Structure - Activity Relations for the Photodegradation Reactions of Monosubstituted Anilines in TiO2 Suspensions

2002 ◽  
Vol 5 (1) ◽  
Author(s):  
Nevim San ◽  
Zekiye Çımar
Keyword(s):  
Rate Constants ◽  
Molecular Orbital Calculations ◽  
Hartree Fock ◽  
Degradation Reactions ◽  
Structure Activity ◽  
Degradation Rates ◽  
Structure Activity Relations ◽  
Self Consistent Field ◽  
Semi Empirical ◽  
Kinetics Of

AbstractThe kinetics of the photocatalytic degradation reactions of nine different monosubstituted anilines have been investigated experimentally and theoretically. With the intention of finding certain indices in order to determine the degradation rates of aromatic pollutants, geometry optimizations of the anilines have been performed with the semi-empirical PM3 method. The molecular orbital calculations have been carried out by a self-consistent field SCF method using the restricted Hartree-Fock RHF formalism. The correlations between the apparent first-order rate constants and the molecular properties of the compounds have been examined. Three different quantitative structure-activity relationships, QSARs were developed expressing the logarithms of the rate constants in terms of the Brown constants σ

Carbohydrates in alkaline systems. II. Kinetics of the transformation and degradation reactions of cellobiose, cellobiulose, and 4-O-β-D-glucopyranosyl-D-mannose in 1 M sodium hydroxide at 22 °C

1969 ◽  
Vol 47 (21) ◽  
pp. 3957-3964 ◽  
Author(s):  
Donald J. MacLaurin ◽  
John W. Green
Keyword(s):  
Sulfuric Acid ◽  
Sodium Hydroxide ◽  
Column Chromatography ◽  
Rate Constants ◽  
Reaction Rate ◽  
Reaction System ◽  
Reaction Rate Constants ◽  
Degradation Reactions ◽  
Fructose 2 ◽  
Kinetics Of

Rates of isomerization, epimerization, and degradation reactions were measured for cellobiose (7), cellobiulose (8), and 4-O-β-D-glucopyranosyl-D-mannose (9) at 0.001 M in 1 M NaOH under N2 in the dark at 22 °C. Reaction system resolution was by column chromatography on anion resins in the borate form. Assay for D-glucose (1), D-fructose (2), D-mannose (3), and 7,8, and 9 was by continuous automated colorimetry of column effluent with orcinol–sulfuric acid as reagent. Reaction rate constants (h−1) found: k78 0.078, k79 0.0005, k7,10 0.002, k87 0.022, k89 0.003 k81 0.065, k8,12 0.023, k97 0.002, k98 0.013, k9,11 0.006 where 10,11, and 12 are other products than 1,2,3,7,8, and 9. Details for preparation of 8 and 9 are given.

Stability of NADPH: effect of various factors on the kinetics of degradation.

1986 ◽  
Vol 32 (2) ◽  
pp. 314-319 ◽  
Author(s):  
J T Wu ◽  
L H Wu ◽  
J A Knight
Keyword(s):  
Ionic Strength ◽  
Rate Constants ◽  
Degradation Rate ◽  
Neutral Ph ◽  
Degradation Reactions ◽  
Hydronium Ion ◽  
Effects Of Ph ◽  
Reaction Orders ◽  
Kinetics Of Degradation ◽  
Kinetics Of

Abstract Seeking to minimize degradation of NADPH during storage, reagent preparation, and assays, we investigated the effects of pH, temperature, and ionic strength as well as the effects of phosphate and acetate. NADH was also included for comparison. Our results indicate that the rate of degradation of NADPH is proportional most importantly to temperature and concentrations of hydronium ion, but also to concentrations of phosphate and acetate. The degradation rate decreased with increasing ionic strength at neutral pH, but increased slightly at lower pH. NADPH generally is less stable than NADH under the same conditions. The reaction orders with respect to hydronium ion and anions were near 1 for NADH degradation reactions, about 0.5 for NADPH. Rate constants for NADH and NADPH differed more at higher pH and lower phosphate and acetate concentrations.

Modeling of the Photocatalytic Degradation Reactions of Aromatic Pollutants: A Solvent Effect Model

2007 ◽  
Vol 10 (1) ◽  
Author(s):  
Murat Kılıç ◽  
Nevim San ◽  
Zekiye Çınar
Keyword(s):  
Transition State ◽  
Photocatalytic Degradation ◽  
Branching Ratio ◽  
Product Distribution ◽  
State Theory ◽  
Molecular Orbital Calculations ◽  
Reaction Paths ◽  
Degradation Reactions ◽  
Effect Model ◽  
Semi Empirical

AbstractThe photocatalytic degradation reaction of 1,3-dihydroxybenzene has been modeled theoretically. With the intention of predicting the primary intermediates and the product distribution, geometry optimizations of the reactants, the product radicals and transition state complexes have been performed with the semi-empirical PM3 method. The molecular orbital calculations have been carried out by an SCF method using RHF or UHF formalisms. Solvation effects have been computed by DFT calculations at the B3LYP/6-31G* level using COSMO as the solvation model. Based on the results of the quantum mechanical calculations, the rate constants of the four possible reaction paths have been calculated by means of Transition state Theory. Three predictors have been determined for the prediction of the most probable transition state and the reaction path. A branching ratio for each of the reaction paths has been calculated and the most probable intermediate has been determined. Finally, the results obtained have been compared to the experimental results in order to assess the reliability of the proposed model.

Carbohydrates in alkaline systems. I. Kinetics of the transformation and degradation of D-glucose, D-fructose, and D-mannose in 1 M sodium hydroxide at 22 °C

1969 ◽  
Vol 47 (21) ◽  
pp. 3947-3955 ◽  
Author(s):  
Donald J. MacLaurin ◽  
John W. Green
Keyword(s):  
Sulfuric Acid ◽  
Sodium Hydroxide ◽  
Column Chromatography ◽  
Rate Constants ◽  
Reaction Rate ◽  
Reaction System ◽  
Reaction Rate Constants ◽  
Degradation Reactions ◽  
Fructose 2 ◽  
Kinetics Of

Rates of isomerization, epimerization, and degradation reactions were measured for D-glucose (1), D-fructose (2), and D-mannose (3) at 0.002 M in 1 M NaOH under N2 in the dark at 22 °C. Reaction system resolution was by column chromatography on anion resins in the borate form. Assay for 1, 2, and 3 was by continuous automated colorimetry of column effluent using orcinol/sulfuric acid as a reagent. D-Allose and D-altrose were not detected. Reaction rate constants (h−1) found: k12 0.038, k13 0.0005, k15 0.002, k21 0.036, k23 0.006, k24 0.072, k31 0.0005, k32 0.011, k36 0.002, where 4, 5, and 6 are products formed from 1, 2, or 3, respectively.

Influence of fluoro-substitution on the planarity of 4-chlorobiphenyl (PCB 3)

2007 ◽  
Vol 63 (2) ◽  
pp. 319-327 ◽  
Author(s):  
G. Luthe ◽  
D. C. Swenson ◽  
L. W. Robertson
Keyword(s):  
Computer Calculation ◽  
Molecular Orbital Calculations ◽  
True Nature ◽  
Donor And Acceptor ◽  
Structure Determinations ◽  
Self Consistent Field ◽  
Electron Donor And Acceptor ◽  
Semi Empirical

Accurate structure determinations by X-ray crystal analysis and computation using semi-empirical self-consistent field molecular orbital calculations are described and compared for five monofluorinated analogues of 4-chlorobiphenyl, i.e. 2-fluoro-4-chlorobiphenyl, 2′-fluoro-4-chlorobiphenyl, 3-fluoro-4-chlorobiphenyl, 3′-fluoro-4-chlorobiphenyl and 4′-fluoro-4-chlorobiphenyl. Intermolecular interactions for all monofluorinated isomers are dominated by phenyl–phenyl stacking and C—H–phenyl interactions. C—F bond lengths varied between 1.341 and 1.374 Å, C—Cl between 1.733 and 1.765 Å, and both correlate with electron-density differences as determined by 13C NMR shifts. The interior ring angles at ipso-fluoro substitution increase up to 122.2–124.2° due to hyperconjugation by 2p-π-orbital overlapping, a phenomenon that was also reflected in the computer calculation. The angles of C—F and C—Cl relative to the aromatic ring for vicinal fluoro- and chloro substituents show an attraction, not a repulsion, between the adjacent F and Cl substituents. This finding is explained on the basis of electron donor and acceptor properties. The dihedral angles of ortho-substituted biphenyls show that monofluoro substitution results in slightly smaller increases compared with chlorine, while additional ortho-fluorination results in little further change in the dihedral angle. In contrast, ortho-chlorination strongly decreases the co-planarity. This is likely to be due to interior ring-angle distortion and the size of the halogen substituent. Fluoro substitution does indeed affect the planarity of the PCB3 analogues, but these effects are minor compared with chloro substitution. Fluorine tagging offers promise for use in in vitro and in vivo studies. Differences in computational versus measured data emphasize the need to use a variety of methods to ascertain the true nature of the physical properties of a compound.

scholarly journals Effects of fluoro substitution on 4-bromodiphenyl ether (PBDE 3)

2008 ◽  
Vol 64 (1) ◽  
pp. 108-119 ◽  
Author(s):  
J. Klösener ◽  
D. C. Swenson ◽  
L. W. Robertson ◽  
G. Luthe
Keyword(s):  
Biological Effects ◽  
Diphenyl Ether ◽  
Environmental Pollutants ◽  
Torsion Angles ◽  
Bond Lengths ◽  
Structure Activity ◽  
Self Consistent Field ◽  
Semi Empirical ◽  
Van Der Waals Radii ◽  
Persistent Environmental Pollutants

It is our hypothesis that fluoro substitution provides a powerful tool to modulate the desired characteristics and to increase the specificity of studies of structure–activity relationships. 4-Bromodiphenyl ether (PBDE 3) and its five corresponding monofluorinated analogues (F-PBDEs 3) have been synthesized and fully characterized (using 1H, 13C and 19F NMR spectroscopy, and mass spectrometry). The accurate structure from X-ray crystal analysis was compared with iterative calculations using semi-empirical self-consistent field molecular-orbital (SCF-MO) models. The compounds studied were 4-bromodiphenyl ether (PBDE 3), the 13C6-isotopically labeled PBDE 3 (13C6-PBDE 3) and 2-fluoro-4-bromodiphenyl ether (3-2F), 2′-fluoro-4-bromodiphenyl ether (3-2′F), 3-fluoro-4-bromodiphenyl ether (3-3F), 3′-fluoro-4-bromodiphenyl ether (3-3′F), and 4′-fluoro-4-bromodiphenyl ether (3-4′F). Solid-state intermolecular interactions for PBDE 3 and the F-PBDEs 3 isomers are dominated by weak C—H(F,Br)...π and C—H...F interactions. The C—F bond lengths varied between 1.347 (2) and 1.362 (2) Å, and the C4—Br bond length between 1.880 (3) and 1.904 (2) Å. These bond lengths are correlated with electron-density differences, as determined by 13C shifts, but not with the strength of the C—F couplings. The interior ring angles of ipso-fluoro substitution increased (121.9–124.0°) as a result of hyperconjugation, a phenomenon also predicted by the calculation models. An attraction between the vicinal fluoro and halo substituents (observed in fluoro substituted chlorobiphenyls) was not observed for the bromo substituted F-PBDEs. The influence of a fluoro substituent on the conformation was only observable in PBDEs with di-ortho substitution. Calculated and observed torsion angles showed a positive correlation with increasing van der Waals radii and/or the degree of substitution for mono- to tetra-fluoro, chloro, bromo and methyl substitutions in the ortho positions of diphenyl ether. These findings utilizing F-tagged analogues presented here may prove fundamental to the interpretation of the biological effects and toxicities of these persistent environmental pollutants.

Theoretical Studies of Nonbenzenoid Hydrocarbons: 16 π-Electron Systems

1971 ◽  
Vol 49 (17) ◽  
pp. 2840-2849 ◽  
Author(s):  
F. W. Birss ◽  
N. K. Das Gupta
Keyword(s):  
Molecular Orbital ◽  
Molecular Orbital Calculations ◽  
Theoretical Studies ◽  
Electron Systems ◽  
Consistent Field ◽  
Resonance Energies ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Semi Empirical

Hückel and self-consistent-field semi-empirical π-electron molecular orbital calculations on pentalenoheptalene are reported and the results compared to those of pyrene, acepleiadylene, napth[cde]azulene, and cyclohept[bc]acenaphthylene which contain the same number of π electrons. Resonance energies of all molecules calculated by the methods of Dewar and Whitehead are reported. It is suggested that pentalenoheptalene can be treated as two fused azulene nuclei.

Submerged upflow biotower operation and computer simulation

1994 ◽  
Vol 30 (11) ◽  
pp. 143-146
Author(s):  
Ronald D. Neufeld ◽  
Christopher A. Badali ◽  
Dennis Powers ◽  
Christopher Carson
Keyword(s):  
Computer Simulation ◽  
Benzoic Acid ◽  
Computer Model ◽  
Rate Constants ◽  
Batch Mode ◽  
Operational Conditions ◽  
First Order ◽  
Low Concentrations ◽  
Biological Transformation ◽  
Kinetics Of

A two step operation is proposed for the biodegradation of low concentrations (< 10 mg/L) of BETX substances in an up flow submerged biotower configuration. Step 1 involves growth of a lush biofilm using benzoic acid in a batch mode. Step 2 involves a longer term biological transformation of BETX. Kinetics of biotransformations are modeled using first order assumptions, with rate constants being a function of benzoic acid dosages used in Step 1. A calibrated computer model is developed and presented to predict the degree of transformation and biomass level throughout the tower under a variety of inlet and design operational conditions.

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