Interaction of a Weakly Acidic Dinitroaromatic with Alkylamines: Avoiding the Meisenheimer Trap.
Polynitroaromatics are well-known to form anionic s-complexes (Meisenheimer complexes). The formation of such complexes was assumed in the past to explain the blue color of solutions of 2,4-dinitrotoluene (DNT) and amines. However, this work shows that caution is warranted to avoid the hasty misiden...
| Publicado en: | Journal of the American Chemical Society Vol. 133; no. 32; pp. 12858 - 12866 |
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| Autores principales: | , , , |
| Formato: | Artículo |
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American Chemical Society
8/17/2011
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| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=65264489&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 65264489 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 8/17/2011 vid: 133 iid: 32 pid: 997 pub: American Chemical Society artinfo: ui: 65264489 10.1021/ja205156r ppf: 12858 ppct: 8 formats: tig: atl: Interaction of a Weakly Acidic Dinitroaromatic with Alkylamines: Avoiding the Meisenheimer Trap. aug: au: Olson, Eric J. Teng T. Xiong Cramer, Christopher J. Böhlmann, Philippe affil: Department of Chemistry and Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States su: Addition polymerization Complex compounds Dinitrotoluenes Density functionals Aromaticity sug: subj: Addition polymerization Complex compounds Dinitrotoluenes Density functionals Aromaticity ab: Polynitroaromatics are well-known to form anionic s-complexes (Meisenheimer complexes). The formation of such complexes was assumed in the past to explain the blue color of solutions of 2,4-dinitrotoluene (DNT) and amines. However, this work shows that caution is warranted to avoid the hasty misidentification of Meisenheimer complexes. 1H NMR spectra exhibit no significant shifts in the positions of the DNT protons, indicating that the majority of DNT species in solutions of DNT and amines retain their aromaticity. Density functional calculations on DNT-ethylamine complexes suggest that Meisenheimer complexes are sufficiently high in free energy so that they make up only a very small fraction of the full equilibrium population. While principal component analysis of the UV/vis spectra of the DNT-amine solutions reveals that only one absorbing species of significant concentration is formed, quantitative fits of Job's plots show that 1:1 association of DNT with the amines alone cannot explain the visible absorption spectra. Instead, the Job's plots can be accurately interpreted by deprotonation of DNT, with the amines acting as bases. The deprotonation equilibria lie far on the side of the unreacted DNT, preventing the detection by NMR of the deprotonated minority species that gives the solutions their strong blue color. The analysis of systems with DNT and n-butylamine, diethylamine, triethylamine, or benzylamine provides a consistent pK of DNT in dimethyl sulfoxide of 15.3 ± 0.2. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2011 holdings: @attributes: islocal: N |
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