| Summary: | 碩士 === 國立交通大學 === 應用化學研究所 === 86 ===
A graphic method for the simultaneous determination of teh monomer shift, dimer shift and dimerization constant of the ionpairing system from the dilution NMR shift data is proposed in conjunction with Bromley's equation.
logr±= -Am|Z+Z-|√Im/1+ai√Im+(0.06+0.6Bm|Z+Z-|Im)/[1+(1.5Im|Z+Z-|)]2+BmIm where Am=e3/2.3026*(εkT)3/2*(2πρ0L./1000)1/2, Bm=(8πLe2ρ0/1000εkT)1/2 r± is activity coefficient, Im ion strength, ρ0 density of solvent, ε dielectric constant of the solvent, k Boltzmann constant, L Avogadro's number, e the absolute value of electronic charge, Z valence, ai=1 in case of 1:1 aqueous electrolyte solutions.
We deal with six systems: Methyl triphenyl-phosphonium bromide in D20 and CD3SOCD3, Benzyl triphenyl-phosphonium bromide, Benzyl triphenyl-phosphonium chloride in CD3SOCD3, (Bromomethyl) triphenyl-phosphonium bromide in CD3SOCD3 and DMF. If the value of dielectric constant is small, the improvement from the no-modified to the modified dimerization constants is appreciable. As the concetrations were diluted, the more precise value of teh monomer shifts, dimer shifts and dimerization constants are obtained. Standard enthalpies and entropies of self-association were also obtained by van't Hoff plots.
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