A theoretical study on the oxidation mechanism of triose reductone in reference to L-ascorbic acid

1986 ◽  
Vol 64 (2) ◽  
pp. 360-365 ◽  
Author(s):  
Yasuo Abe ◽  
Hideo Horii ◽  
Setsuo Taniguchi ◽  
Shinichi Yamabe ◽  
Tsutomu Minato
Keyword(s):  
Ascorbic Acid ◽  
Functional Group ◽  
Theoretical Study ◽  
Oxidation Process ◽  
Gradient Methods ◽  
Vibrational Analysis ◽  
Oxidation Mechanism ◽  
Basis Set ◽  
Carbonyl Groups ◽  
Intermediate Species

The oxidation of triose reductone H—CO—C(OH)=C(OH)—H (which has the same functional group as L-ascorbic acid) to dehydroreductone is investigated by abinitio molecular orbital computations. The geometries of the substrate, oxidized product, and of six possible intermediate species are optimized by gradient methods at the STO-3G basis set level. All the species are found to be planar and stable molecules by the vibrational analysis. The most possible oxidation route is shown to consist of four steps. The combination of the enediol and carbonyl groups in the deprotonated molecule 2 gives an effective π conjugation for the electron removal. The oxidation process of L-ascorbic acid is discussed on the basis of the results for triose reductone.

Mechanism of L-ascorbic acid oxidation and dehydro-L-ascorbic acid reduction on a mercury electrode. I. Acid medium

1977 ◽  
Vol 55 (15) ◽  
pp. 2799-2806 ◽  
Author(s):  
Juan José Ruiz ◽  
Antonio Aldaz ◽  
Manuel Dominguez
Keyword(s):  
Electron Transfer ◽  
Ascorbic Acid ◽  
Oxidation Process ◽  
Mercury Electrode ◽  
Oxidation Mechanism ◽  
Limiting Current ◽  
Acid Oxidation ◽  
Rate Determining Step ◽  
Reaction Orders ◽  
Electron Transfers

A polarographic study of the oxidation mechanism of L-ascorbic acid and of the reduction mechanism of dehydro-L-ascorbic acid was carried out in an acid medium.For L-ascorbic acid, the oxidation process involves a two electron transfer and obeys the overall reaction[Formula: see text]The polarographic curve shows that the limiting current is governed by diffusion. On the rising portion of the wave, the two electron oxidation process consists of two consecutive one electron transfers, the second being the rate determining step (rds). The reaction orders, together with the Tafel slopes, were calculated.The reduction of dehydro-L-ascorbic acid at the limiting current is kinetically controlled and involves a two electron transfer. The reaction kinetic pathways were studied and the reaction orders and Tafel slope were calculated. It is deduced that, for low overvoltages, the second one electron transfer is the rate determining step.

scholarly journals Surface Chemical Heterogeneity of Low Rank Coal Characterized by Micro-FTIR and Its Correlation with Hydrophobicity

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 239
Author(s):  
Wei Wang ◽  
Long Liang ◽  
Yaoli Peng ◽  
Maria Holuszko
Keyword(s):  
Surface Chemistry ◽  
Functional Group ◽  
Group Composition ◽  
Contact Angles ◽  
Low Rank ◽  
Surface Chemical ◽  
Carbonyl Groups ◽  
Low Rank Coal ◽  
Different Types ◽  
Aliphatic Carbon

Micro-Fourier transform infrared (micro-FTIR) spectroscopy was used to correlate the surface chemistry of low rank coal with hydrophobicity. Six square areas without mineral impurities on low rank coal surfaces were selected as testing areas. A specially-designed methodology was applied to conduct micro-FTIR measurements and contact angle tests on the same testing area. A series of semi-quantitative functional group ratios derived from micro-FTIR spectra were correlated with contact angles, and the determination coefficients of linear regression were calculated and compared in order to identify the structure of the functional group ratios. Finally, two semi-quantitative ratios composed of aliphatic carbon hydrogen, aromatic carbon hydrogen and two different types of carbonyl groups were proposed as indicators of low rank coal hydrophobicity. This work provided a rapid way to predict low rank coal hydrophobicity through its functional group composition and helped us understand the hydrophobicity heterogeneity of low rank coal from the perspective of its surface chemistry.

Through-Space Transmission of 19F-13C Coupling Via an Intermediate Bond. An Experimental and Theoretical Study

1987 ◽  
Vol 40 (12) ◽  
pp. 1923 ◽  
Author(s):  
ID Rae ◽  
ID Rae ◽  
A Staffa ◽  
A Staffa ◽  
AC Diz ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Lone Pair ◽  
Electron Excitation ◽  
Carbonyl Groups ◽  
Polarization Propagator ◽  
Close Proximity ◽  
Fermi Contact ◽  
Intramolecular Hydrogen ◽  
Intermediate Bond ◽  
Insight Into

In order to obtain a deeper insight into the title effect, several compounds with an F atom very close to a C-H of a nearby functional group were synthesized and the relevant couplings measured. The most conspicuous case was that of 8-fluoro-2-hydroxynaphthalene-1-carbaldehyde where a close proximity between the F and H atoms is the result of fluorine-oxygen repulsion and the formation of an intramolecular hydrogen bond between the hydroxyl and carbonyl groups. The experimental four-bond J(F,CHO) coupling is 26.2 Hz. A compound very similar to this one, but without the OH group, was chosen on which to perform a polarization propagator analysis of the through-space (TS) coupling pathways, at the RPA-INDO level. The expression for the TS coupling in terms of the projected polarization propagator and perturbators was numerically analysed. It is found that this coupling is completely dominated by a TS component of the Fermi contact (FC) term, the main features of which are: ( i ) It decays exponentially with the F-H distance; (ii) Its main contribution comes from an electron excitation involving the F lone-pair, the C-H bond of the CHO moiety and its corresponding antibonding orbital;(iii) The π-type lone-pair does not contribute to the TS coupling pathway of the FC term.

First principle simulation on oxidation mechanism of diethyl ether by nitrogen dioxide

2015 ◽  
Vol 14 (03) ◽  
pp. 1550020 ◽  
Author(s):  
Yuan Yuan ◽  
Wei Hu ◽  
Xuhui Chi ◽  
Cuihua Li ◽  
Dayong Gui ◽  
...  
Keyword(s):  
Diethyl Ether ◽  
Energy Barrier ◽  
Density Functional ◽  
Oxidation Process ◽  
Oxidation Mechanism ◽  
High Energy ◽  
First Principle ◽  
Functional Theory ◽  
The Third ◽  
High Energy Barrier

The oxidation mechanism of diethyl ethers by NO2was carried out using density functional theory (DFT) at the B3LYP/6-31+G (d, p) level. The oxidation process of ether follows four steps. First, the diethyl ether reacts with NO2to produce HNO2and diethyl ether radical with an energy barrier of 20.62 kcal ⋅ mol-1. Then, the diethyl ether radical formed in the first step directly combines with NO2to form CH3CH ( ONO ) OCH2CH3. In the third step, the CH3CH ( ONO ) OCH2CH3was further decomposed into the CH3CH2ONO and CH3CHO with a moderately high energy barrier of 32.87 kcal ⋅ mol-1. Finally, the CH3CH2ONO continues to react with NO2to yield CH3CHO , HNO2and NO with an energy barrier of 28.13 kcal ⋅ mol-1. The calculated oxidation mechanism agrees well with Nishiguchi and Okamoto's experiment and proposal.

Liquid Crystalline Properties of 4,4and#39;-methylenebis(N-(4-Alkanoxybenzylidene)aniline): Synthesis, Characterization, and Theoretical study

2019 ◽  
Vol 41 (6) ◽  
pp. 1107-1107
Author(s):  
Mohammed Taha Yaseen and Abdullah Hussein Kshash Mohammed Taha Yaseen and Abdullah Hussein Kshash
Keyword(s):  
Liquid Crystalline ◽  
Theoretical Study ◽  
Basis Set ◽  
Spectroscopic Techniques ◽  
Benzene Nucleus ◽  
Crystal Properties ◽  
Ft Ir ◽  
Alkoxy Groups ◽  
Gaussian Program ◽  
Mesomorphic Properties

The paper presents six homologues series of Schiff bases ether compounds distinguished by the length of terminal alkoxy groups which substituted on a side benzene nucleus. The above structures were demonstrated through the use of spectroscopic techniques, like FT- IR and 1H-NMR. Polarized hot stage optical microscopy was used to study both mesomorphic properties and phase transitions. The results showed that out of the six compounds only three (B2, B3 and B4) were pure (marble) nematic mesophase, while no liquid crystal properties for (B5, B6 and B7) compounds. The theoretical study for the electronic structures was intended to study the effects of alkyl chain length on the electronic structure by using Gaussian program, DFT and 6-31G as basis set. The theoretical results indicate that there is no effect to the terminal substituted alkoxy groups on the HOMO energies but there is an effect on LUMO energies through decreasing energy for the prepared compounds.

Temperature-Driven Oxidation Behavior of Pure Iron Surface Investigated by Time-Resolved EXAFS Measurements

1998 ◽  
Vol 524 ◽  
Author(s):  
S. J. Doh ◽  
J. M. Lee ◽  
D. Y. Noh ◽  
J. H. Je
Keyword(s):  
Heat Treatment ◽  
Oxidation Behavior ◽  
Oxidation Process ◽  
Rapid Heating ◽  
Oxidation Mechanism ◽  
Front Surface ◽  
Time Resolved ◽  
Treatment Conditions ◽  
Surface Front ◽  
Prolonged Heat

ABSTRACTThe surface-front oxidation mechanism of iron was investigated by time-resolved, glancingangle Fe K-edge fluorescence EXAFS measurements at various oxidation temperatures of 200-700 C. The glancing angle was chosen according to the depth of the oxide layer, roughly 1500-2000A. The oxidation behavior under rapid heating(up to 600°C within 10 minutes) was compared with the slowly heated oxidation process using the Quick-EXAFS measurements. In the slowly heated process, Fe3O4 was the dominating phase at a relatively low temperature (300-400 C) initially. However, at a relatively high temperature (above 600°C), the Fe2O3 and FeO crystalline phases are gradually enriched as the successive oxidation process involving intrusive oxygen proceeded. Remarkably under a prolonged heat treatment above 600°C, the stable FeO phase that exists in a deep-lying interface structure and Fe2O3 phase eventually dominates the thick front-surface structure. In a quickly heated process, however, Fe3O4 phase is less dominating, which is contradictory to the commonly accepted oxidation models. The EXAFS results are discussed in conjunction with the x-ray diffraction features under the same heat treatment conditions.

scholarly journals Experimental and Theoretical Study of the Enthalpy of Formation of 3,6-Diphenyl-1,2,4,5-Tetroxane Molecule

2002 ◽  
Vol 2 ◽  
pp. 455-460 ◽  
Author(s):  
N.L. Jorge ◽  
L.C.A. Leiva ◽  
M.G. Castellanos ◽  
M.E. Gomez Vara ◽  
L.F.R. Cafferata ◽  
...  
Keyword(s):  
Vapor Pressure ◽  
Enthalpy Of Formation ◽  
Vapor Phase ◽  
Theoretical Study ◽  
Theoretical Calculations ◽  
Basis Set ◽  
Sublimation Enthalpy ◽  
Combustion Heat ◽  
Different Temperatures ◽  
The Enthalpy Of Formation

We report the results obtained for the experimental determination and the theoretical calculation of the enthalpy of formation of 3,6-diphenyl-1,2,4,5-tetroxane molecule. The experimental work was performed using a macrocalorimeter to measure the combustion heat, and the sublimation enthalpy was determined via the measurement of the vapor pressure at equilibrium with the vapor phase at different temperatures resorting to the Clapeyron-Claussius equation. Theoretical calculations were performed using semiempirical AM1 and PM3 methods as well asab initiotechniques at the 3-21, 6-31G(d,p), and 6-311G(d,p) basis set levels.

scholarly journals Theoretical Study of Solvent Effects on the Electronic and Thermodynamic Properties of Tetrathiafulvalene (TTF) Molecule Based on DFT

2021 ◽  
pp. 42-54
Author(s):  
Rabiu Nuhu Muhammad ◽  
N. M. Mahraz ◽  
A. S Gidado ◽  
A. Musa
Keyword(s):  
Thermodynamic Properties ◽  
Bond Length ◽  
Density Functional ◽  
Theoretical Study ◽  
Energy Gap ◽  
Basis Set ◽  
Basis Sets ◽  
Frontier Molecular Orbital ◽  
Orbital Energy ◽  
Chemical Hardness

Tetrathiafulvalene () is an organosulfur compound used in the production of molecular devices such as switches, sensors, nonlinear optical devices and rectifiers. In this work, a theoretical study on the effects of solvent on TTF molecule was investigated and reported based on Density Functional Theory (DFT) as implemented in Gaussian 03 package using B3LYP/6-31++G(d,p) basis set. Different solvents were introduced as a bridge to investigate their effects on the electronic structure. The HUMO, LUMO, energy gap, global chemical index, thermodynamic properties, NLO and DOS analysis of the TTF molecule in order to determine the reactivity and stability of the molecule were obtained. The results obtained showed that the solvents have effects on the electronic and non-linear-optical properties of the molecule. The optimized bond length revealed that the molecule has strong bond in gas phase with smallest bond length of about 1.0834Å than in the rest of the solvents. It was observed that the molecule is more stable in acetonitrile with HOMO-LUMO gap and chemical hardness of 3.6373eV and 1.8187eV respectively. This indicates that the energy gap and chemical hardness of TTF molecule increases with the increase in polarity and dielectric constant of the solvents. The computed results agreed with the results in the literature. The thermodynamics and NLO properties calculation also indicated that TTF molecule has highest value of specific heat capacity (Cv), total dipole moment () and first order hyperpolarizability () in acetonitrile, while acetone has the highest value of entropy and toluene has a slightly higher value of zero point vibrational energy (ZPVE) than the rest of the solvents. The results show that careful selection of the solvents and basis sets can tune the frontier molecular orbital energy gap of the molecule and can be used for molecular device applications.

Green Oxidation Process in the Synthesis of LLM-105 with H2O2/Peroxotungstate System and its Theoretical Study

2016 ◽  
Vol 53 (5) ◽  
pp. 1386-1394 ◽  
Author(s):  
Jie Zhu ◽  
Xue-Jing Zhao ◽  
Peng-Cheng Wang ◽  
Ming Lu
Keyword(s):  
Theoretical Study ◽  
Oxidation Process ◽  
Green Oxidation
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