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||Size||Format||MacDonald2011.doc||one year restriction||25.87 MB||Microsoft Word||MacDonald2011.pdf||one year restriction||4.99 MB||Adobe PDF|
|Title: ||Novel routes to Heterocyclic Azo compounds|
|Authors: ||MacDonald, Ranald John|
|Supervisor(s): ||McNab, Hamish|
|Issue Date: ||23-Nov-2011|
|Publisher: ||The University of Edinburgh|
|Abstract: ||The potential use of electron-deficient heterocyclic azo compounds as inkjet dyes was
explored. 2-Nitrosopyridine could be used to form a series of azo compounds via the
Mills’ reaction with electron-rich aromatic amines. Conditions for this process were
optimised by varying solvent and pH. In the presence of ethers, 2-nitrosopyridine is
quickly reduced to azoxypyridine. This reaction follows first order kinetics; diethyl
and diisopropyl ether react at similar rates, whereas cyclic ethers such as THF are far
slower. Organic bases such as Hunigs base were also found to promote formation of
azoxypyridine. The mechanism of this reduction was studied. The electrochemistry of
2-nitrosopyridine and azoxypyridine was also explored.
Using the optimised conditions for the Mills’ reaction, 2-nitrosopyridine not only
reacts with electron-rich amines but also electron-deficient examples. The series was
also expanded to include other heterocycles as well as pyridine via the corresponding
heterocyclic nitroso compound. Other nitroso compounds prepared were 1-
nitrosoisoquinoline, 2-nitrosopyrazine, 4-nitrosopyrimidine and 2-nitrosopyrimidine.
The absorption maxima of azo compounds prepared from these precursors were found
to correlate with the values for the corresponding azobenzenes.
2-Nitrosopyridine and 2-nitrosopyrimidine react with diamines to give monoazo
products. These in turn could be diazotised and coupled with various components to
give either bisazo or trisazo compounds. These dyes were tested for their ozone and
light fastness properties. The bisazo examples were found to have good ozone fastness
but poor light fastness. The pyrimidine examples only showed a slight improvement in
ozone and light fastness compared to their pyridine analogue.
2,3-Phthalocyanines are important components in cyan dyes. New routes to precursors
of these compounds were explored using flash vacuum pyrolysis (FVP).|
|Sponsor(s): ||Engineering and Physical Sciences Research Council (EPSRC)|
|Appears in Collections:||Chemistry thesis and dissertation collection|
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