title: Determination by ultraviolet absorption spectrometry and theoretical calculation of dissociation constant of 1,2,3,9-tetrahydro-4H-carbazol-4-one.
abstract: The dissociation constant of 1,2,3,9-tetrahydro-4H-carbazol-4-one was determined by ultraviolet absorption spectrometry method based on the absorption spectra of 1,2,3,9-tetrahydro-4H-carbazol-4-one at different pH in ethanol-water mixed solvents. The results show that the pK(b) was a good linear function of the volume fraction of ethanol in the concentration range studied. The dissociation constant of 1, 2, 3,9-tetrahydro-4H-carbazol-4-one in water were determined by extrapolation to be 14.04 under the condition of this experiment. The accurate pK(b) calculations of 1,2,3,9-tetrahydro-4H-carbazol-4-one have been investigated using the combination of the extended clusters-continuum model with the polarizable continuum solvation model (PCM). The calculations are performed at the B3LYP/6-31G levels. The formation of molecular clusters by means of the 1,2,3,9-tetrahydro-4H-carbazol-4-one wrapped up with water molecules leads to the weakness of the interaction between the polar solvents and the 1,2,3,9-tetrahydro-4H-carbazol-4-one, hence, the accuracy of pK(b) has been enhanced. The dissociation constant of 1,2,3,9-tetrahydro-4H-carbazol-4-one in water were calculated to be 14.10 and agreed well with experimental data.
authors.affiliation: College of Chemistry, Qufu Normal University, Shandong, Qufu, 273165, PR China. zhshf999@sina.com
authors.forename: Shufang
authors.initials: S
authors.lastname: Zhang
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Zhang
authors.forename: Ke
authors.initials: K
authors.lastname: Tang
authors.forename: Zhengyu
authors.initials: Z
authors.lastname: Zhou
mesh_terms: D002227:Carbazoles / Q000737:chemistry*; D003198:Computer Simulation; D000431:Ethanol / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D011789:Quantum Theory; D012995:Solubility; D012997:Solvents / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: C513019:1,2,3,9-tetrahydro-4H-carbazol-4-one; D002227:Carbazoles; D012997:Solvents; D014867:Water; D000431:Ethanol