Kinetics and mechanism of the reaction of benzyl bromide with copper in dimethylacetamide in the presence of oxygen

The reaction of copper metal with benzyl bromide in dimethylacetamide in the presence of oxygen has been studied. Oxidative dissolution of copper follows the single-electron transfer mechanism with formation of benzaldehyde, benzyl alcohols, and copper(II) coordination compounds. The kinetic and thermodynamic parameters of the process have been determined by resistometry. Intermediately formed species have been identified and quantitated, and the reaction stereochemistry has been studied. The reaction mechanism is discussed.     

Kinetic study of Berthelot reaction steps in the absence and presence of coupling reagents

Several reaction steps in the Berthelot reaction for the determination of ammonia have been separately studied. A reaction order of two has been confirmed for the reaction between HOCl and NH(3). The rate constant for this reaction has been determined to be 3.2 x 10(6)l.mole(-1).sec(-1). The first evidence for the formation of benzoquinonechlorimine is presented. Pentacyanoferrate coupling reagents which accelerate the production of indophenol have been found to operate on the reaction between NH(2)Cl and phenol. The rate constant for the final step of the reaction sequence has been determined to be 5.3 x 10(-3)l.mole(-1).sec(-1). A reaction between chlorimine and pentacyanoferrate compounds has been found to be responsible for the formation of a green product in the presence of excess of coupling reagent.     

Determination of azo compounds with N-bromosuccinimide in acetic acid medium

The bromination reaction of azo compounds with N-bromosuccinimide in acetic acid medium has been studied. Some reaction products have been isolated and reaction mechanisms suggested. The reaction study has been applied for the determination of 2-10 mg of azo compounds. The maximum deviation of the results from the theoretical value is generally within +/- 1%.     

Kinetics and mechanism of the production of higher olefins from stearic acid in the presence of an alumina-supported nickel sulfide catalyst

A nickel sulfide catalyst which efficient in the decarbonylation of fatty acids to olefins and dienes has been obtained for the first time by treating alumina-supported nickel sulfate with hydrogen, and its properties have been studied. In its presence, the olefin selectivity of the reaction can exceed 90%. The kinetics of stearic acid deoxygenation to heptadecenes has been investigated, a kinetic model has been constructed, and a mechanism has been proposed for the reaction over this catalyst. Olefin oligomerization is the dominant side reaction. Kinetic evidence for the catalytic inhibition of oligomerization by nickel hydrides formed on the catalyst has been obtained. The compositions of active site–reactant adsorption complexes have been discussed.     

Magnesium(II) and cadmium(II) octaphenyltetraazaporphyrinates in metal exchange reaction with MnCl<Subscript>2</Subscript> in DMSO

Reaction kinetics of metal exchange of Mg(II) and Cd(II) octaphenyltetraazaporphynates with MnCl₂ in DMSO has been studied by spectrophotometry. Kinetic parameters of the metal exchange reaction have been determined. Possible stoichiometric reaction mechanism has been suggested. Effect of solvent and salt solvate nature on the rate of metal exchange reaction has been revealed.     

A study on a photochemical reaction in the system N,N-dimethylaniline-bromobenzene

The UV radiation absorbed by N,N-dimethylaniline dissolved in bromobenzene has been found to initiate a photochemical reaction. Resulting products were identified and a modified mechanism of the reaction has been suggested. To support the mechanism, quantum yields for the formation of some of the reaction products have also been determined.     

Kinetics of aquation of chloropentamminecobalt(III) perchlorate in ethylene glycol-water media

Summary The aquation of chloropentamminecobalt(III) ion has been studied in ethylene glycol-water mixtures up to 80% by weight at five temperatures from 35 to 55°C. Specific solvent effects on the reaction rate and mechanism have been investigated and discussed. The validity of our previously proposed equations, correlating the specific reaction rate with the dielectric constant of the medium has been examined. The thermodynamic parameters of activation have been calculated and presented as evidence for the solvation effects and in support of the proposed reaction mechanism.     

Catalytic reactions in emulsions in the presence of a polymeric catalyst

The theory of reactions between a surface-active substrate and a polymeric catalyst in emulsions has been developed. The conditions under which the rate of reaction in such systems substantially surpasses the rate of reaction in homogeneous systems have been determined and the regimes that make it possible to reduce the total time of the process have been established.     

Reaction of (Ac)Co-5,15di(ortho-methyloxyphenyl)-2,8,12,18-tetramethyl-3,7,13,17-tetrabutylporphyrin and its molecular complex with organic peroxides in xylene

The reaction of cobalt porphyrinate with organic peroxides in o-xylene has been studied using spectrophotometric titration, and its kinetic parameters have been determined. Imidazole has been shown to influence the process rate. A comparative analysis of the kinetic parameters of peroxide decomposition involving cobalt(III) porphyrinate and its zinc analogue has been carried out. A PM3 quantum-chemical method was used to optimize discrete molecules of the reagents and reaction intermediates, and their geometric parameters have been derived. Steric hindrances in the cobalt porphyrinate macrocycle and a considerable enhancement of distortion have been noticed to occur upon its reaction with a peroxide molecule.     

Temperature vs. time sequences to palliate deactivation in parallel and in series-parallel with the main reaction: parametric study

The calculation of temperature vs. time sequences to palliate catalyst deactivation in an integral reactor has been studied either by maintaining constant the conversion at the reactor outlet in a simple reaction or by maintaining constant the concentration of a given component at the outlet in a complex reaction system. The experimental systems studied, which are a simple one (dehydration of 2-ethylhexanol) and a complex one (isomerization of cis-butene), have kinetic models of the Langmuir-Hinshelwood-Hougen-Watson type for the main reaction and deactivation, with deactivation by coke dependent on the concentration of the reaction components. In the reaction of dehydration of 2-ethylhexanol deactivation occurs in parallel with the main reaction and in the isomerization of cis-butene deactivation occurs in series-parallel with the main reaction. A parametric study has been carried out for both reaction systems. The sequences calculated have been experimentally proven in an automated reaction apparatus.     

A catalytic method for the determination of trace osmium in continuous flow and flow injection systems

A procedure has been developed for the determining osmium using a catalytic indicator reaction of arsenic(III) oxidation with potassium bromate and neutral red in continuous flow and flow injection systems. The possibilities of the flow systems have been compared on an example of the proposed reaction, and the regularities of this reaction conducted in different flow systems have been revealed. Recommendations on the choice of the optimal variant of the flow system are given. The accuracy of the procedure has been confirmed by the results of determining osmium in a State Reference Sample.     

Mechanism of the thermal dehydrochlorination of poly(vinyl chloride) models in the liquid phase

The thermal dehydrochlorination of model compounds of PVC has been investigated in the liquid phase in an inert atmosphere. Electrophilic catalysis and the effect of various solvents on this reaction have been studied. It has been found that the electron-accepting power of the reaction medium is the decisive rate-determining factor, while the dielectric constant comes second. A mechanism of thermal dehydrochlorination has been suggested, in which a reaction between the substrate and the proton giving rise to the carbonium ion is the rate-determining step for the whole process.     

MNDO study of reaction paths: Hydroboration of methyl cyanide

The hydroboration reaction of methyl cyanide has been investigated by the MNDO method. It has been shown that the reaction requires an activation energy of 25.3 kcal/mol and involves a four-center-like transition state in the rate-determining step. This reaction has been compared with the corresponding reaction of hydrogen cyanide, and the effect of methyl substitution on the reaction has been discussed. The charge-transfer effects accompanying the reaction have also been studied.     

Mechanism of oxygen transfer in the epoxidation of an olefin by molecular oxygen in the presence of an aldehyde

[reaction: see text] The reaction pathway for peroxide-initiated aldehyde-mediated oxidation of olefins to epoxides by molecular oxygen has been studied. The pathways of reaction via a peroxy acid or an acyl peroxy radical have been differentiated by investigation of the reaction of 4 with oxygen to provide 6 via 8.     

Metal exchange reaction of magnesium octaphenyltetraazaporphyrin with copper,cobalt, and zinc chlorides in DMSO and DMF

Metal exchange reaction of (octaphenyltetraazaporphyrinato)magnesium(II) with copper, cobalt, and zinc chlorides in dimethyl sulfoxide and dimethylformamide has been studied by spectrophotometry. Kinetic and thermodynamic parameters of the process have been determined, and a probable reaction mechanism has been proposed. Zinc(II), copper(II), cobalt(II), and cobalt(III) complexes of octaphenyltetraazaporphyrin have been isolated and characterized.     

氮杂偶联加成反应的研究

氮杂偶联加成反应是一类在近十年里才受到重视的原子经济性新反应, 尤其是在近几年里许多有效的合成方法不断被发展和研究. 系统总结了各种氮源参与的氮杂偶联加成反应的研究进展.     

Synthesis of pallescensin-E : Use of crown ether in the Wadsworth procedure for olefin formation

The furanosesquiterpene, pallescensin-E has been prepared by a route involving reaction of a dimethyl 3-furylmethyl phosphonate anion with 2,3-dimethylbenzaldehyde in the presence of 15-crown-5; this reaction has been shown to have general applicability.     

Temperature oscillations in bromate–gallic acid system: A calorimetric study

The oscillatory reaction between potassium bromate and gallic acid in sulfuric acid medium has been studied calorimetrically with and without ferroin indicator. Enthalpy changes during oscillations have increased with increasing bromate concentration in presence and absence of the indicator. Prominent catalytic activity of the indicator has been observed. An initial large enthalpy change has been observed in both uncatalyzed and catalyzed conditions prior to the starting of oscillation. Attempts have been made to correlate the main thermal events with the proposed mechanism of the reaction. © 1995 John Wiley & Sons, Inc.     

Training the old dog new tricks: the applications of the Biginelli reaction in polymer chemistry

Recently, the Biginelli reaction, one of the most famous multicomponent reactions, has been introduced into the polymer chemistry to highly efficiently synthesize some interesting functional polymers. In this mini-review, several applications of the Biginelli reaction in polymer chemistry have been summarized, including polycondensation, post-polymerization modification, one-pot synthesis of well-defined polymer, etc. Meanwhile, the utilization of the Biginelli reaction in material science and chemical biology, and the future development of the Biginelli reaction in polymer chemistry have also been discussed.     

The model of 1,3-dipolar cycloaddition reaction of 4,5-dihydro-1H-imidazole 3-oxide derivatives with alkynes

The influence of solvents and different structural factors on the rate of 1,3-dipolar cycloaddition reaction of the 4,5-dihydro-1H-imidazole 3-oxide derivatives with alkynes have been studied. Nitrones and alkynes have been ranged by their relative activity in this reaction. Using the DFT calculation with the triple zets basis set, the energy profile of the reaction has been plotted, and the structures and energy characteristics of the transition states have been determined. The mechanism of this reaction has been shown to be concerted and asynchronous. The validity of the used computational approach for the detailed investigation of 1,3-dipolar cycloaddition of nitrones has been demonstrated.