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Organic synthesis in ionic liquids

Ryan, Robert (2003) Organic synthesis in ionic liquids. Master of Science thesis, Dublin City University.

Solvents play an important role in organic chemistry. Most reactions must be carried out in organic solvents, thus chemists have to deal with large volumes of solvents everyday. Solvents are highly damaging chemicals for two main reasons; (a) they are used on a large scale and (b) they are volatile which makes storage and handling difficult. For environmental protection and reduction of damage to humans, clean technologies have become a major concern throughout both industry and academia. Therefore, the search for the replacement of damaging solvents has become a high priority. Based on such an idea, reactions involving the room temperature and moisture stable 1,3- dialkylimidazolium ionic liquids, have been carried out in an effort to replace the common bench solvents. They are a new type of solvent with attractive properties allowing for their use as both solvent and catalyst in some cases. Therefore, throughout this project the ambient temperature 1,3-dialkylimidazolium ionic liquid was employed firstly for the reduction of simple aldehydes and ketones. In the exploration of these ionic liquids as possible replacements for classical organic solvents, we discovered that the reduction of aldehydes and ketones with sodium borohydride in [bmim]PF6 can be achieved. The ionic liquid can be recycled, and in some cases the product alcohol may be distilled directly from the ionic liquid eliminating classical organic solvents entirely. Secondly, free radical addition reactions using tributyltin hydride, a variety of alkenes and alkyl halides were carried out in the ionic liquids [bmim]BF4 and [bmim]PF6. The reactions using tributyltin hydride were carried out under a number of experimental conditions but the toxicity of the tin by-products produced was a major concern. The ionic liquid was capable of dissolving all reactants and extraction of the products was efficient but the tin by-products proved extremely difficult to remove. (Tris)trimethylsilylsilane was then used in an effort to remove the toxicity and by-product problems. The hydrosilylated product was formed but the target compound was not synthesised. The use of the ionic liquid in these radical reactions, although not a complete success, the hydrosilylated product was formed which suggests that the ionic liquid did stabilise radicals formed. Finally, a novel type of ionic liquid was synthesised and investigated. These compounds were based on 1-vinylimidazole and the synthesis was very efficient and easily carried out. A series of 1-vinyl-3-alkyl-imidazolium bromide, tetrafluoroborate and hexafluorophosphate compounds were synthesised. It was hoped that the vinyl group of these ionic liquids could be used in a Diels-Alder synthesis using a variety of dienes.
Item Type:Thesis (Master of Science)
Date of Award:2003
Supervisor(s):Howarth, Joshua and James, Paraic
Uncontrolled Keywords:Ionic solutions; Reduction (Chemistry); Addition reactions
Subjects:Physical Sciences > Organic chemistry
Physical Sciences > Chemistry
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Science and Health > School of Chemical Sciences
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 License. View License
ID Code:18202
Deposited On:24 May 2013 13:13 by Celine Campbell . Last Modified 24 May 2013 13:13

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