Structural changes of flavylium salts. I. Polarographic and spectrometric examination of 7,4'-Dihydroxyflavylium perchlorate

1967 ◽  
Vol 20 (4) ◽  
pp. 731 ◽  
Author(s):  
KA Harper ◽  
BV Chandler
Keyword(s):  
Diffusion Coefficients ◽  
Ring Opening ◽  
Structural Changes ◽  
Molecular Changes ◽  
Electrode Reactions ◽  
And Diffusion

From polarographic and spectrometric studies a sequence of molecular changes is proposed for 7,4?-dihydroxyflavylium perchlorate in solutions of increasing pH in the absence of oxygen. Below pH 2 the flavylium ion is stable. Between pH 2 and 7.5 the chalcone is formed, the reaction occurring rapidly and completely in less than 1 hr between pH 4 and 6. This transformation involves the anhydrobase, the ionized form of which is stable from pH 7.5 to 10. Further increase in pH causes ring opening to the ionized chalcone, which is almost instantaneously formed at pH 13. Electrode reactions are proposed and diffusion coefficients calculated for the various forms.

Structural changes of flavylium salts. III. Polarographic and spectrometric examination of 3,7,4'-trihydroxyflavylium perchlorate

1967 ◽  
Vol 20 (12) ◽  
pp. 2691 ◽  
Author(s):  
KA Harper
Keyword(s):  
Ring Opening ◽  
Structural Changes ◽  
Equilibrium Mixture ◽  
Open Chain ◽  
Enolic Form ◽  
Molecular Changes ◽  
The Stability ◽  
Dihydroxy Compound

The molecular changes undergone by 3,7,4?-trihydroxyflavylium perchlorate in aqueous methanolic solutions with increasing pH were followed by polarography and spectrometry, and the effect of the hydroxyl at C3 observed by comparison with the behaviour of 7,4?- dihydroxyflavylium perchlorate. The trihydroxyflavylium ion is less stable above pH 2 than the dihydroxy compound and forms the open-chain α-diketone, probably via the 3-keto pseudobase. The stability of the enolic form of the pseudobase increases at higher pH and is favoured from pH 5 to pH 9. At pH 6.5 the anhydrobase appears in the equilibrium mixture and at pH 9 becomes stabilized by ionization. Although the α- hydroxychalcone was not detectable at lower pH, at pH 10 ring opening gives the ionized a-hydroxychalcone, rather than the ionized diketone, and equilibrium shifts in this direction as the pH is raised further.

PREDICTION OF THE TRANSPORT PROPERTIES OF SF6 WITH O2, CO2, CF4, N2 AND CH4 MIXTURES AT LOW DENSITY BY THE INVERSION METHOD (PART II)

2004 ◽  
Vol 03 (01) ◽  
pp. 69-90 ◽  
Author(s):  
BEHZAD HAGHIGHI ◽  
ALIREZA HASSANI DJAVANMARDI ◽  
MOHAMAD MEHDI PAPARI ◽  
MOHSEN NAJAFI
Keyword(s):  
Potential Energy ◽  
Diffusion Coefficients ◽  
Potential Energy Function ◽  
Model Potential ◽  
Inversion Method ◽  
Low Density ◽  
Initial Model ◽  
Lennard Jones ◽  
Inversion Procedure ◽  
And Diffusion

Viscosity and diffusion coefficients for five equimolar binary gas mixtures of SF 6 with O 2, CO 2, CF 4, N 2 and CH 4 gases are determined from the extended principle of corresponding states of viscosity by the inversion technique. The Lennard–Jones 12-6 (LJ 12-6) potential energy function is used as the initial model potential required by the technique. The obtained interaction potential energies from the inversion procedure reproduce viscosity within 1% and diffusion coefficients within 5%.

scholarly journals Boundary behavior and product-form stationary distributions of jump diffusions in the orthant with state-dependent reflections

2008 ◽  
Vol 40 (02) ◽  
pp. 529-547
Author(s):  
Francisco J. Piera ◽  
Ravi R. Mazumdar ◽  
Fabrice M. Guillemin
Keyword(s):  
Random Fields ◽  
Diffusion Coefficients ◽  
Boundary Behavior ◽  
Stationary Regime ◽  
Product Form ◽  
Local Times ◽  
Nonnegative Orthant ◽  
State Dependent ◽  
The Times ◽  
And Diffusion

In this paper we consider reflected diffusions with positive and negative jumps, constrained to lie in the nonnegative orthant of ℝ n . We allow for the drift and diffusion coefficients, as well as for the directions of reflection, to be random fields over time and space. We provide a boundary behavior characterization, generalizing known results in the nonrandom coefficients and constant directions of the reflection case. In particular, the regulator processes are related to semimartingale local times at the boundaries, and they are shown not to charge the times the process expends at the intersection of boundary faces. Using the boundary results, we extend the conditions for product-form distributions in the stationary regime to the case when the drift and diffusion coefficients, as well as the directions of reflection, are random fields over space.

scholarly journals The rate of evaporation of droplets. Evaporation and diffusion coefficients, and vapour pressures of dibutyl phthalate and butyl stearate

1946 ◽  
Vol 186 (1006) ◽  
pp. 368-390 ◽  
Keyword(s):  
Diffusion Coefficients ◽  
Atmospheric Pressure ◽  
Dibutyl Phthalate ◽  
Droplet Evaporation ◽  
Medium Size ◽  
Good Accordance ◽  
Butyl Stearate ◽  
Rate Of Evaporation ◽  
Low Pressures ◽  
And Diffusion

The rate of evaporation of drops of dibutyl phthalate and butyl stearate of radius approx. 0.5 mm. has been studied by means of a microbalance over a range of atmospheric pressures down to approx. 0*1 mm. of mercury. Wide departures from Langmuir’s evaporation formula were found to occur at these low pressures, but results are in good accordance with the theory of droplet evaporation advanced by Fuchs which hitherto has not been tested experimentally. This experimental verification of Fuch’s theory for droplets of medium size evaporating at low pressures shows that the theory can be applied to the evaporation of very small drops at atmospheric pressure. The vapour pressures of the above liquids have been measured by Knudsen’s method and the evaporation and diffusion coefficients calculated fro n the experimental data.

Aluminophosphate Glasses with High Sulfate Content

1994 ◽  
Vol 353 ◽  
Author(s):  
Sergey V. Stefanovsky ◽  
Igor A. Ivanov ◽  
Anatolii N. Gulin
Keyword(s):  
Diffusion Coefficients ◽  
Glass Structure ◽  
Chemical Durability ◽  
Electric Resistivity ◽  
Melting Points ◽  
Sulfate Content ◽  
Leach Rate ◽  
High Sulfate ◽  
Aluminophosphate Glasses ◽  
And Diffusion

AbstractTo immobilize a high sulfate radioactive wastes a system Na2O-A12O3-P2O5-SO3 has been chosen as one where glasses have a relatively low melting points and good chemical durability. Glasses within partial system 44 Na2O, 20 A12O3 (36-x) P2O5 x SO3 have been prepared at 1000 °C. A possibility of assimilation up to 12 mole % of SO3 has been established. The basic properties of sulfate-containing glasses as density, microhardness, thermal expansion coefficient, transformation and deformation temperatures, viscosity, electric resistivity, leach rate of ions and diffusion coefficients of 22Na, 35S, 90Sr and 137Cs have been measured. Glass structure by infrared and EPR spectroscopies has been investigated.

Calculation of viscosity and diffusion coefficients in binary mixtures of dilute gases

2017 ◽  
Vol 11 ◽  
pp. 283-296
Author(s):  
A. F. Bogatyrev ◽  
O. A. Makeenkova ◽  
V. R. Belalov ◽  
M. A. Kucherenko
Keyword(s):  
Binary Mixtures ◽  
Diffusion Coefficients ◽  
Dilute Gases ◽  
And Diffusion
Sign in / Sign up

Export Citation Format

Share Document