Effects of Solvents and the Structure of Amines on the Rates of Reactions of α,β-Unsaturated Nitriles and Amides with Secondary Amines

The kinetics of reactions between ,-unsaturated compounds (UCs) (acrylonitrile (AN), acryl-amide (AA), and methacrylamide (MAA)) and secondary amines (As) (piperidine, morpholine, diethanolamine, diethylamine, and dipropylamine) in water, as well as in DMF, DMSO, formamide, and 1,4-dioxane for acrylonitrile, was studied. It was found that w= k[HC]₀[A]₀for all of the test pairs. Viscosity, permittivity, and solvation characteristics, such as solvent polarity, nucleophilicity, and electrophilicity, were taken into account in considering the solvent effect on the overall reaction rate. The electrophilicity (acidity) of a medium was found to exert the greatest effect on the reaction rate. It is believed that an increase in the electrophilicity is favorable for the rapid protonation of the UC–amine intermediate complex. The effects of amine basicity, ionization potential, and dipole moment and the steric parameters of substituents in amine molecules on the rates of reactions between the unsaturated compounds and secondary amines were considered.     

Solvent effects in the reaction between piperazine and benzyl bromide

The reaction between piperazine and benzyl bromide was studied conductometrically and the second order rate constants were computed. These rate constants determined in 12 different protic and aprotic solvents indicate that the rate of the reaction is influenced by electrophilicity (E), hydrogen bond donor ability (α) and dipolarity/polarizability (π*) of the solvent. The LSER derived from the statistical analysis indicates that the transition state is more solvated than the reactants due to hydrogen bond donation and polarizability of the solvent while the reactant is more solvated than the transition state due to electrophilicity of the solvent. Study of the reaction in methanol, dimethyl formamide mixtures suggests that the rate is maximum when dipolar interactions between the two solvents are maximum.     

Solvatochromic parameters for binary mixtures of an ionic liquid with various protic molecular solvents

Abstract  Solvatochromic parameters (E _T ^N, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) have been determined for binary mixtures of propan-2-ol, propan-1-ol, ethanol, methanol and water with recently synthesized ionic liquid (IL; 2-hydroxyethylammonium formate) at 25 °C. In all solutions except aqueous solution, E _T ^N values of the media increase abruptly with the ILs mole fraction and then increase gradually to the value of pure IL. A synergistic behavior is observed for the α parameter in all solutions. The behavior of π* and β are nearly ideal for all solutions except for solutions of methanol with the IL. The applicability of nearly ideal combined binary solvent/Redlich–Kister equation was proved for the correlation of various solvatochromic parameters with solvent composition. The correlation between the calculated and the experimental values of various parameters was in accordance with this model. Solute–solvent and solvent–solvent interactions were applied to interpret the results. Graphical Abstract  Predicted values of solvatochromic parameters (SP) (E _T ^N, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) from the correlation equations versus its experimental values for binary mixtures of 2-hydroxyethylammonium formate with water, methanol, ethanol, propan-1-ol and propan-2-ol.      

The Solvent-Like Nature of Silica Particles in Organic Solvents

 Kamlet-Taft’s α (hydrogen bond donor acidity) and π^* (dipolarity/polarizability) values of various silica batches measured in various solvents are presented. The α and π^* parameters for the various solid acids are analyzed by means of Fe(phen)₂(CN)₂ (cis-dicyano-bis-(1,10)-phenanthroline-iron(II), 1), Michler’s ketone (4,4′-bis-(dimethylamino)-benzophenone, 2), and two hydrophilic derivatives of 2, (4-(dimethylamino)-4′-(di-2-hydroxyethyl)-amino-benzophenone (3a) and 4,4′-bis-(di-(2-hydroxyethyl)-amino)-benzophenone (3b) as well as coumarin 153 (4) as solvatochromic surface polarity indicators. Apparent β (hydrogen bond acceptor basicity) parameters for bare silica have been evaluated by means of an aminobenzodifuranone dye (5) as solvatochromic probe. The chemical interpretation of the α and π^* parameters and the nature of the solvent/surface interaction which they reflect are discussed. It can be shown that an increase of the HBA (hydrogen bond accepting) capacity of the solvent significantly decreases the HBD (hydrogen bond donating) capacity of the surface environment, whereas the dipolarity/polarizability value of the silica/solvent interface is a composite of many effects. The classification of the polarity of silica particles in organic solvents compared to pure liquids is outlined.     

The Solvent-Like Nature of Silica Particles in Organic Solvents

Summary.   Kamlet-Taft’s α (hydrogen bond donor acidity) and π^* (dipolarity/polarizability) values of various silica batches measured in various solvents are presented. The α and π^* parameters for the various solid acids are analyzed by means of Fe(phen)₂(CN)₂ (cis-dicyano-bis-(1,10)-phenanthroline-iron(II), 1), Michler’s ketone (4,4′-bis-(dimethylamino)-benzophenone, 2), and two hydrophilic derivatives of 2, (4-(dimethylamino)-4′-(di-2-hydroxyethyl)-amino-benzophenone (3a) and 4,4′-bis-(di-(2-hydroxyethyl)-amino)-benzophenone (3b) as well as coumarin 153 (4) as solvatochromic surface polarity indicators. Apparent β (hydrogen bond acceptor basicity) parameters for bare silica have been evaluated by means of an aminobenzodifuranone dye (5) as solvatochromic probe. The chemical interpretation of the α and π^* parameters and the nature of the solvent/surface interaction which they reflect are discussed. It can be shown that an increase of the HBA (hydrogen bond accepting) capacity of the solvent significantly decreases the HBD (hydrogen bond donating) capacity of the surface environment, whereas the dipolarity/polarizability value of the silica/solvent interface is a composite of many effects. The classification of the polarity of silica particles in organic solvents compared to pure liquids is outlined. Theoretical E _T(30) values of the solid/solvent interfaces are calculated by applying linear solvation energy (LSE) relationships using the independently measured α and π^* values of the solid acids according to Received February 2, 2001. Accepted (revised) March 3, 2001     

Solvatochromic studies on the hydrogen-bond donating and dipolarity/polarizability properties of the polyethylene oxide/silica interface

The polarity of the polyethylene oxide(PEO)/silica interface in 1,2-dichloroethane as solvent is classified by means of linear solvation energy (LSE) relationships . The properties of the bare silica particle surface and the silica/PEO interface is expressed by two terms: the dipolarity/polarizability (π*) of the interface and the hydrogen-bond donating ability (α) of the surface silanols. These terms can be defined by using the Kamlet–Taft solvent parameters α and π* as a reference system. The interfacial polarity parameters α and π* were calculated by means of correlation analyses of the energy of the UV/vis absorption maxima of the surface polarity indicators: di-cyano-bis(1,10-phenanthroline) iron II, bis-4,4′-(N,N-dimethylamino) benzophenone, and 2,6-diphenyl-4-(2,4,6-triphenyl-N-pyridino)phenolate when adsorbed onto the PEO/silica particle surface. The experimental values of the E _T(30) parameter of the PEO/silica interface are compared with independently calculated values employing specific LSE relations derived for well-behaved regular solvents and functionalized silicas. PEO adsorption on silica causes a decrease in the value of the α parameter of the silica surface and an evident increase in the dipolarity/polarizability of the interface. Received: 16 December 1998 Accepted in revised form: 8 January 1999     

Solvatochromic parameters for binary mixtures of an ionic liquid with various protic molecular solvents

Abstract  

Solvatochromic parameters (E _T ^N, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) have been determined for binary mixtures of propan-2-ol, propan-1-ol, ethanol, methanol and water with recently synthesized ionic liquid (IL; 2-hydroxyethylammonium formate) at 25 °C. In all solutions except aqueous solution, E _T ^N values of the media increase abruptly with the ILs mole fraction and then increase gradually to the value of pure IL. A synergistic behavior is observed for the α parameter in all solutions. The behavior of π* and β are nearly ideal for all solutions except for solutions of methanol with the IL. The applicability of nearly ideal combined binary solvent/Redlich–Kister equation was proved for the correlation of various solvatochromic parameters with solvent composition. The correlation between the calculated and the experimental values of various parameters was in accordance with this model. Solute–solvent and solvent–solvent interactions were applied to interpret the results.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXX.1 Correlation Analysis of Solvation Effects in Heterolysis of tert-Butyl Chloride

Quantitative analysis of the effect of solvent parameters on the rate of heterolysis of tert-butyl chloride was performed; the reaction rate is fairly described by the polarity, polarizability, and electrophilicity parameters or by the ionizing ability parameter, while the nucleophilicity of the solvent has no rate effect. A negative effect of nucleophilic solvation was revealed in protic solvents.     

Synthesis of two new chloro derivatives of the guaianolide grossmisin and the crystal structure of one derivative

The reaction of grossmisin (8α-hydroxyachillin,1) with chlorine in benzene afforded a mixture of products. The less polar product readily crystallized after chromatography. According to the X-ray diffraction data, this product has the structure of 1α,10β-dichloro-1,10-dihydrogrossmisin. The second chloro derivative of grossmisin,viz., 8β-chloroachillin, was prepared in good yield by the reaction of lactone1 with PCl₅ in CHCl₃ in the presence of Py. Published inIzvestiya Akademii Nauk Seriya Khimicheskaya, No. 11, pp. 1932–1934, November, 2000.     

Solvent effects on kinetics of an heteroatomic nucleophilic substitution reaction in ionic liquid and molecular solvents mixtures

Rate constants, k _A, for the aromatic nucleophilic substitution reaction of 2-chloro-3,5-dinitropyridine with aniline were determined in different compositions of 2-propanol mixed with hexane, benzene, and 2-methylpropan-2-ol and 1-ethyl-3-methylimidazolium ethylsulfate ([Emim][EtSO₄]) with dimethyl sulfoxide at 25°C. The obtained rate constants of the reaction in pure solvents are in the following order: 2-methylpropan-2-ol > dimethyl sulfoxide > 2-propanol > hexane > benzene > [Emim][EtSO₄]. Molecularmicroscopic solvent parameters corresponding to the selected binary mixtures were utilized to study the kinetics of a nucleophilic substitution reaction in order to investigate and compare the effects of the solvents on a chemical process. The influence of solvent parameters including normalized polarity (E _T ^N ), dipolarity/polarizability (π*), hydrogen bond donor acidity (α), and hydrogen bond acceptor basicity (β) on the second-order rate constants were investigated and multiple linear regressions gave much better results with regard to single parameter regressions. The dipolarity/polarizability of media has a positive effect in all mixtures regarding zwitterionic character of the reaction intermediate and the hydrogen bond acceptor basicity of the solvent by stabilizing of activated complex increases the reaction rate.     

Regularities in the Distribution of Substituted,Branched, and Unsaturated Carboxylic Acids Between Organic and Aqueous Phases

There is no linear correlation between the physicochemical characteristics of carboxylic acids, their pK _a in particular, and their distribution constants K _d in the diethyl ether-water system; a certain correlation with molar volume V _m was revealed. Better results were obtained with use of multiparameter equations including V _m, polarity, polarizability, and pK _a of the acids. For 14 branched and substituted carboxylic acids it was found that their distribution constants between organic and aqueous phases are described by linear multiparameter equations, polarity and basicity of the extractants being the determining factors. The coefficients of the polarity and basicity terms vary in parallel with the corresponding characteristics of the acids.     

The influence of medium on optical rotation of propylene oxide and polypropylene oxide

Specific light rotation (α) by solutions of propylene oxide and polypropylene oxide shows a complex dependence on medium properties. For propylene oxide, α values depend on medium basicity and polarizability, which increase α, and the ability to electrophilic solvation, which decreases α. With polypropylene oxide, α values are only determined by solvent polarizability.     

Investigation of the reaction of peroxide radicals derived from di-n-butyl ether withp-phenylenediamine by kinetic spectrophotometry

The kinetics of consumption ofp-phenylenediamine (PDA) in di-n-butyl ether (BE) subjected to oxidation was measured by following the accumulation of the product of the transformation of PDA. The effective rate constant of the reaction of peroxide radicals derived from BE (RO₂) with PDA was measured (k ₇ = 2·10⁴ L mol^–1 s-1) by the inhibitor method, Evidence confirming the formation of a stable complex of RO₂, with PDA were obtained. This leads to retardation of oxidation without the formation of hydroperoxides of BE (ROOH) in the acts of chain termination on PDA.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 12, pp. 2902–2903, December, 1996.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XLII. Effect of Aprotic Solvent on the Rate of 3-Methyl-3-chloro-1-butene Dehydrochlorination. Correlation Analysis of Solvation Effects

The kinetics of 3-methyl-3-chloro-1-butene dehydrochlorination in propylene carbonate, γ-butyrolactone, sulfolane, acetone, MeCN, PhNO₂, PhCN, PhCOMe, MeCOEt, cyclohexanone, o-dichlorobenzene, PhCl, PhBr, 1,2-dichloroethane, dioxane, and AcOEt were studied; v = k[C₅H₉Cl], E1 mechanism. The reaction rate is satisfactorily described by the parameters of the polarity, electrophilicity, and cohesion of the solvent; the solvent nucleophilicity and polarizability exert no effect on the reaction rate.     

Chemiluminescent imaging analysis of interferon alpha in serum samples

Enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase (HRP)-catalyzed fluorescent reaction, and oxalate chemiluminescence imaging analysis have been combined to develop a sensitive, simple, and rapid method for analysis of interferon alpha (α-IFN) in human serum samples. A typical “sandwich type” immunoassay was used. Reaction of o-phenylenediamine (OPD) with hydrogen peroxide (H₂O₂), catalyzed by HRP, produced 2,3-diaminophenazine (PDA), which was detected by chemiluminescence imaging analysis with the bis(2,4,6-trichlorophenyl)oxalate (TCPO)–H₂O₂–glyoxaline–PDA chemiluminescent system. The TCPO chemiluminescent imaging system is more sensitive and the chemiluminescence quantum yield is at least five times higher than for the luminol–H₂O₂–HRP–PIP (p-iodophenol) chemiluminescent imaging system. The results showed there was a very good linear correlation between response and amount of α-IFN in the range 1.3–156.0 pg mL⁻¹ (R = 0.9991) and the detection limit was 0.8 pg mL⁻¹ (S/N=3). The relative standard deviation (n = 9) was 4.7%. The proposed method has been used for successful analysis of the amount of α-IFN in human serum. The results obtained compared well with those obtained by conventional colorimetric ELISA and luminol chemiluminescent ELISA. Figure Procedures of the proposed method     

Do oxidations of α-diols by bis(hydrogenperiodato)argentate(III) proceed according to different rate laws?

Oxidation of α-diols, namely ethylene glycol, 1,2-propanediol, and 1,2-butanediol, by [Ag(HIO₆)₂]⁵⁻ is kinetically first-order with respect to the Ag(III) complex. The dependence of observed first-order rate constants k _obs on [α-diol] can generally be expressed by: k _obs = k _x[α-diol] + k _y[α-diol]². Our experimental results demonstrate that the different rate laws derived in the oxidation reactions of ethylene glycol (J. H. Shan et al. Chin. J. Chem. 24:478, 2006) and 1,2-butanediol (J. H. Shan et al. Transition Met. Chem. 30:651, 2005) by the Ag(III) complex are probably not correct. In turn, the reaction mechanisms based on these rate laws should probably be treated with caution.     

Kinetic studies on the dehydration of trans-dichlorotetrammine-cobalt (III) iodate dihydrate

Summary The dehydration of trans-[Co(NH₃)₄Cl₂)IO₃·2H₂O was studied isothermally by t.g.a. In the 0.1 < α < 0.8 range, where α is the fraction of the reaction complete, most of the runs gave the best fit to a second order rate law. Early stages of the reaction appear to follow a rate law based on reaction order while later stages (0.3 < α < 0.5) appear to be controlled by diffusion of H₂O. The reaction in the 0.1 < α < 0.3 range gave a best fit to a third order rate law, while the 0.3 < α < 0.5 range gave the best fit to a three dimensional control rate law. The activation energy for the overall reaction was ca. 103 kJ mol⁻¹. For α < 0.3 the activation energy was ca. 79.9 kJ mol⁻¹, but for 0.3 < α < 0.5 it was ca. 110 kJ mol⁻¹.     

Probing the dependence of the properties of cellulose acetates and their films on the degree of biopolymer substitution: use of solvatochromic indicators and thermal analysis

Although cellulose acetates, CAs, are extensively employed there is scant information about the systematic dependence of their properties on their degree of substitution, DS; this is the subject of the present work. Nine CAs samples, DS from 0.83 to 3.0 were synthesized; their films were prepared. The following solvatochromic probes have been employed in order to determine the empirical polarity, E _T(33); “acidity, α”; “basicity, β”, and “dipolarity/polarizability, π*” of the casted films: 2,6-dichloro-4-(2,4,6-triphenyl-pyridinium-1-yl) phenolate, WB; 4-nitroaniline; 4-nitroanisole; 4-nitro-N,N-dimethylaniline; 2,6-diphenyl-4-(2,4,6-triphenyl-pyridinium-1-yl)phenolate, RB. Additionally, two systems, ethanol plus ethyl acetate (EtOH–EtAc), and cellulose plus cellulose triacetate, CTA, were employed as models for CAs of different DS. Regarding the model systems, the following was observed: (i) For EtOH–EtAc, the dependence of all solvatochromic parameters on the “equivalent-DS” of the binary mixture was non-linear because of preferential solvation; (ii) The dependence of E _T(33) on equivalent DS of the cellulose–CTA films is linear, but the slope is smaller than that of the corresponding plot for CAs. This is attributed to the more efficient hydrogen bonding in the model system, a conclusion corroborated by IR measurements. The dependence of solvatochromic parameters of CAs on their DS is described by the simple equations; a consequence of the substitution of the OH by the ester group. The thermal properties of bulk CAs samples were investigated by DSC and TGA; their dependence on DS is described by simple equations. The relevance of these data to the processing and applications of CAs is briefly discussed.     

The first step of oxidation of alkylbenzenes by permanganates in acidic aqueous solutions

Data on the kinetics, kinetic isotope effects, substrate selectivety, and activation parameters for the first step of oxidation of alkylbenzenes by permanganante in acidic aqueous solutions are surveyed. The MnO₄ ⁻, HMnO₄, and MnO₃ ⁺ species serve as oxidants at different acidities. The increase in the positive charge in this series enhances the electrophilicity of the reagent, which manifests itself as an increase in the reaction rate and a change in the site of attack on the alkylbenzene molecule (either the aromatic ring or C−H bond in the alkyl group). The oxidation of the alkyl C−H bonds in alkylbenzenes and in alkanes follows similar mechanisms, while the attack on the aromatic ring proceedsvia the electrophilic aromatic substitution mechanism with a transition state intermediate between the charge transfer complex and σ-complex. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 765–780, May, 2000.     

Oxidation of steroidal diols and triols with air/NaH

Abstract  

The unusual air oxidation of steroidal triols and diols in the presence of sodium hydride in THF is described. The initial oxidation product, ketone or aldehyde, frequently undergoes further transformations in the reaction medium. The course of the reaction depends on the stereochemistry of the substrate. For example, oxidation of (20R)-20-hydroxymethyl-6β-methoxy-3α,5α-cyclopregnane-16β,17α-diol with air/NaH afforded 6β-methoxy-23,24,25,26,27-pentanor-3α,5α-cyclofurostane-16α,17α-diol in 60% yield whereas similar reaction of (20R)-20-hydroxymethyl-6β-methoxy-3α,5α-cyclopregnane-16α,17α-diol gave 6β-methoxy-D-homo-16a-oxa-3α,5α-cycloandrostan-16-one in 30% yield. The objective of this preliminary study was to select alcohols susceptible to air/NaH oxidation and to establish the effect of conditions on the course of the reaction.