cationlike conjugation, is preferred over the planar &h form (3b) by 26 kcal/mol. The heat of formation of the most stable form of CdHq' , la, is estimated to be 623-640 kcal/mol. This species should be thermodynamically stable toward dissociation into smaller charged fragments.