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Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing
Published on: March 22, 2019
Naphthol coupling monitored by infrared spectroscopy in the gas phase
1Department of Organic Chemistry, Charles University in Prague, Hlavova 8, 12843 Prague 2, Czech Republic. roithova@natur.cuni.cz
Journal of the American Chemical Society
|December 4, 2009
Summary
Copper(II)-mediated naphthol coupling occurs in gas-phase binuclear clusters. Irradiation triggers the C-C coupling, driven by keto-enol tautomerization, forming binol exothermically.
Area of Science:
- Organometallic Chemistry
- Spectroscopy
- Computational Chemistry
Background:
- Copper-catalyzed coupling reactions are vital in organic synthesis.
- Understanding reaction mechanisms at the molecular level is crucial for catalyst design.
- Gas-phase studies offer unique insights into reaction pathways, free from solvent effects.
Purpose of the Study:
- To elucidate the reaction mechanism of copper(II)-mediated naphthol coupling.
- To investigate the role of TMEDA (N,N,N',N'-tetramethylethylenediamine) in the coupling process.
- To characterize the intermediate species involved in the gas phase.
Main Methods:
- Infrared multiphoton dissociation (IRMPD) spectroscopy was employed to study isolated binuclear clusters.
- Density Functional Theory (DFT) calculations were used to model the reaction pathway and energetics.
- Gas-phase isolation and characterization of reaction intermediates were achieved.
Main Results:
- The coupling reaction proceeds via ad hoc formed binuclear clusters: [(1-H)(2)Cu(2)Cl(TMEDA)(2)](+).
- IRMPD spectra confirmed the presence of uncoupled naphtholate subunits within the cluster.
- Irradiation was identified as the trigger for the C-C coupling reaction.
- Keto-enol tautomerization of the initial product drives the C-C coupling, with binol formation being exothermic (-0.61 eV).
- Analogous C-O and O-O couplings were found to be endothermic.
Conclusions:
- The study reveals a genuine gas-phase copper-mediated naphthol coupling mechanism.
- Binuclear copper clusters and subsequent irradiation are key to initiating C-C bond formation.
- Thermodynamic favorability of keto-enol tautomerization dictates the C-C coupling pathway over C-O or O-O couplings.
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