Edinburgh Research Archive >
Chemistry, School of >
Chemistry thesis and dissertation collection >
Please use this identifier to cite or link to this item:
|Title: ||Gas-phase electron diffraction studies of unstable molecules|
|Authors: ||Noble-Eddy, Robert|
|Supervisor(s): ||Masters, Sarah|
|Issue Date: ||2009|
|Publisher: ||The University of Edinburgh|
|Abstract: ||Gas-phase electron diffraction (GED) is the only viable technique for the accurate
structural study of gas-phase molecules that contain more than ~10 atoms.
Recent advances in Edinburgh have made it possible to study larger, more
complex, stable molecules using the SARACEN method. This thesis is concerned
with obtaining the structures of unstable species, using both standard GED
techniques and by developing a new method in which
ash vacuum pyrolysis
is used to generate short-lived species in situ.
In the first part of this thesis nine primary phosphines (R-PH2) with different
substituents (R = methyl, vinyl, ethynyl, allenyl, allyl, propargyl, phenyl, benzyl
and chloromethyl) are studied by GED. Vinylarsine and vinyldichloroarsine are
also studied. Primary phosphines and arsines appear infrequently in the literature
owing to their toxicity and high reactivity, especially of the unsaturated systems.
The conformational behaviour in these molecules and trends throughout the series
are rationalised. As appropriate, comparisons are made to analogous amines and
the differences found are discussed.
Tertiary phosphines (R3P) are routinely protected by complexation with borane
(BH3) and it has been proposed that this technique could be extended to primary
phosphines. As an extension of the initial investigation, the GED study of
methylphosphine-borane offers an insight into structural changes that occur upon
complexation, although attempts to study larger phosphine-borane complexes by
GED proved dificult. The structures and bonding trends in a series of phosphineborane
adducts are discussed, mainly using the results of ab initio calculations.
The second part of the thesis details the implementation of a new, very high temperature nozzle, which allows the generation of short-lived species by
pyrolysis. The workings of this nozzle are discussed and the study of the structure
of ketene, generated from three different precursors, is detailed. The benzyl
radical has also been studied, and a preliminary GED structure is presented. As a
result of this work the molecular structures of Meldrum's acid and dibenzylsulfone
are also presented, having been determined in the gas phase for the first time.|
|Keywords: ||gas-phase electron diffraction|
flash vacuum pyrolysis
|Appears in Collections:||Chemistry thesis and dissertation collection|
Items in ERA are protected by copyright, with all rights reserved, unless otherwise indicated.