Properties of the Diazo Group (-N=N-) Modified by Oxidation

Krzysztof Ejsmont 1Tadeusz M. Krygowski 2Michal K. Cyranski 2Beata T. Stepien 2

1. Opole University, Institute of Chemistry (OU), Oleska 48, Opole 45-052, Poland
2. Warsaw University, Faculty of Chemistry, Pasteura 1, Warszawa 02-093, Poland

Abstract

The oxidation of the diazo group (-N=N-) leads to the azoxy and azodioxy compounds [1] as shown below:

kejsmont.jpg

The functional groups -NN(O)-, -(O)NN- and -N(O)N(O)- differ in their properties as substituents. To quantify the extent of the changes of electronic structure of the diazo group upon oxidation we have applied a method of estimation the resonance substituent constance (σ- values), which based on the variation of the aromatic character of 8-substituted heptafulvene [2]. While the electronic character of the -NN(O)-, -(O)NN- groups is rather similar to the diazo group (σ- = 1.08, 1.00 and 1.02, respectively), the azodioxy group is significantly more electron-accepting substituent (with σ- = 1.20). The analysis is based on the ab initio optimized geometries at DFT B3LYP/6-311+G** level of theory. Since the diazo- and azoxy- groups are isoelectronic with the nitroso and nitro groups, the comparative study of their influence on π-electron delocalization of benzene was performed.

[1] A. F. Wells, Structural Inorganic Chemistry, Oxford University Press, 1984, ch. 18.


[2] a) B. T. Stępień, T. M. Krygowski, M. K. Cyrański, J. Org. Chem. 2002, 67, 5987. b) B. T. Stępień, T. M. Krygowski, M. K. Cyrański, Chem. Phys. Lett. 2001, 350, 537. c) T. M. Krygowski, B. T. Stępień, Chem. Rev. 2005, 105, 3482.

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Presentation: poster at 18th Conference on Physical Organic Chemistry, Posters, by Krzysztof Ejsmont
See On-line Journal of 18th Conference on Physical Organic Chemistry

Submitted: 2006-06-06 12:32
Revised:   2009-06-07 00:44
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