FIRST AND SECOND IONIZATION ENERGIES OF 1,3,5-TRIMETHYLBENZENE AND 2,4,6-TRIMETHYLPYRIDINE

被引：9

作者：

Milko, Petr ^{[1
]}

Schroeder, Detlef ^{[1
]}

Lemr, Karel ^{[2
]}

Zabka, Jan ^{[3
]}

Alcaraz, Christian ^{[4
,5
]}

Roithova, Jana ^{[1
,6
]}

机构：

[1] Acad Sci Czech Republ, Inst Organ Chem & Biochem, CR-16610 Prague 6, Czech Republic

[2] Palacky Univ, Dept Analyt Chem, Olomouc 77146, Czech Republic

[3] Acad Sci Czech Republ, J Heyrovsky Inst Phys Chem, Prague 18300 8, Czech Republic

[4] Ctr Univ Paris Sud, Chim Phys Lab, UMR 8000, F-91405 Orsay, France

[5] Synchrotron SOLEIL, F-91192 Gif Sur Yvette, France

[6] Charles Univ Prague, Fac Sci, Dept Organ Chem, Prague 12840 2, Czech Republic

来源：

COLLECTION OF CZECHOSLOVAK CHEMICAL COMMUNICATIONS | 2009年 / 74卷 / 01期

关键词：

Ionization energy; Isodesmic reactions; Jahn-Teller effect; Mass spectrometry; Synchrotron; Substituent effect; Arenes; BOND; DICATIONS;

D O I：

10.1135/cccc2008166

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

The first and second ionization energies of trimethyl substituted analogs of benzene and pyridine are determined by means of mass spectrometry in conjunction with synchrotron radiation. The first ionization energy of 1,3,5-trimethylbenzene amounts to (8.38 +/- 0.05) eV and the second ionization energy to (22.8 +/- 0.1) eV. The first ionization energy of 2,4,6-trimethylpyridine is determined as (8.65 +/- 0.05) eV and the second ionization energy as (23.0 +/- 0.1) eV. The ionization energies are compared with those of unsubstituted benzene and pyridine and the effects of the methyl groups are evaluated by means of isodesmic reactions. As expected, it is found that the electron-donating effect of the methyl groups stabilizes neutral pyridine and doubly charged pyridine more than neutral benzene and doubly charged benzene, respectively. Surprisingly, the opposite effect is found for the radical cations, which is ascribed to the unfavorable degenerate electronic structure of benzene radical-cation, which disappears upon the methyl substitution.

引用

页码：101 / 114

页数：14

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