This thesis describes the synthesis and characterization of triaminocyclopropenium, [C3(NR2)3]+, ionic liquids. A range of triaminocyclopropenium salts were prepared: D3h, C3h, C2v and Cs symmetric cations with a variety of substituents. D3h and C3h symmetric cations were prepared from pentachlorocyclopropane and dialkylamines, whereas a variety of methods were investigated for C2v and Cs symmetric cations, with the most versatile synthesis involving the alkylation of bis(dialkylamino)cyclopropenone followed by reaction with dialkylamine. Metathesis with a range of common ionic liquid anions was carried out to facilitate comparisons to other common classes of ionic liquids.
The triaminocyclopropenium salts were characterized by standard techniques (1H-, 13C{1H}-NMR, ES+ MS, microanalysis) as well as particular physicochemical properties
relevant to ionic liquids. The thermal behaviour was examined with DSC, with the majority of salts being liquid at room temperature. The viscosity of triaminocyclopropenium ionic liquids was similar to other classes of ionic liquid cations, in the range of 58.4 to 554 mPa s at 20 °C. This is despite the generally large size of the cations investigated, which also causes the conductivity to be lower.
Triaminocyclopropenium ionic liquids show good ionicity, more than other common classes of ionic liquid cation, which is likely due to the relatively electron-rich nature of the cation. The thermal, electrochemical and chemical stability of
triaminocyclopropenium ionic liquids was accessed. Good thermal stabilities were observed, with onset temperatures of 339 to 413 °C. The electrochemical window of [C3(NEt2)3]TFSA is 3.6 V, this is low due to the easy oxidation of the cation. The
chemical stability is good under acidic, weakly-basic, weakly-nucleophilic, reducing and weakly-oxidising conditions, however, the cations are unstable to the strong nucleophile/base hydroxide. Triaminocyclopropenium ionic liquids showed a full range of solubility and miscibility: from fully miscible in water to fully miscible in hexane.
A preliminary investigation of ionic liquid fluorides was carried out. While stable ionic liquids with naked fluorides were not obtained, ionic liquids with strongly-bound solvate molecules (ethanol and acetic acid) were seeen, and their viscosity, conductivity and density were measured. The attachment of hydroxyl functional groups to triaminocyclopropenium cations was seen to improve the stability of ionic liquid fluorides, although at the cost of high viscosity.
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/7637 |
| Date | January 2013 |
| Creators | Walst, Kelvin John |
| Publisher | University of Canterbury. Chemistry |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Kelvin John Walst, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
| Relation | NZCU |
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