The Palladium(II)-catalyzed homogeneous oxidation of 1-hexene in methanolic medium has been studied, copper(II) chloride being used as cocatalyst. Aspects of the kinetics, mechanism and product composition were investigated in several series of oxidations involving variation of hexene concentration, oxygen partial pressure, Cu(II): Pd(II) ratio and concentration and temperature. The progress of the reaction was studied in the course of periodic sampling runs. Reaction products were identified by gas chromatography, and verified by means of GC/mass spectrometry. The expected product of 1-hexene oxidation was 2-hexeanone: however, 3-hexanone occurs as a major coproduct, arising from concurrent Pd(II)-catalyzed isomerization of 1-hexene to 2-hexene. Isomerization is inhibited by excess copper(II) chloride. The overall oxidation is generally consistent with P.M. Henry’s mechanism for Pd(II)-catalyzed alkene oxidation, the rate-limiting step being the π-to σ-rearrangement of the Pd(hexane) complex. The corresponding ketals (2,2-dimethoxyhexane and 3,3-dimethoxyhexane) were also found. Free hexanal was not detected in any oxidation product mixtures; when produced it was found as the dimethyl acetal. Chlorination products were not observed. A surprisingly sharp rate maximum was observed when copper(II) chloride concentration was varied. Two kinetic regions were found to occur in virtually all oxidations. An explanation is proposed for this behavior.
| Identifer | oai:union.ndltd.org:WKU/oai:digitalcommons.wku.edu:theses-2781 |
| Date | 01 May 1992 |
| Creators | Kirova, Margarita |
| Publisher | TopSCHOLAR® |
| Source Sets | Western Kentucky University Theses |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Masters Theses & Specialist Projects |
Page generated in 0.0022 seconds