Kinetic investigation on the reactions of p‐toluenesulfonyl chloride with p‐substituted benzoic acid(s) in the presence of triethylamine in aprotic solvents

Second‐order rate constants of the reactions of p‐toluenesulfonyl chloride with p‐substituted benzoic acids in the presence of triethylamine in acetonitrile/acetone under equimolar and pseudo‐first‐order conditions have been determined by the conductometric method using the Guggenheim principle at 25, 30, 35, and 40°C. The reactions follow second order with respect to the whole and first order with respect to each of the reactants. The order of reactivity of the substituents in benzoic acid is rationalized. Activation parameters are obtained by applying the usual methods. The Hammett plot has been found nonlinear, whereas the Bronsted plot shows good correlation. This may be explained on the basis of electronic effects of substituents on the reaction center. Kinetic data and the product analyses indicate that the reaction proceeds through direct nucleophilic attack on the sulfur center. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 303–308, 2009     

Micelle‐catalyzed reaction of ninhydrin with DL‐valine in the absence and presence of organic solvents

Kinetics of the DL ‐valine‐ninhydrin reaction has been studied spectrophotometrically under varying conditions of [CTAB], [ninhydrin], [DL ‐valine], pH, temperature, and %(v/v) organic solvents (solvents used: 1‐propanol, methylcellosolve, acetonitrile, and dimethyl sulfoxide). Addition of CTAB and increase in the proportion of organic solvents, both showed catalyzing effect on the reaction. The effect of simultaneous presence of CTAB and DMSO in the reaction mixture has also been seen. The rate profiles obtained for solutions containing from 10% to 70% DMSO exhibited clear maxima that shifted progressively to higher concentrations of CTAB. The experimental results are explained in terms of specific solvent effects and the formation of stoichiometric hydrate DMSO · 2H₂O and the inhibitory effect of DMSO on micelle formation. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 634–642, 2006     

Rate constants for reaction of 1,2‐dimethylimidazole with benzyl bromide in ionic liquids and organic solvents

The rate constant for the Menschutkin reaction of 1,2‐dimethylimidazole with benzyl bromide to produce 3‐benzyl‐1,2‐dimethylimidazolium bromide was determined in a number of ionic liquids and molecular organic solvents. The rate constants in 12 ionic liquids are in the range of (1.0–3.2) × 10^?3 L mol^?1 s^?1 and vary with the solvent anion in the order (CF₃SO₂)₂ N^? < PF₆^? < BF₄^?. Variations with the solvent cation (butylmethylimidazolium, octylmethylimidazolium, butyldimethylimidazolium, octyldimethylimidazolium, butylmethylpyrrolidinium, and hexyltributylammonium) are minimal. The rate constants in the ionic liquids are comparable to those in polar aprotic molecular solvents (acetonitrile, propylene carbonate) but much higher than those in weakly polar organic solvents and in alcohols. Correlation of the rate constants with the solvatochromic parameter E _T(30) is reasonable within each group of similar solvents but very poor when all the solvents are correlated together. Better correlation is obtained for the organic solvents by using a combination of two parameters, π* (dipolarity/polarizibility) and α (hydrogen bond acidity), while additional parameters such as δ (cohesive energy density) do not provide any further improvement. © 2004 Wiley Periodicals, Inc. *

1 This article is a US Government work and, as such, is in the public domain of the United States of America.

Int J Chem Kinet 36: 253–258, 2004     

Effects of mixed aqueous‐organic solvents on the rate of intramolecular carboxylic group‐catalyzed cleavage of N‐(4′‐methoxyphenyl)phthalamic acid

Kinetic study on the cleavage of N‐(4′‐methoxyphenyl)phthalamic acid (NMPPAH) in mixed H₂O‐CH₃CN and H₂O‐1,4‐dioxan solvents containing 0.05 M HCl reveals the formation of phthalic anhydride (PAn)/phthalic acid (PA) as the sole or major product. Pseudo first‐order rate constants (k₁) for the conversion of NMPPAH to PAn decrease nonlinearly from 60.4 × 10^?5 to 2.64 × 10^?5 s^?1 with the increase in the contents of 1,4‐dioxan from 10 to 80% v/v in mixed aqueous solvents. The rate of cleavage of NMPPAH in mixed H₂O‐CH₃CN solvents at ≥50% v/v CH₃CN follows an irreversible consecutive reaction path: NMPPAH PA. The values of k₁ are larger in H₂O‐CH₃CN than in H₂O‐1,4‐dioxan solvents. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 316–325, 2004     

Hydrogen‐bonded structures of the isomeric compounds of quinoline with 2‐chloro‐5‐nitrobenzoic acid, 3‐chloro‐2‐nitrobenzoic acid, 4‐chloro‐2‐nitrobenzoic acid and 5‐chloro‐2‐nitrobenzoic acid

The structures of four isomeric compounds, all C₇H₄ClNO₄·C₉H₇N, of quinoline with chloro‐ and nitro‐substituted benzoic acid, namely, 2‐chloro‐5‐nitrobenzoic acid–quinoline (1/1), (I), 3‐chloro‐2‐nitrobenzoic acid–quinoline (1/1), (II), 4‐chloro‐2‐nitrobenzoic acid–quinoline (1/1), (III), and 5‐chloro‐2‐nitrobenzoic acid–quinoline (1/1), (IV), have been determined at 185 K. In each compound, a short hydrogen bond is observed between the pyridine N atom and a carboxyl O atom. The N...O distances are 2.6476 (13), 2.5610 (13), 2.5569 (12) and 2.5429 (12) Å for (I), (II), (III) and (IV), respectively. Although in (I) the H atom in the hydrogen bond is located at the O site, in (II), (III) and (IV) the H atom is disordered in the hydrogen bond over two positions with (N site):(O site) occupancies of 0.39 (3):0.61 (3), 0.47 (3):0.53 (3) and 0.65 (3):0.35 (3), respectively.     

Rhodium-catalyzed reaction of thiols with polychloroalkanes in the presence of triethylamine

[reaction: see text] RhCl(PPh(3))(3) catalyzes a reaction of thiols with polychloroalkanes in the presence of triethylamine. This reaction serves as a convenient new method to produce formaldehyde dithioacetals, ethylenedithioethers, thioformates, and dithiocarbonic esters under mild conditions.     

Hydrogen‐bonded structures of the isomeric compounds of phthalazine with 3‐chloro‐2‐nitrobenzoic acid, 4‐chloro‐2‐nitrobenzoic acid and 4‐chloro‐3‐nitrobenzoic acid

The structures of three isomeric compounds, C₇H₄ClNO₄·C₈H₆N₂, of phthalazine with chloro‐ and nitro‐substituted benzoic acid, namely, 3‐chloro‐2‐nitrobenzoic acid–phthalazine (1/1), (I), 4‐chloro‐2‐nitrobenzoic acid–phthalazine (1/1), (II), and 4‐chloro‐3‐nitrobenzoic acid–phthalazine (1/1), (III), have been determined at 190 K. In the asymmetric unit of each compound, there are two crystallographically independent chloronitrobenzoic acid–phthalazine units, in each of which the two components are held together by a short hydrogen bond between an N atom of the base and a carboxyl O atom. In one hydrogen‐bonded unit of (I) and in two units of (II), a weak C—H...O interaction is also observed between the two components. The N...O distances are 2.5715 (15) and 2.5397 (17) Å for (I), 2.5655 (13) and 2.6081 (13) Å for (II), and 2.613 (2) and 2.589 (2) Å for (III). In both hydrogen‐bonded units of (I) and (II), the H atoms are each disordered over two positions with (N site):(O site) occupancies of 0.35 (3):0.65 (3) and 0.31 (3):0.69 (3) for (I), and 0.32 (3):0.68 (3) and 0.30 (3):0.70 (3) for (II). The H atoms in the hydrogen‐bonded units of (III) are located at the O‐atom sites.     

Effect of solvent on the free energy of activation of S_N2 reaction between phenacyl bromide and amines

The kinetics of SN2 reaction between phenacyl bromide and various amines in 12 different solvents were studied. Solvent effects on the rate of this reaction and free energy of activation, ΔG# , were interpreted by applying the Abraham-Kam-let-Taft (AKT) equation. UK solvent polarity (π1*), solvent hydrogen-bond basicity (β1) and Hildebrand cohesive density energy (δH2) are those parameters which increase the rate constant and decrease ΔG# , while solvent hydrogen-bond acidity (α1) will have the compensatory effect. A comparison among obtained values of second rate constants, k2, for different amines in a given solvent indicates that the amine reactivities are highly dependent on their structures. The consequent decrease of the rate constant for different amines in any given solvent was found to be: primary > secondary> tertiary. This order results from steric effects of amines.     

One‐pot synthesis of linear and branched poly(amide aspartimide)s with good solubility in organic solvents

Linear and branched poly(amide aspartimide)s were prepared through the reaction of 4,4′‐diaminodiphenylmethane with 4‐maleimidobenzoic acid and 5‐maleimidoisophthalic acid, respectively. The synthesis was performed through a one‐pot operation by means of the Michael addition reaction between amine and maleimide groups and the dehydration condensation reaction between amine and carboxylic acid groups. The obtained polymers exhibited fairly good solubility in aprotic polar solvents at room temperature and in pyridine, tetrahydrofuran, acetone, and chloroform upon heating. High glass‐transition temperatures (≥225 °C) and thermal stability above 360 °C were found for the polymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1923–1929, 2005     

New efficient reaction media for SET‐LRP produced from binary mixtures of organic solvents and H2O

SET‐LRP is mediated by a combination of solvent and ligand that promotes disproportionation of Cu(I)X into Cu(0) and Cu(II)X₂. Therefore, the diversity of solvents suitable for SET‐LRP is limited. SET‐LRP of MA in a library of solvents with different equilibrium constants for disproportionation of Cu(I)X such as DMSO, DMF, DMAC, EC, PC, EtOH, MeOH, methoxyethanol, NMP, acetone and in their binary mixtures with H₂O was examined. H₂O exhibits the highest equilibrium constant for disproportionation of Cu(I)X. The apparent rate constant of the polymerization exhibits a linear increase with the addition of H₂O. This is consistent with higher equilibrium constants for disproportionation generated by addition of H₂O to organic solvents. Furthermore, with the exception of alcohols and carbonates, the rate constant of polymerization in binary mixtures could be correlated with the Dimroth‐Reichardt solvent polarity parameter. This is consistent with the single‐electron transfer mechanism proposed for SET‐LRP that involves a polar transition state. These experiments demonstrate that the use of binary mixtures of solvents with H₂O provides a new, simple and efficient method for the elaboration of a large diversity of reaction media that are suitable for SET‐LRP even when one of the two solvents does not mediate disproportionation of Cu(I)X. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5577–5590, 2009     

Effect of molecular oxygen on the kinetics and mechanism of the reaction of 2-bromo-1-ethylpyridinium bromide with triethylamine in acetonitrile

The nucleophilic aromatic substitution of bromine into 2-bromo-1-ethylpyridinium bromide (I) in its reaction with triethylamine (II) is accompanied by subsequent oxidation of the intermediates by molecular oxygen dissolved in acetonitrile. The following reaction products were identified: 1-ethyl-2-pyridone, triethylamine N-oxide, and the hydrobromide salt of triethylamine. The reaction kinetics was studied with reagents ratios     

Effect of solvation on the structure conformation of human serum albumin in aqueous–alcohol mixed solvents

In the present paper, we analyze the effect of ethanol in the structure conformation of human serum albumin (HSA) by far- and near circular dichroism, UV–Vis spectroscopy and density and ultrasound velocity measurements. Both circular dichroism and absorbance data show changes in both tertiary and secondary structures at ethanol concentrations below 30% (v/v), which can be indicative of the presence of an equilibrium intermediate state. At higher ethanol concentrations in the mixed solvent (>30% (v/v)), a change from a rich--helix to a β-sheet and unordered secondary structure is observed. Moreover, it seems that certain protein aggregation starts to occur. From ethanol concentrations higher than 55% (v/v), a certain redissolution of these aggregates takes place, which seems to be accompanied by an increase in -helix content. Trends found by volume and compressibility determinations seem to be in accordance. Both volume and compressibility increase with alcohol concentration up to 50% (v/v) but in two well-defined steps indicating a different nature of these two changes, the first of them with a variation close to that shown by a molten globule intermediate state. Moreover, at ethanol concentrations higher than 55% (v/v), a decrease in both quantities occurs confirming the breakdown of protein aggregates.     

Solvent extraction of thorium(IV) with dibutyldithiophosphoric acid in various organic solvents

The extraction of thorium(IV) from perchlorate solutions with di-n-butyldithiophosphoric acid (HBudtp) in various organic solvents occurs through an ion exchange mechanism. The extracted species in the organic phase is an eight-coordinate complex Th(Budtp)₄. The higher values of the distribution ratio obtained in HBudtp-benzene-water system than in HBudtp-n-butanol-water system are explained by higher solubility of the complex species in nonpolar solvents. The position of the extraction curves in the pH-range lower than 0.7 reduces the complexation of thorium(IV) with Budtp^– in the aqueous phase and also the hydrolysis process.     

Effect of binary block‐selective solvents on self‐assembly of ABA triblock copolymer in dilute solution

We have studied the self‐assembly of the ABA triblock copolymer (P4VP‐b‐PS‐b‐P4VP) in dilute solution by using binary block‐selective solvents, that is, water and methanol. The triblock copolymer was first dissolved in dioxane to form a homogeneous solution. Subsequently, a given volume of selective solvent was added slowly to the solution to induce self‐assembly of the copolymer. It was found that the copolymer (P4VP₄₃‐b‐PS₃₆₆‐b‐P4VP₄₃) tended to form spherical aggregate or bilayer structure when we used methanol or water as the single selective solvent, respectively. However, the aggregates with various nanostructures were obtained by using mixtures of water and methanol as the block‐selective solvents. The aggregate structure changed from sphere to rod, vesicle, and then to bilayer by changing water content in the block‐selective solvent from 0 to 100%. Moreover, it was found that the vesicle size could be well controlled by changing the copolymer content in the solution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1536–1545, 2008     

Solubilities of cinnamic acid esters in binary mixtures of ionic liquids and organic solvents

The solubilities of three cinnamic acid esters, namely, methyl ferulate, methyl p-coumarate, and methyl sinapate, have been measured in mixed solvent systems of tert-butanol with 1-butyl-3-methyl-imidazolium hexafluorophosphate ([BMIM][PF₆]), 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIM][BF₄]) and 1-methyl-3-octyl-imidazolium tetrafluoroborate ([OMIM][BF₄]) at 303.15 and 321.15 K, and in mixed solvent systems of ethyl acetate with [BMIM][BF₄] and [OMIM][BF₄] at 303.15 K. In eight cases, out of the 22 data sets, an additive behaviour of the solubility was observed, positive deviations from additivity were observed in six cases, a positive synergistic effect in five cases, and, finally, negative deviations from additivity in the remaining three cases. Prediction of the solubilities of the solutes in the various ternary systems was performed with the NRTL and UNIQUAC activity coefficient models. The binary interaction parameters of the models between solute and solvent molecules were taken from the literature. When the parameters between the solvent molecules are fitted to literature data, satisfactory predictions are not always obtained. On the other hand, very good predictions are obtained when only one of the two interaction parameters between the two solvent molecules is fitted to one single point of the solubility isotherm and the other interaction parameter is set equal to zero.     

(N‐Heterocyclic carbene)Pd(triethylamine)Cl2 as precatalyst for the synthesis of Poly(triarylamine)s

The use of a highly active, air‐, and moisture‐stable N‐heterocyclic carbene‐palladium(II) complex for the polymerization of anilines and aryl dibromides or dichlorides by Buchwald‐Hartwig coupling is presented. In comparison to previous catalytic systems, higher molecular weight polymers with improved yields were obtained in shorter reaction times. The first examples of fabrication of OFETs with polytriarylamines synthesized with aryl dichlorides and anilines are also presented. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4904–4911     

Importance of steric effect and evaluation of quantitative structure reactivity relationship (QSRR) in the quaternization reaction of benzothiazoles and phenacyl bromide

The kinetics of reaction of substituted 2-aminobenzothiazoles and phenacyl bromide have been followed conductometrically and in some cases, argentometrically. Both the methods produced almost the same rate constants. Substituents at position 5 of the benzothiazole nucleus behave like para substituents of the benzene ring. A correlation with Hammett σ_p substituent constants has been obtained with a rho value of ?1.04. The rate data of quaternization reaction of 4, 5, and 6 substituted 2-aminobenzothiazoles with phenacyl bromide have been correlated with F_k, R_k, and V_w values by multiple regression analysis with the equation suggested by Williams and Norrington and modified by us. The values are found to correlate well with the equation, log k = ?4.4979 ? 0.4815f_jF_k + 0.5933r_jR_k ? 0.0277V_w.     

Kinetic study of the nitrosation of 1,3‐dialkylureas in aqueous‐perchloric acid medium

The kinetics of the nitrosation of 1,3‐dimethyl (DMU), 1,3‐diethyl (DEU), 1,3‐dipropylurea (DPU), 1,3‐dibuthyl (DBU), and 1,3‐diallylurea (DAU) were studied in a conventional UV/vis spectrophotometer in aqueous‐perchloric acid media. The kinetic study was carried out using the initial rate method. The reaction rate observed was where K_a is the acidity constant of nitrous acid. The diureas exhibited the reactivity order DMU ? DEU > DPU > DAU, which can be interpreted as a function of the steric impediment generated by the R alkyl group in the rate controlling step. A probable relationship between both the chemical reactivity and structure of the nitrosable substrate with the biological activity of the N‐nitroso compounds generated is proposed. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 273–279, 2004