An interesting chloride ion effect in the Heck reaction

Addition of chloride ion is found to enhance the yields of cross-couplings between aryl iodides and selected olefin acceptors.     

Iminium ion catalysis: use of the alpha-effect in the acceleration of the Diels-Alder reaction

The alpha-effect can be used in the acceleration of the Diels-Alder reaction between a series of dienes and electron deficient dienophiles using iminium ion catalysis, providing a novel molecular scaffold capable of performing this class of catalytic process.     

Reactions in microemulsion media. Nucleophilic displacement reaction of benzyl chloride with bromide ion

A kinetic and synthetic study of the reaction of benzyl chloride with bromide ion has been performed in microemulsions composed of cetyltrimethylammonium bromide, 1-butanol, water, potassium bromide, and hexane; rates and yields of benzyl bromide formation decreased with increasing hexane content.     

Photochemical estimation of mercuric chloride by Eder's reaction with ceric ion as sensitiser

Summary It has been shown that the sensitising action of ceric salts on Eder's reaction could be employed for the quantitative estimation of mercuric chloride by determining the calomel formed iodometrically. The photochemical reduction to calomel is complete in about 15 minutes.Our thanks are due to Prof. G. Gopala Rao for his interest in the work.     

Solvent effects on SN2 reaction between substituted benzyl chloride and chloride ion

The effects of solvent on S_N2 reaction between some substituted benzyl chlorides and chloride ion have been investigated by DFT and ab initio methods using the polarizabale continuum model. The activation energies are higher in the solution media relative to the gas phase and grow by the increase in the dielectric constant of solvent. The complexation energies in solution media are smaller than those in the gas phase and reduce with increasing the dielectric constant. The energy data are in good agreement with the geometrical parameters and substituent constants. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Intramolecular catalysis and cyclization in the reaction of α,ω-diaminooligomethylenes with bifunctional sulphonyl chloride. Effect of chain length on polycondensation reaction

As an elementary reaction of polycondensation reactions, rates of the reaction of 1,5-naphthalenedisulphonyl dichloride, a bifunctional fluorescent reagent, with excess α,ω-diaminooligomethylenes were measured by fluorometry in dilute solution. The rate constant, corresponding to that for the reaction of the first step of the polycondensation between the disulphonyl dichloride and the diamines, depended remarkably on the chain length of the diamines. By using 5-dimethylamino-1-naphthalenesulphonyl chloride, a monofunctional fluorescent reagent, and α-aminooligomethylenes, rates of model reactions between the monoamines and the monosulphonyl chloride, the diamines and the monosulphonyl chloride, as well as the monoamines and the disulphonyl dichloride were measured by fluorometry. The remarkable chain length dependence is explained by intramolecular catalysis by the primary amino group.     

Substituent effects on SN2 reaction between substituted benzyl chloride and chloride ion in gas phase

Nucleophilic substitution reaction between some substituted benzyl chlorides and chloride ion has been investigated by ab initio and DFT methods. New calculated energy data are in better agreement with experimental data. The electron‐withdrawing groups increase the energy barriers and the electron‐donating groups decrease them. The changes of geometrical parameters and energy data are in good agreement with the results of atoms in molecules and natural bond orbital analyses. The relationship between Hammett coefficients and energy data (and geometry parameters) has been established and the ρ constant has been calculated for this reaction. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Effect of chloride ion on the kinetics and mechanism of the reaction between chlorite ion and hypochlorous acid

The effect of chloride ion on the chlorine dioxide formation in the ClO 2 (-)-HOCl reaction was studied by following .ClO 2 concentration spectrophotometrically at pH 5-6 in 0.5 M sodium acetate. On the basis of the earlier experimental data collected without initially added chloride and on new experiments, the earlier kinetic model was modified and extended to interpret the two series of experiments together. It was found that the chloride ion significantly increases the initial rate of .ClO 2 formation. At the same time, the .ClO 2 yield is increased in HOCl but decreased in ClO 2 (-) excess by the increase of the chloride ion concentration. The two-step hydrolysis of dissolved chlorine through Cl 2 + H 2O left harpoon over right harpoon Cl 2OH (-) + H (+) and Cl 2OH (-) left harpoon over right harpoon HOCl + Cl (-) and the increased reactivity of Cl 2OH (-) compared to HOCl are proposed to explain these phenomena. It is reinforced that the hydrolysis of the transient Cl 2O 2 takes place through a HOCl-catalyzed step instead of the spontaneous hydrolysis. A seven-step kinetic model with six rate parameters (constants and/or ratio of constants) is proposed on the basis of the rigorous least-squares fitting of the parameters simultaneously to 129 absorbance versus time curves measured up to approximately 90% conversion. The advantage of this method of evaluation is briefly outlined.     

Acid catalysis in the N-bromosuccinimide-propargyl alcohol reaction

The reaction of N-bromosuccinimide (NBS) with propargyl alcohol in aqueous acidic medium is hydroxybromination. It is first order with respect to NBS, propargyl alcohol and H⁺, and inverse first order with respect to succinimide. The kinetic results point to solvated bromonium ion as the reactive species.     

Micellar catalysis in flow injection systems: the nitrosation reaction.

The use of aqueous micellar carrier streams in flow injection is shown to catalyse on-line reactions and thereby improve the sensitivity relative to non-micellar systems. The effect of several different micellar systems on the nitrosation reaction of N,N-diethylaniline in acidic solution was investigated. The mechanism of the micellar enhancement is discussed and the sensitivities of the method in both aqueous and micellar media are compared. The presence of the cationic surfactant, cetyltrimethylammonium bromide, is shown to improve the sensitivity of the analysis. The effect of the micellar solution on the dispersion characteristics of the system was also studied. The greater viscosity of the micellar phase increases dispersion for non-reacting systems, but when monitoring a reaction product the increased reaction rate can counteract this and the micellar carrier can show less over-all dispersion than the aqueous carrier.     

Stoichiometry and products of ozone reaction with chloride ion in an acidic medium

It is shown by means of direct spectrophotometry in the UV and visible ranges that the only product of the O₃ reaction with Cl⁻(aq) in an acidic medium is molecular chlorine Cl₂; in solutions, it is in equilibrium with the complex ion Cl₃⁻. It is found that the consumption of one ozone molecule corresponds to the formation of one chlorine molecule. The stoichiometric equation for the reaction is obtained.     

Cerium(III) ion catalysis in the oxalic acid-bromate reaction: Anomalous kinetic behavior of oxalic acid

The kinetics of cerium(III) ion catalyzed Br(V) oxidation of oxalic acid in the presence of HClO₄/H₂SO₄ and mercury(II)-a bromide removing ion, exhibits second order each in [br(V)] and [acid], 0.4 and zero order in [Ce(III)]. However, the kinetic behavior of oxalic acid is anomalous with –0.7, zero and 1.4 order. The chemistry underlying the phenomena is discussed.

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Br(V), Ce(III), HClO₄/H₂SO₄ (II), , [Br(V)], [], 0,4 [Ce(III)]. , , .. –0,7, 0 1,4. , .

     

Primary stage of the reaction between ozone and chloride ions in aqueous solution: Can chloride ion oxidation by ozone proceed via electron transfer mechanism?

It is found that chloride-ion oxidation by ozone via electron transfer mechanism does not occur due to its extremely high endoergicity and negligibly low rate. It is concluded that all processes supposedly associated with this reaction, particularly ozone decomposition in sodium chloride solution initiated by Cl^· atoms, do not take place either. It is shown that experimental data on the products and kinetic regularities of the interaction of O₃ with Cl⁻ contradict the assumption that the electron transfer reaction is its primary stage. In fact, chloride-ion oxidation by ozone proceeds via the mechanism of oxygen atom transfer. It is noted that in order to estimate the possibility of using an ozonated physiological saline in medicine, the formation of chloride-ion oxidation products and ozonation byproducts must be taken into account.     

离子色谱法检测酸性镀铜液中的微量氯离子

采用Na2CO3-NaHCO3为淋洗液和抑制电导检测,对酸性镀铜液中的微量氯离子进行检测。采用AgNO3作为沉淀剂使Cl-分离富集,再用Na2S2O3溶液溶解沉淀后进行检测,可以很好地消除酸性电镀液中高浓度SO4^2-的干扰。该方法线性良好,Cl^-的检出限为0.01μg/mL,回收率在98.6%-101.7%之间,由于该方法能够很好地消除大量SO4^2-的干扰,在电镀铜工业中对酸性镀铜液中氯离子的监控可发挥作用。     

The cause for tremendous acceleration of chloride substitution via base catalysis in the chloro pentaammine cobalt(III) ion

The base hydrolysis reaction of Co(NH(3))(5)Cl(2+) was investigated using density functional theory and molecular orbital methods. Geometries and energies of conjugate bases, intermediates, transition states, and minimum energy crossing points were computed. For the base hydrolysis of Co(NH(3))(5)Cl(2+), three pathways might operate: the mechanism proposed by Basolo and Pearson, the mechanism via a hexacoordinated intermediate exhibiting a triplet ground state, and a fully stereomobile I(d) mechanism. The hexacoordinated intermediate can lose the leaving ligand readily to form a square pyramidal pentacoordinated intermediate with a triplet state, which interconverts rapidly and reversibly into the Basolo-Pearson trigonal bipyramid with a singlet state. Due to its high activation energy, a stereochemical rearrangement via a Berry pseudorotation does not take place. The intermediates are not protonated because their pK(a) values are ~5 for the hexacoordinated intermediate and ~-6 for the trigonal bipyramidal pentacoordinated intermediate. The Basolo-Pearson mechanism proceeds with 50% stereoretention and 50% stereomobility. In the case that the hexacoordinated intermediate converts into the trigonal bipyramid, products with the same stereochemistry would be obtained. If, however, for the square pyramidal intermediate with a triplet state the entering ligand competes efficiently with the rearrangement into the trigonal bipyramid or if the substitution takes place at the hexacoordinated intermediate via, e.g., the I(d) mechanism, the reaction would proceed with retention of the configuration. Direct substitution via the I(d) mechanism, operating for azide and to a small extent also for water, is fully stereomobile. Computations on the Basolo-Pearson mechanism have also been performed for the chloro pentaammine complexes of chromium(III), ruthenium(III), and rhodium(III). This pathway might operate for chromium(III) but not for ruthenium(III) and rhodium(III).