Browsing by Author "Lay, JL"

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NMR study of hydrogen bonding association of 2-isopropylphenol in carbon tetrachloride, acetone, dimethyl sulphoxide and acetonitrile
(2001)
Luo, WC
;
Lay, JL
;
Chen, JS
;
應用化學系
;
Department of Applied Chemistry
This study investigates the association of 2-isopropylphenol through hydrogen bonding in carbon tetrachloride, [H-2(6)]acetone, [H-2(3)]acetonitrile and [H-2(6)]dimethyl sulphoxide by using high resolution nuclear magnetic resonance spectroscopy. Chemical shifts of the hydroxyl proton were measured over a wide range of temperature and concentration. The chemical shift data were treated by a graphical method to determine the monomer shift, dimer shift and dimerization constant. The enthalpy and entropy of dimerization were determined via a van't Hoff plot from the temperature variation of the dimerization constant.
NMR study of hydrogen bonding association of some sterically hindered alcohols in carbon tetrachloride, chloroform and cyclohexane
(2002)
Luo, WC
;
Lay, JL
;
Chen, JS
;
應用化學系
;
Department of Applied Chemistry
The self-association (dimerization) due to hydrogen bonding for some alcohols with bulky side chains was investigated by nuclear magnetic resonance spectroscopy. The systems studied include 2,4-dimethyl-3-pentanol or 3-methyl-3-pentanol in [H-2(12)]cyclohexane, carbon tetrachloride or [H-2(1)]chloroform, and 2,3,4-trimethyl-3-pentanol in carbon tetrachloride. The dilution shift data of hydroxyl proton were measured and employed to deduce the monomer shift, dimer shift and dimerization constant with the help of a graphic method. Use of van't Hoff plot for dimerization constants thus obtained at different temperature gave the enthalpy and entropy of dimerization. Also discussed herein is the effect of substituent hindrance and dielectric constant of solvent on the self-association.