3-isoamyl-ethyl-amino-6-methyl-7-anilino fluoran(S-205)의 열 변색 현상에 관한 열역학적 연구 = Thermodynamic Study on the Thermochromism of 3-isoamyl-ethyl-amino-6-methyl-7-anilino fluoran(S-205)

다국어 초록 (Multilingual Abstract)

Absorption spetra of thermochromic of 3-isoamylethyl-amino-6-methyl-7-anilino fluoran(S-205) was investigated. The S-205 exists as a colorless lactone in aprotic solvents. However, the S-205 exists in the form of an equilibrium mixture of a colored zwitter-ion and a colorless lactone in protic solvents.
In order to understand the interaction between the S-205 and the solvent, absorption spectra of the S-205 in various solvents were measured. The systematic increase of the λ_max of the S-205 correlate with the solvent polarity of the solvent in protic solvent and aprotic solvent.
The enthalpy changes of the S-205 has also been investigated. From the variation of absorbance with temperature, the standard enthalpy changes △H_0 the equilibrium between the lactone and the zwitter-ion in various solvents have been determined. The standard enthalpy change △H_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.