title: Tautomeric equilibrium of ethyl acetoacetate in compressed CO2 + ethanol and CO2 + methanol mixtures.
abstract: Tautomerism equilibrium of ethyl acetoacetate (EAA) in compressed CO2 + methanol and CO2 + ethanol mixtures was studied by UV-Vis spectroscopy at 308.15 K and different pressures. The volume expansion coefficient (alpha) of the solvents at different pressures was also determined. The relative permittivity (epsilon) of CO2 + methanol and CO2 + ethanol mixtures at different conditions was calculated using the Kc and Onsager solvent parameter. The equilibrium constant (Kc) of EAA in the binary mixtures increases considerably with increasing pressure or volume expansion coefficient. The relative permittivity or the polarity of the binary mixtures decreases sharply with increasing volume expansion coefficient in the range of 0 < alpha < 1.5. However, as the volume expansion coefficient exceeds 1.5, the relative permittivity decreases slowly. In other words, the dissolution of CO2 in the polar solvents can reduce the polarity of the solvents significantly in the low volume expansion coefficient range, and the polarity of the solution is not sensitive to the volume expansion coefficient as its value is large enough. The difference in polarity of the two solvents reduces with increasing pressure and becomes negligible after volume expansion coefficient exceeds about 2.5.
authors.affiliation: Center for Molecular Science, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100080, PR China.
authors.forename: Zhonghao
authors.initials: Z
authors.lastname: Li
authors.forename: Tiancheng
authors.initials: T
authors.lastname: Mu
authors.forename: Tao
authors.initials: T
authors.lastname: Jiang
authors.forename: Jimin
authors.initials: J
authors.lastname: Du
authors.forename: Guoying
authors.initials: G
authors.lastname: Zhao
authors.forename: Jianling
authors.initials: J
authors.lastname: Zhang
authors.forename: Buxing
authors.initials: B
authors.lastname: Han
authors.forename: Ying
authors.initials: Y
authors.lastname: Huang
mesh_terms: D000090:Acetoacetates / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry*; D007700:Kinetics; D000432:Methanol / Q000737:chemistry*; D008956:Models, Chemical; D011312:Pressure; D012997:Solvents; D013053:Spectrophotometry / Q000379:methods*; D013696:Temperature; D013816:Thermodynamics; D014466:Ultraviolet Rays
chemical_list: D000090:Acetoacetates; D012997:Solvents; D002245:Carbon Dioxide; D000431:Ethanol; C024840:ethyl acetoacetate; D000432:Methanol