Study of local structures formed in ethanol solutions. Determination of equilibrium constants by light scattering and infrared spectra

The composition, optical characteristics, molar absorption coefficients and equilibrium constants of the reactions of formation of the ML and ML2 complexes of both reagents with cadmium(II) ions were determined by graphical analysis and numerical interpretation of the absorbance-pH curves by the modified SQUAD-G program. Optimal conditions were proposed for the spectrophotometric determination of Cd in 10% v/v ethanol medium in the presence of 0.1% w/v Triton X-100 or 1% w/v Brij 35. BrPADAP and ClPADAP are the most sensitive spectrophotometric reagents for the determination of cadmium(II) ions (ε = 1.28-1.44 . 105 mmol-1 cm2 at 560 nm and pH 8.0-9.5) with a high colour contrast in the reaction (Δλmax ~117 nm) and a selectivity similar to that of other N-heterocyclic azodyes (PAR, PAN, etc.).

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Preparation of graft copolymers by the reaction of polymeric acyl chlorides with monohydroxy-terminated polymers: An introductory study

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19881735 ◽

1988 ◽

Vol 53 (8) ◽

pp. 1735-1744 ◽

Cited By ~ 1

Author(s):

Jitka Horská ◽

Jaroslav Stejskal ◽

Pavel Kratochvíl ◽

Aubrey D. Jenkins ◽

Eugenia Tsartolia ◽

...

Keyword(s):

Light Scattering ◽

Chemical Composition ◽

Statistical Model ◽

Graft Copolymers ◽

Coupling Reaction ◽

Molecular Characteristics ◽

Gel Formation ◽

Acyl Chlorides ◽

Molecular Weights

An attempt was made to prepare well-defined graft copolymers by the coupling reaction between acyl chloride groups located along the backbone chain and monohydroxy-terminated grafts prepared separately. The molecular weights and the parameters of heterogeneity in chemical composition of the products were determined by light scattering and osmometry. The determination of molecular characteristics revealed that the degree of grafting was low. The results therefore could not be confronted with a statistical model at this stage. The problems encountered in the synthesis, e.g., gel formation, and the data relating to the soluble products are discussed.

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Spectrophotometric study of the acid-base and optical properties of the 5-bromo and 5-chloro derivatives of 2-(2-pyridylazo)-5-(diethylamino)phenol (BrPADAP, ClPADAP) and their complexation equilibria with zinc(II) ions

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19822676 ◽

1982 ◽

Vol 47 (10) ◽

pp. 2676-2691 ◽

Cited By ~ 6

Author(s):

Miroslav Macka ◽

Vlastimil Kubáň

Keyword(s):

Equilibrium Constants ◽

Spectrophotometric Study ◽

Graphical Analysis ◽

Alkaline Media ◽

Acid Base ◽

Ethanol Medium ◽

Triton X ◽

Mixed Water ◽

Derivatives Of

The optical and acid-base characteristics of BrPADAP and ClPADAP were studied in mixed water-ethanol and water-DMF media and in 10% ethanol medium in the presence of cationic, anionic and nonionic tensides. The composition, optical characteristics, molar absorption coefficients and equilibrium constants of the ML and ML2 complexes with zinc(II) ions were found by graphical analysis and numerical interpretation of the absorbance curves by the modified SQUAD-G program. Optimal conditions were found for the spectrophotometric determination of Zn(II) in the presence of 0.1% Triton X-100 or 1% Brij 35 in alkaline media with pH = 6.5-10. BrPADAP and ClPADAP are the most sensitive reagents (ε = 1.3-1.6 . 105 mmol-1 cm2 at 557 and 560 nm, respectively) for the determination of zinc with high colour contrast of the reaction (Δλ = 104 nm) and selectivity similar to that for the other N-heterocyclic azodyes (PAN, PAR, etc.).

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Recognition of hydrogen isotopomers by an open-cage fullerene

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2011.0629 ◽

2013 ◽

Vol 371 (1998) ◽

pp. 20110629 ◽

Cited By ~ 4

Author(s):

Yasujiro Murata ◽

Shih-Ching Chuang ◽

Fumiyuki Tanabe ◽

Michihisa Murata ◽

Koichi Komatsu

Keyword(s):

Equilibrium Constants ◽

Equilibrium Mixture ◽

Size Difference ◽

Binding Affinities ◽

Kinetic Isotope ◽

Molecular Sizes ◽

Lower Temperature ◽

Kinetics Of ◽

Pressure Hydrogen

We present our study on the recognition of hydrogen isotopes by an open-cage fullerene through determination of binding affinity of isotopes H 2 /HD/D 2 with the open-cage fullerene and comparison of their relative molecular sizes through kinetic-isotope-release experiments. We took advantage of isotope H 2 /D 2 exchange that generated an equilibrium mixture of H 2 /HD/D 2 in a stainless steel autoclave to conduct high-pressure hydrogen insertion into an open-cage fullerene. The equilibrium constants of three isotopes with the open-cage fullerene were determined at various pressures and temperatures. Our results show a higher equilibrium constant for HD into open-cage fullerene than the other two isotopomers, which is consistent with its dipolar nature. D 2 molecule generally binds stronger than H 2 because of its heavier mass; however, the affinity for H 2 becomes larger than D 2 at lower temperature, when size effect becomes dominant. We further investigated the kinetics of H 2 /HD/D 2 release from open-cage fullerene, proving their relative escaping rates. D 2 was found to be the smallest and H 2 the largest molecule. This notion has not only supported the observed inversion of relative binding affinities between H 2 and D 2 , but also demonstrated that comparison of size difference of single molecules through non-convalent kinetic-isotope effect was applicable.

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