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FOURIER transform ion cyclotron resonance spectroscopy

University of British Columbia

Chapter II of this thesis describes the operation of a Fourier Transform Ion Cyclotron Resonance Spectrometer. Included is a detailed discussion of software which was developed to run the spectrometer and analyze the data. An automatic data acquisition system for kinetic experiments is also described. Chapter III contains a short discussion of discrete versus continuous methods of data acquisition and problems with the FT-ICR method which utilizes discrete sampling. Two techniques are discussed which have been found to solve problems associated with a digital system, acquisition by "mixing" and zero-filling. Also, mass calibrations done on the FT-ICR spectrometer are presented. The reactions of some negative ions with esters in the gas phase have been studied by FT-ICR and are discussed in Chapter IV. The reactions of ¹⁸0 labelled methoxide with methyl trifluoroacetate, methyl benzoate, dimethyl carbonate, diethyl carbonate and dipropyl carbonate have been studied. It was found that there is incorporation of ¹⁸0 in product ions of the form RCOO⁻ showing that methoxide attacks esters in the gas phase partially at carbonyl carbon. Product distributions are found to be consistent with two competing mechanisms, B[sub AC]2 and S[sub N]2. Thus it was found that CH₃•0⁻ reacts with C₆H₅COOCH₃- 92% by a B[sub AC]2 type mechanism and 8% by an S[sub N]2 type mechanism. The amount of ¹⁸0 incorporation in product ions was seen to decrease with the presence of β hydrogens, due to the presence of an elimination channel. The reaction of ethoxide with the above named esters was studied and the products are also interpreted in terms of three competing mechanisms, B[sub AC]2, S[sub N]2 and elimination.

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2010-03-03

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http://hdl.handle.net/2429/21408

Chemistry

University of British Columbia

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