Diffusion in paraffin hydrocarbons. Diffusion of cyclohexylbromide in n-alkanes at 25°C

Amu, Thomas C.

doi:10.1039/f19797501226

Cited by 23 publications

(4 citation statements)

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“…Amu reported the diffusion coefficient of cyclohexylbromide in various paraffin hydrocarbons. He found that in these solvents x is not a constant but decreases with increasing chain length of the hydrocarbons; that is, x corresponding to n -heptadecane (C 17 ) is about 1.8 times smaller than that corresponding to n -hexane (C 6 ).…”

Section: Resultsmentioning

confidence: 99%

Transient Effect in Fluorescence Quenching by Electron Transfer. 4. Long-Range Electron Transfer in a Nonpolar Solvent

et al. 1999

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The transient effect in fluorescence quenching observed in a viscous nonpolar solvent, liquid paraffin, was measured and analyzed in order to study the mechanism of electron transfer fluorescence quenching in such solvents. The method of analysis is similar to that adopted in previous papers (J. Phys. Chem. 1995, 99, 5354; 1996, 100, 4064) to study electron transfer in polar solvents. The difference from the previous method is that a function of the form A exp[− b(r − r 0)] was used as the electron transfer rate constant k(r) instead of the Marcus equation and that the dependence of the steady-state fluorescence intensity on the quencher concentration was also analyzed in addition to the fluorescence decay at high quencher concentrations (≥50 mM). The parameters A and b and the diffusion coefficient D were determined from these analyses. The distribution of quenching distance was calculated using these parameter values. The distribution shows that the quenching occurs at distances longer than the contact distances of the fluorescer and quencher molecules. It was concluded that, even in nonpolar liquid paraffin, quenching occurs by long-range electron transfer rather than by exciplex formation as long as the ΔG of electron transfer is negative and far from 0 eV. The relation between electron transfer and exciplex formation in nonpolar solvents was discussed.

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Section: Resultsmentioning

confidence: 99%

Transient Effect in Fluorescence Quenching by Electron Transfer. 4. Long-Range Electron Transfer in a Nonpolar Solvent

et al. 1999

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“…We refer to the studies of Amu for a more detailed discussion. 19 A common feature of the data is the characteristic negative values of the hydrodynamic virial coefficient, k D . The latter is defined by where A 2 is the second virial coefficient, M the molar mass, k f the concentration-dependent friction factor, and V 2 the solute partial specific volume.…”

Section: Resultsmentioning

confidence: 99%

“…We note here that for particles larger than the solvent molecules, the factor 6π in eq 7 is appropriate, whereas for diffusing particles only slightly larger than or approximately equal to the size of the solvent molecules, the factor should be replaced by 4π. We refer to the studies of Amu for a more detailed discussion . A common feature of the data is the characteristic negative values of the hydrodynamic virial coefficient, k D .…”

Section: Resultsmentioning

confidence: 99%

Inclusion Complexes between Cyclodextrins and Triblock Copolymers in Aqueous Solution: A Dynamic and Static Light-Scattering Study

1997

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Simultaneous static and dynamic light experiments have been made on various cyclodextrins and cyclodextrin derivatives, as well as the inclusion complexes formed between different polyethylene oxide/polypropylene oxide triblock copolymers (PEO-PPO-PEO) (pluronics) and dimethyl--cyclodextrin (DIMEB). The inclusion complexes formed between DIMEB and pluronics are highly soluble, in contrast to the insoluble complexes formed between -cyclodextrin and the same substances. The static light-scattering (LS) data show that approximately 11 DIMEB molecules thread onto the copolymer chains and are located on the PPO block. With the inverse structure (PPO-PEO-PPO), about seven DIMEB molecules are present in the complex. NMR measurements are used to substantiate complex formation by means of characteristic changes in the proton signals. Hydrodynamic radii obtained from the dynamic LS data at infinite dilution for the cyclodextrins correspond well with dimensions determined using X-ray methods. Inverse Laplace transformation (ILT) allowed resolution of the relaxational modes from the cyclodextrin/pluronic complex and the excess cyclodextrin. The complexes formed with the DIMEB are shown to be significantly larger than the copolymer unimers, which may be due to accentuation of steric hindrance to flexing in the PPO block. With the inverse pluronic structure, on the other hand, the complex is smaller in radius than the unimer. At temperatures above which the copolymer forms micelles, addition of DIMEB inhibits both cluster formation and micellization of the pluronics and also prevents network formation with the inverse pluronic, whereas the trimethyl analogue (TRIMEB) does not have this effect.

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“…where B is the Boltzmann constant (1.3806 ϫ 10 Ϫ23 J K Ϫ1 ), c is a constant ͑4 and 6 for the slip and stick boundary conditions, respectively͒, 38,39 is the solvent viscosity, and r s is the radius of the diffusing molecule modeled as a sphere. The obtained dependence of D O 2 on does not fit that expected from the Stokes-Einstein equation, as readily seen from Fig.…”

Section: Discussionmentioning

confidence: 99%

Electroreduction of Dioxygen in 1-n-Alkyl-3-methylimidazolium Tetrafluoroborate Room-Temperature Ionic Liquids

Zhang

Okajima

Matsumoto

et al. 2004

J. Electrochem. Soc.

117

131

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The electrode reaction of the molecular oxygen (O 2 )/superoxide ion (O 2 Ϫ) redox couple at glassy carbon ͑GC͒, gold ͑Au͒, and platinum ͑Pt͒ electrodes in three 1-n-alkyl-3-methylimidazolium tetrafluoroborate (AMIBF 4 ) room-temperature ionic liquids ͑RTILs͒, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-n-propyl-3-methylimidazolium tetrafluoroborate, and 1-n-butyl-3methylimidazolium tetrafluoroborate, has been analyzed quantitatively using cyclic voltammetry, normal pulse voltammetry, and hydrodynamic chronocoulometry ͑HCC͒. Cyclic voltammetric measurements showed that the redox reaction of the O 2 /O 2 Ϫ couple in these RTILs is a quasi-reversible process and that the resulting O 2 Ϫ is stable. The relevant thermodynamic and kinetic parameters ͓the formal potential (E 0 Ј), the standard rate constant (k 0 ), and the cathodic transfer coefficient (␣ c )] of the O 2 /O 2 Ϫ redox couple were evaluated using cyclic and normal pulse voltammetry: ͑i͒ the E 0 Ј values are almost the same irrespective of the media and electrode materials examined, i.e., ca. Ϫ1.0 V vs. an internal standard potential of the ferrocene ͑Fc͒/ferricinium ion (Fc ϩ ) redox couple, ͑ii͒ the k 0 value is dependent on the electrode material and increases in the order k 0 (Pt) Ͻ k 0 (Au) Ͻ k 0 (GC), and ͑iii͒ the values of ␣ c are in the range of 0.35-0.47. The diffusion coefficients (D O 2 ) and saturated concentrations (C O 2 ) of O 2 in three AMIBF 4 RTILs were also determined by HCC.

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Diffusion in paraffin hydrocarbons. Diffusion of cyclohexylbromide in n-alkanes at 25°C

Cited by 23 publications

References 0 publications

Transient Effect in Fluorescence Quenching by Electron Transfer. 4. Long-Range Electron Transfer in a Nonpolar Solvent

Transient Effect in Fluorescence Quenching by Electron Transfer. 4. Long-Range Electron Transfer in a Nonpolar Solvent

Inclusion Complexes between Cyclodextrins and Triblock Copolymers in Aqueous Solution: A Dynamic and Static Light-Scattering Study

Electroreduction of Dioxygen in 1-n-Alkyl-3-methylimidazolium Tetrafluoroborate Room-Temperature Ionic Liquids

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