An Experimental Thermochemical and Theoretical Study of Triquinacene: Definitive Disproof of Its Neutral Homoaromaticity
详细信息 查看全文
- 作者：Sergey P. Verevkin ; Hans-Dieter Beckhaus ; Christoph Rü ; chardt ; Rainer Haag ; Sergei I. Kozhushkov ; Tosja Zywietz ; Armin de Meijere ; Haijun Jiao ; and Paul von Ragué ; Schleyer
- 刊名：Journal of the American Chemical Society
- 出版年：1998
- 出版时间：November 4, 1998
- 年：1998
- 卷：120
- 期：43
- 页码：11130 - 11135
- 全文大小：74K
- 年卷期：v.120,no.43(November 4, 1998)
- ISSN：1520-5126
文摘
The enthalpy of formation (
= 57.51 ± 0.70 kcal/mol) of triquinacene (1), newlydetermined by measuring its energy of combustion in a microcalorimeter, is about 4 kcal/mol higher than thatpreviously reported and corresponds to ab initio and density functional theory computational results. As aconsequence, the previously derived homoaromatic stabilization energy (claimed to be 4.5 kcal/mol) fromenthalpy of hydrogenation measurements is not present in 1. The lack of homoaromaticity in 1 is supportedby evaluation of geometric, energetic, and magnetic criteria. In contrast, the isomerization transition statefrom diademane (5) to 1 is highly aromatic on the basis of the same criteria. The enthalpy of isomerizationof 5 to 1 was experimentally determined by differential scanning calorimetry (DSC) to be -29.4 ± 0.3 kcal/mol (measured at 368.2 K). The enthalpy of activation for this rearrangement as determined from the DSCmeasurements (28.4 ± 0.2 kcal/mol) is 2.5 kcal/mol higher than the value computed at B3LYP/6-311+G**+ZPE.
= 57.51 ± 0.70 kcal/mol) of triquinacene (1), newlydetermined by measuring its energy of combustion in a microcalorimeter, is about 4 kcal/mol higher than thatpreviously reported and corresponds to ab initio and density functional theory computational results. As aconsequence, the previously derived homoaromatic stabilization energy (claimed to be 4.5 kcal/mol) fromenthalpy of hydrogenation measurements is not present in 1. The lack of homoaromaticity in 1 is supportedby evaluation of geometric, energetic, and magnetic criteria. In contrast, the isomerization transition statefrom diademane (5) to 1 is highly aromatic on the basis of the same criteria. The enthalpy of isomerizationof 5 to 1 was experimentally determined by differential scanning calorimetry (DSC) to be -29.4 ± 0.3 kcal/mol (measured at 368.2 K). The enthalpy of activation for this rearrangement as determined from the DSCmeasurements (28.4 ± 0.2 kcal/mol) is 2.5 kcal/mol higher than the value computed at B3LYP/6-311+G**+ZPE.