Pyrolysis of 1-methyl-2-phenyldiazene

Cook, Arthur M. (1988) Pyrolysis of 1-methyl-2-phenyldiazene. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (19MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

The question of whether diazenes lose nitrogen through one or two bond scission has been a subject of study for over fifty years. Using recently available data on azobenzene and previously published Arrhenius parameters for azomethane a kinetic approach was taken to this problem using 1-methyl-2-phenyldiazene. -- In the first part of this thesis the synthesis and purification of 1-methyl-2-phenyldiazene is described. -- The next section deals with the construction of the vacuum line and its associated apparatus. The problems with the original design are discussed and modifications which were made to the line are outlined. -- In the results section are presented the definition of the rate constant for nitrogen formation and a table of products of reaction, which, with the associated appendices show how the products were identified and measured. The yield-time, order, and Arrhenius plots are then presented for both the unpacked and packed reaction vessels as well as results for experiments in which propene was present. -- A summary of the observations is first given in the discussion section. The possibility of direct decomposition of 1-methyl-2-phenyldiazene with no contribution from the chain is next discussed, along with a consideration of the trans to cis isomerization. Both are shown to be implausible, using aguments based on the results obtained. -- Based on the effect of propene, the orders of reaction, and the values of the Arrhenius parameters, two mechanisms are then proposed. The simple one is written to show that nitrogen may be formed by a chain reaction as well as by simple fission of 1-methyl-2-phenyldiazene. It is solved to show that it is first order with respect to nitrogen formation. The second mechanism accounts for the products of reaction and also adds a second chain to the pyrolysis. Speculation on the formation and reaction of diradicals is then made. The complete mechanism is then solved to show that it too is first order with respect to nitrogen formation. -- Possible Arrhenius parameters of the simple fission of 1-methyl-2-phenyldiazene are then proposed based on the propene results. These parameters agree quite well with what Forst and Rice obtained for azomethane and suggest one bond scission of 1-methyl-2-phenyldiazene. -- Speculation as to why, in the initial series of propene experiments, no inhibition of the rate of nitrogen formation appeared is then made. The possible role of phenylhydrazone is also considered. -- Finally, the erratic behavior of the reaction after the initial series of propene experiments is commented on, and further directions for the study of this reaction are presented.

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