OBD-2의 열 변색 현상에 관한 열역학적 연구 = Thermodynamic Study on the Thermochromism of OBD-2

다국어 초록 (Multilingual Abstract)

The termochromism of OBD-2 has been examined. The OBD-2 exists as a colorless lactone in aprotic solvents. However, the OBD-2 exists in the form of an equilibrium imxture of a colored zwitter-ion and a colorless lactone in protic solvents. When an acid is added to the solution, the OBD-2 exists and equilibrium mixture as a colorless lactone and a colored cation even in aprotic solvents.
In order to understand the interaction between the OBD-2 and the solvent, absorption spectra of the OBD-2 in various solvents were measured. The systematic increase of the λ_max of the OBD-2 correlate with the hydrogen-bond donor ability of the solvent in neutral solution.
The thermodynamic parameters of the OBD-2 has also been investigated. From the variation of absorbance with temperature, the standard enthalpy changes △H^0 of 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/mol 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.