Linear free energy relationship in complex reaction: Tungsten(VI) catalyzed perborate oxidation of S‐Phenylmercaptoacetic acids

Tungsten(VI) catalyzes perborate oxidation of S‐phenylmercaptoacetic acid. The catalyzed oxidation is first order with respect to the oxidant, independent of [H⁺], and displays Michaelis–Menten dependence on [PhSCH₂COOH] and [W(VI)]. The reaction requires time for equilibration between the oxidant and the catalyst. Oxodiperoxotungsten(VI) (WO(O₂)₂) is the probable oxidizing species, and decomposition of PhSCH₂COOH WO(O₂)₂ complex is rate limiting. At low [PhSCH₂COOH] and fixed [W(VI)], the oxidation follows a second order rate law. Operation of the linear free energy relationship in the oxidation has been tested with a few electron withdrawing and a few electron donating substituents. At high temperature, electron‐withdrawing groups decelerate and electron releasing groups accelerate the oxidation, the variation in rate with the substituent is in conformity with the Hammett equation. But at low temperature, electron donating substituents fail to accelerate the oxidation. The results are rationalized. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 675–681, 1999     

Lack of Linear Free Energy Relationships in the p-Toluenesulfonic Acid Mediated Chromium(VI) Oxidation of Organic Sulfides

Summary.  The oxidation of methylphenyl sulfide by imidazolium dichromate in acetonitrile mediated by p-toluenesulfonic acid is first order in IDC and TsOH and zero order in MeSPh in the concentration range studied. The IDC oxidation of 14 para-, meta-, and ortho-substituted phenylmethylsulfides at 20–45°C conforms to the isokinetic relationship but not to any of the linear free energy relationships; the isokinetic temperature lies within the experimental temperature range. Received April 18, 2000. Accepted (revised) July 12, 2000     

Influence of Alkylaluminium Activators and Mixtures thereof on Ethylene Polymerization with a Tridentate Bis(imino)pyridinyliron Complex

The effect of various alkylaluminium compounds and their mixtures on ethylene polymerization catalyzed with a tridentate bis(imino)pyridinyliron catalyst is studied. Triethylaluminium and trihexylaluminium are good cocatalysts but yield polyethylenes with broad molar mass distribution (MMD) whereas triisobutylaluminium, a less efficient activator, gives polyethylenes with unimodal and narrow MMD. Specific mixtures of branched and linear alkylaluminium compounds yield highly active catalytic systems and polyethylenes with unimodal and tunable MMD.

SEC traces of PE prepared with iron catalyst and (1) TEA, (2) TiBA, and (3) THA (Al/Fe = 250) as cocatalysts.     

Preliminary Insight of Pyrrolylated-Chalcones as New Anti-Methicillin-Resistant Staphylococcus aureus (Anti-MRSA) Agents

Bacterial infections are regarded as one of the leading causes of fatal morbidity and death in patients infected with diseases. The ability of microorganisms, particularly methicillin-resistant Staphylococcus aureus (MRSA), to develop resistance to current drugs has evoked the need for a continuous search for new drugs with better efficacies. Hence, a series of non-PAINS associated pyrrolylated-chalcones (1–15) were synthesized and evaluated for their potency against MRSA. The hydroxyl-containing compounds (8, 9, and 10) showed the most significant anti-MRSA efficiency, with the MIC and MBC values ranging from 0.08 to 0.70 mg/mL and 0.16 to 1.88 mg/mL, respectively. The time-kill curve and SEM analyses exhibited bacterial cell death within four hours after exposure to 9, suggesting its bactericidal properties. Furthermore, the docking simulation between 9 and penicillin-binding protein 2a (PBP2a, PDB ID: 6Q9N) suggests a relatively similar bonding interaction to the standard drug with a binding affinity score of −7.0 kcal/mol. Moreover, the zebrafish model showed no toxic effects in the normal embryonic development, blood vessel formation, and apoptosis when exposed to up to 40 µM of compound 9. The overall results suggest that the pyrrolylated-chalcones may be considered as a potential inhibitor in the design of new anti-MRSA agents.     

Hydrothermal synthesis of highly crystalline nanotubes/nanoplates of pure and silver-doped anatase-titania using acid-catalyst-modified sol–gel precursors

Journal of Sol-Gel Science and Technology - Highly crystalline nanotubes/nanoplates of pure and Ag-doped anatase-titania (TiO2) having high aspect-ratio have been synthesized, without the...     

Field measurement of wheel—rail impact force at insulated rail joint

Experimental Techniques - When wheels pass over insulated rail joints (IRJs) a vertical impact force is generated. The ability to measure the impact force is valuable as the force signature helps...     

Simulated mixed absorbers and effective atomic numbers for γ attenuation

The total γ-ray interaction cross-sections on mixed absorbers were determined at 662 keV with a view to study the effective atomic numbers for γ-ray absorption under narrow beam good geometry set-up. The measurements were taken for the combination of metallic absorbers like aluminium, copper, lead and mercury and also for the simulated absorbers by rotating the targets. ORTEC HPGe and NaI(Tl) detectors were used for detection of γ-rays. The experimental results compare favourably with theoretical values derived from XCOM package and suggest the usefulness of the concept of effective atomic numbers and the utility of the rotating absorbers technique.     

Linear free energy relationships in the chromium(VI) oxidation of sulfides in acetonitrile

The oxidation of 14 para-, meta-, and ortho-substituted phenyl methyl sulfides with isonicotinium dichromate in acetonitrile, brought out by p-toluenesulfonic acid, follows a common mechanism, conforms to the isokinetic relationship but not to any of the linear free energy relationships; the isokinetic temperature lies in the experimental temperature range.