| Co-Investigator(Kenkyū-buntansha) |
ICHIKAWA Junji Kyushu University, Institute of Advanced Material Study, Assistant, 機能物質科学研究所, 助手 (70184611)
SONODA Takaaki Kyushu University, Institute of Advanced Material Study, Associate Professor, 機能物質科学研究所, 助教授 (90108770)
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| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1989: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1988: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
1. On the purpose of elucidating the mechanism by which thermal Z/E isomerization of aromatic azo compounds is suppressed by fluoro-substituents, a series of fluoro-substituted phenylazo derivatives were prepared systematically in respect of the substituted positions, and methyl-, chloro-, trifluoro- methyl-, and nitro-substituted ones were also done in a similar manner as the reference compounds for comparisons of the substituent kinetic effect on the thermal Z/E isomerization. Most of them were prepared by a facile one-pot method where diazotization and in situ coupling were carried out in a single reaction vessel by use of novel anion-catalyzed phase-transfer catalysis (PTC), and rest of them to which the PTC method was not applicable, by the conventional method. N,N-Dimethylaniline, N-ethylcarbazole, 1-methoxynaphthalene, and anisole were used as the coupler components.
2. UV and visible absorption spectra of the aromatic azo compounds were measured in sovents of varying polarities
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such as hexane, dichloromethane, and ethanol. The first-order rate constants of the thermal Z/E isomerization and the half-life times of the Z-isomers were photometrically determined. Also the activation parameters, DELTAH<thermodynamics> and DELTAS<thermodynamics>, were determined from the rate constants obtained in variable temperature experiment
3. The following observations are obtained concerning the thermal Z/E isomerization of substituted phenylazo compounds: (1) Solvent-polarity causes far less kinetic effects so that the inversional mechanism is operative. (2) Fluoro-substituents on the ortho position, especially on both ortho positions, suppress remarkably the Z/E isomerization, while those on the meta and para positions promote the same reaction. (3) Similar retardation effects are caused by ortho chloro- and methyl substituents, which indicates that such kinetic effect is due to destabilization of the inversional transition state by electron-repulsive ortho-substituents. (4) Plots of the activation parameters of 2,6-disubstituted phenylazo compounds, especially corresponding difluoro derivatives are far deviated from the general DELTAH<thermodynamics>-DELTAS<thermodynamics> compensation relationships observed in ordinary azo dyes. (5) The kinetic effects of the ortho substituents on the Z/E isomerization via the rotational transition state exhibit different behaviors from those of the inversional isomerizatio Less
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