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KMID : 0974620020200020545
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Bulletin of Dongnam Health University
2002 Volume.20 No. 2 p.545 ~ p.553
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A Study on the Thermochromism of PSd-150 (3-cyclohexyl-methyl-amino-6-methyl-7-anilino-fluoran) Dyes
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Choi Jae-Gu
Kim Jong-Gyu
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Abstract
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The thermochromism of PSD-150has been examined. The PSD-150 exists as a colorless lactone in aprotic solvents. However, the PSD-150 exists as the form of an equilibrium mixture of a colored zwitter-ion and a colorless lactone in protic solvents. When an acid is added to the solution, the PSD-150 exists as an equilibrium mixture a colorless lactone and a colored cation even in aprotic solvents. In order to understand the interaction between the PSD-150 and the solvent, absorption spectra of the PSD-150 in various solvents were measured. The systematic increase of the λ_(max) of the PSD-150 correlates with the hydrogen-bond donor ability of the solvent in neutral solution. The thermodynamic parameters of the PSD-150 have also been investigated. From the variation of absorbance with temperature, the standard enthalpy changes ΔH^0 of the equilibrium between the lactone and the zwitter-ion in various solvents have been determined. The standard enthalpy change ΔH^0 is approximately -7 kJ/㏖ in protic solvents. In acidic solution, the standard enthalpy change is measured to be to zero in protic solvents within the experimental error. When the carboxylic group is protonated in acidic solution, a poor interaction between the dye and the solvent is expected.
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