Browsing by Author "Kao, DY"

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A consistent determination of the dimerization constants of the self-association of 2,2-dimethyl-3-ethyl-3-pentanol in carbon tetrachloride from its infrared spectral data
(2005-12-01)
Kao, DY
;
Shu, WT
;
Chen, JS
;
應用化學系
;
Department of Applied Chemistry
Two equations of linear type (Eqs. 10 and 17 in the text) have been derived to analyze the IR data to determine the dimerization constant consistently. Equation 10 is to be used to fit the integrated absorbances of the monomer band to obtain the molar monomer absorptivity, epsilon(m), and dimerization constant, K; Eq. 17 is to be used to fit the integrated absorbances of the dimer bands to obtain the molar dimer absorptivity, epsilon(d), and dimerization constant, K. Thus the same dimerization constant can be independently determined either from the monomer band or from the dimer band. The discrepancy between the two determined values Provides an assessment of the consistency of determination. The monomer-dimer self-association of 2,2-dimethyl-3-ethyl-3-pentanol in the solvent of carbon tetrachloride was chosen to demonstrate the utility of these two equations.
Accurate determination of dimerization constants from IR study of monomer-dimer self-association: 3-ethyl-2-methyl-3-pentanol in carbon tetrachloride as an example
(2004-10-01)
Chen, JS
;
Kao, DY
;
應用化學系
;
Department of Applied Chemistry
The monomer-dimer self-association of 3-2-methyl-pentanol in CCl4 at four different temperatures has been studied using IR spectroscopy. The spectral band of the OH fundamental stretching for a free monomer and that for a hydrogen-bonded dimer were resolved, and their respective integrated absorbances were calculated. The integrated absorbances of the monomer band for various concentrations at a given temperature were then employed based on Eq. 9 to obtain the molar absorptivity of the monomer band and the dimerization constant at that temperature. Similarly, those of the dimer band were employed based on Eq. 13 to determine the molar absorptivity of the dimer band and the dimerization constant at that temperature. Since the same dimerization constant can be determined independently either from the monomer band or from the dimer band, the discrepancy between the two determined values can serve as a criterion of the goodness of the determination. The standard enthalpy and entropy of the dimerization were also obtained from a van't Hoff plot for dimerization constants at different temperatures.
Graphical method for the determination of the complex NMR shift and equilibrium constant for a hetero-association accompanying self-associations
(1997-08-01)
Lin, CC
;
Fang, CY
;
Kao, DY
;
Chen, JS
;
應用化學系
We describe a novel graphical method which, in conjunction with the previously proposed graphical determination of mono;ner shift, dimer shift, and dimerization constant for self-association, allows us to determine the complex shift and equilibrium constant for a hetero-association, A + B reversible arrow AB, accompanying self-associations, A + A reversible arrow A(2), and B + B reversible arrow B-2. The merit of the new method includes the removal of the restrictions imposed on the conventional Benesi-Hildebrand (B-H) plot: (1) that the concentration of one component must be much less than that of the other; (2) that there be no accompanying self-association, The simultaneous equilibrium of the self-association of 2-pyrrolidone (A) and that of 4-methyl-alpha-pyrrolidone (B) and the hetero-association between A and B in acetonitrile-d(3) at 25 degrees C is studied. The inappropriateness of the B-H plot in dealing with this case is also pointed out.
Graphical method for the determination of the complex NMR shift and equilibrium constant for a hetero-association accompanying self-associations
(1997-08-01)
Lin, CC
;
Fang, CY
;
Kao, DY
;
Chen, JS
;
交大名義發表
We describe a novel graphical method which, in conjunction with the previously proposed graphical determination of mono;ner shift, dimer shift, and dimerization constant for self-association, allows us to determine the complex shift and equilibrium constant for a hetero-association, A + B reversible arrow AB, accompanying self-associations, A + A reversible arrow A(2), and B + B reversible arrow B-2. The merit of the new method includes the removal of the restrictions imposed on the conventional Benesi-Hildebrand (B-H) plot: (1) that the concentration of one component must be much less than that of the other; (2) that there be no accompanying self-association, The simultaneous equilibrium of the self-association of 2-pyrrolidone (A) and that of 4-methyl-alpha-pyrrolidone (B) and the hetero-association between A and B in acetonitrile-d(3) at 25 degrees C is studied. The inappropriateness of the B-H plot in dealing with this case is also pointed out.
New approach to IR study of monomer-dimer self-association: 2,2-dimethyl-3-ethyl-3-pentanol in tetrachloroethylene as an example
(2004-08-01)
Chen, JS
;
Wu, CC
;
Kao, DY
;
應用化學系
;
Department of Applied Chemistry
The dimerization of 2,2-dimethyl-3-ethyl-3-pentanol in tetrachloroethylene in the diluted region has been studied at four temperatures by IR spectroscopy. The aforementioned solute compound is chosen because self-association beyond dimerization is hampered by the steric hindrance generated by the bulky sidechains. The integrated absorbances of the monomer bands were treated based on Eq. (9) to obtain its molar absorptivity and dimerization constant. The same dimerization constant as well as the molar absorptivity of dimer band can be obtained based on Eq. (13) from the data treatment of the integrated absorbances of the dimer band. The disparity between two values of dimerization constant determined by two independent sources offers an opportunity to check the consistency of the determination. The standard enthalpy and entropy of dimerization have also been calculated by means of van't Hoff plot, respectively, from the data of temperature-dependent dimerization constants obtained from the monomer bands and dimer bands. (C) 2003 Elsevier B.V. All rights reserved.
New method to analyse IR-studies of monomer-dimer self-association: 2,2-dimethyl-3-ethyl-3-pentanol in carbon disulfide as an example
(2004)
Chen, JS
;
Kao, DY
;
應用化學系
;
Department of Applied Chemistry
Two new equations have been derived to treat the IR data from the monomer-dimer self-association. Equation (9), in the text, is to regress the integrated absorbances of the monomer bands to determine the molar absorptivity of the monomer band, epsilon(m), and the dimerization constant, K. Equation (13), in the text, is to regress those of dimer band to obtain the molar absorptivity of the dimer band, epsilon(d), and dimerization constant K. The self-association in the dilute solution of 2,2-dimethyl-3-ethyl-3-pentanol in carbon disulfide at different temperatures has been used as an example to demonstrate the usage of these two equations. The discrepancy between the values of K at the same temperature determined either from the monomer band or from the dimer band can be used as a criterion for the goodness of determination. The standard enthalpy and entropy of dimerization have also been obtained via a van't Hoff plot from the data of K at different temperatures. The advantages of this new approach have also been discussed.
NMR study of hetero-association accompanying self-association of 2-hydroxyl-4-methyl-pyridine and 2-pyrrolidone in acetonitrile
(2000-12-01)
Luo, WC
;
Lin, CC
;
Lin, JA
;
Kao, DY
;
Chen, JS
This work investigated not only the equilibrium of self-association of 2-pyrrolidone (A) and that of 2-hydroxyl-4-methyl-pyridine (B), but also the hetero-association between A and B in [H-2(3)]acetonitrile through hydrogen bonding using high-resolution nuclear magnetic resonance spectroscopy. Dilution shift data for the protons of the NW group of A and OH group of B were measured over a wide range of temperatures and concentrations. In addition, the monomer shifts, dimer shifts and dimerization constants of self-association and hetero-association were evaluated using a graphic method operating on the dilution chemical shift data. The enthalpy and entropy of dimerization of self-association and hetero-association were also obtained from the van't Hoff plot.