Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/3323
Title: Some new approaches to alkene epoxidation with manganese catalyst
Authors: Ho, Kam-piu
Keywords: Hong Kong Polytechnic University -- Dissertations
Alkenes -- Oxidation
Epoxy compounds
Catalysis
Issue Date: 2006
Publisher: The Hong Kong Polytechnic University
Abstract: Epoxides are important starting materials in organic synthesis, as they can be easily transformed into other useful functionalities. Although there are many existing routes to prepare epoxides, many of these processes involve toxic chemicals and volatile organic solvents that cause pollution to the environment. The objective of this study is to develop some new approaches for alkene epoxidation that can minimize the use of toxic chemicals and solvents in the synthetic process. Manganese catalysts are chosen in this study because they are relatively non-toxic and many manganese compounds are known to be good catalysts for epoxidation. In the first part of the thesis, hydrogen peroxide (H₂O₂) was generated in aqueous bicarbonate solutions electrochemically for the in-situ epoxidation of alkenes. Dioxygen (O₂) was directly reduced at the cathode to generate hydrogen peroxide, while epoxide was formed in-situ with a catalytic amount of manganese(II) sulfate (MnSO₄). Water-soluble alkenes were epoxidized with excellent yields and high efficiencies. The system can be adapted for the epoxidation of lipophilic alkenes in a tert-butanol/water/Mn²⁺/HCO₃⁻ mixture. In the second part of the thesis, ionic liquids (ILs) were employed as reaction media to generate hydrogen peroxide electrochemically for the epoxidation of alkenes. Ionic liquids are non-volatile and highly conductive solvents in which hydrogen peroxide could be generated by electrochemical reduction of dioxygen in the presence of suitable amount of water. The active oxidant peroxymonocarbonate (HCO₄⁻) was generated in the hydrogen peroxide/ionic liquid mixture by purging with carbon dioxide. Lipophilic alkenes were effectively epoxidized with the assistance of a catalytic amount of manganese(II) sulfate. The ionic liquids can be reused without any diminution in the efficiency of electrosynthesis and catalysis. In the third part of the thesis, a catalytic system based on simple manganese salt was developed for the efficient epoxidation of terminal aliphatic alkenes with peracetic acid. Terminal aliphatic alkenes are a challenging class of substrates in epoxidation because of their poor nucleophilicity. We found that terminal aliphatic alkenes are efficiently and selectively epoxidized at ambient temperature by peracetic acid/Mn²⁺/NH₄HCO₃in acetonitrile/water mixture with low catalyst loading. The reaction is stereospecific with retention of the cis/trans configuration of the alkenes in the epoxide products.
Description: xii, 236 leaves : ill. ; 30 cm.
PolyU Library Call No.: [THS] LG51 .H577P ABCT 2006 Ho
URI: http://hdl.handle.net/10397/3323
Rights: All rights reserved.
Appears in Collections:Thesis

Files in This Item:
File Description SizeFormat 
b19579858_link.htmFor PolyU Users 162 BHTMLView/Open
b19579858_ir.pdfFor All Users (Non-printable) 2.75 MBAdobe PDFView/Open
Show full item record

Page view(s)

580
Last Week
2
Last month
Checked on Feb 26, 2017

Download(s)

498
Checked on Feb 26, 2017

Google ScholarTM

Check



Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.