Effect of reaction medium on the radical polymerization and copolymerization of potassium and sodium p-styrenesulphonate

The kinetics of the homogeneous free radical polymerization of potassium p-styrenesulphonate and sodium p-styrenesulphonate (SSS) in water-salt, water-dioxane, water-dimethyl sulphoxide (DMSO), DMSO—dioxane mixtures and copolymerization of SSS with acrylamide in water-salt and water-DMSO mixtures have been investigated. The overall rate of the process, the kinetic orders with respect to monomer and initiator, overall activation energy and also the properties of the resulting polymers (molecular weight, copolymer composition and compositional inhomogeneity) depend on the nature of the reaction medium. It is mainly connected with the influence of ionic strength (due to varying ionogenic monomer concentration, addition of salts and also the change of the conversion degree) and with the influence of the polarity of solvent on the rate constants for propagation and termination. The chemical and physical characteristic of the reaction mainly influence parameters of the electrostatic interactions in the system “macroradical-counterions-anions of monomer”. This leads to conformational variation of polymer chains and influences the reactivities of growing macroradicals and ionogenic monomers in polymerization and copolymerization. Data on conductivity and viscometric measurements confirmed the dependence of the conformation of polymer and copolymer macromolecules upon the composition of the medium.     

Kinetics of the polymerization of potassium p-styrenesulphonate in various media

The free radical polymerization of potassium p-styrenesulphonate has been investigated at 70° for solutions in dimethyl sulphoxide (DMSO)-water mixtures (1:3 and 3:1) and in DMSO using 2,2′-azobisisobutyronitrile as initiator. The kinetic orders with respect to monomer and initiator increase but the rate of polymerization, the value of $\text{k}{}_{\mathrm{p}}\text{/k}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{t}}$ and the average molecular weight of the resulting polymer decrease with increasing DMSO concentration in the DMSO-water mixture. These effects have been attributed to changing of parameters of the electrostatic interactions in the system “macroradical-counterions-anions of monomer” with change of composition of the medium.     

A contribution to the use of tetravalent manganese in solutions of sulfuric acid as an oxidimetric reagent

The preparation of solutions of manganese(IV) sulfate in 9 M sulfuric acid as well as the stability of these solutions was studied for 0.00501 M concentration of manganese(IV) ions. Potentiometric titration of solutions of primary standard substances, potassium iodide and sodium hexacyanoferrate, was recommended for determining the titer of 0.005 M reagent solutions. It was verified that manganese(IV) sulfate can be used for determining low concentrations of organic substances by direct titration determination of hydroquinone, p-aminophenol, and metol and by indirect determination of oxalic acid.     

Dissociation constants for the zinc(II)-8-hydroxyquinoline complexes in aqueous and sodium dodecyl sulfate micellar solutions

The constants of dissociation of 8-hydroxyquinoline (pK ₁ and pK ₂) and of its complexation with zinc ions (logβ₁, logβ₂) in sodium nitrate aqueous solutions at 293 K were calculated by modeling potentiometric titration data. The values of logβ were obtained under conditions such that the complexes occurred simultaneously in the solution and at optimum values of the ionic strength and the ratio between the metal and ligand concentrations. The apparent constants of dissociation of 8-hydroxyquinoline and of its complexation with zinc ions in a 0.01 M sodium dodecyl sulfate solution were calculated. An increase in pK and logβ was explained by the stabilization of the different forms of the ligand and its complexes in the surfactant micellar phase.     

Micellar-mediated shifts of ionization constants of amino acids and peptides

The acid-base dissociation constants, K_a, of amino acids and small peptides were determined in both aqueous and micellar solutions of sodium dodecyl sulfate and cetyltrimethylammonium bromide by potentiometric and chromatographic means. The observed differences in pK_a values between micellar media and aqueous solutions ranged between 0.23 and 2.21 units. The micellar-mediated pK_a shifts can be attributed to different solute-micelle interactions, mainly hydrophobic and electrostatic forces. The implications of the change in acid-base behavior on separation selectivity in micellar liquid chromatography and micellar electrokinetic capillary chromatography are discussed.     

Assemblies of amphiphilic compounds over rigid polymers: 2. Interaction of sodium dodecylbenzenesulfonate with chitosan-scleraldehyde gels

Gels based on chitosan cross-linked with scleraldehyde were prepared. The swelling behavior due to pH variation and to equilibration with solutions of sodium dodecylbenzene-sulfonate (SDBS) or sodium p-toluenesulfonate (p-STS) was investigated. Binding isotherms and the solubilization of Sudan III by gels equilibrated with SDBS were also determined. Gel collapse was at a SDBS concentration one order of magnitude smaller than the critical micelle concentration and was accompanied by moderately cooperative binding with K equal to 4120 M⁻¹. Binding of p-STS, which is characterized by a similar value of K but much smaller cooperativity parameter, was not accompanied by gel collapse. The formation of micelle-like aggregates of SDBS within the gel is discussed in terms of recent theoretical and experimental results.     

Effects of uv light on dilute aqueous solutions of m- and p-nitrophenol

Circumstantial evidence derived from an exploratory study by different methods suggests that the effect of UV light on dilute aqueous solutions of m- and of p- nitrophenol is largely nitrite displacement by OH^? nucleophile from the solvent, with formation of HNO₂ in the initial stages. Dilute aqueous picric acid solutions behaved in a manner more or less similar to that of the mononitrophenols and also similar to that of its methanolic sodium methoxide solutions as has been reported in the literature. In all cases, when ultimately the aqueous solutions are decolourized, photofragmentation seems to ensue.     

A pulse polarographic investigation of parathion and some other nitro-containing pesticides

The polarographic behaviour of parathion, its major metabolites (paraoxon and p-nitrophenol), and of methylparathion, EPN and pentachloronitrobenzene has been studied over a wide pH range. Differential pulse polarography is used to differentiate between parathion, p-nitrophenol and pentachloronitrobenzene. An indirect determination of parathion in the presence of paraoxon can be based on their respective rates of hydrolysis in 0.5 M sodium hydroxide solution. The electrochemical behaviour of these compounds has also been investigated in solutions containing tetraalkylammonium salts as the supporting electrolyte.     

Détermination, à 25°C,du produit ionique des solvants mixtes acétone+eau+perchlorate de sodium

The ionic products of different mixed solvents acetone+water with sodium perchlorate have been determined by a method of standardisation using solutions of “strong” acids and bases.The evolution of pk_i is plotted in function of molar fraction of acetone and concentration of sodium perchlorate.The approximate values of the ionic product of acetone and acetone+sodium perchlorate media (0.5 M, 1 M, 2 M, 3 M) have been achieved easily by graphical extrapolation.     

Liquid Chromatographic Determination of the Composition of Thiacetarsamide Solutions

Abstract

Sodium thiacetarsamide in solution is a mixture of p-arsenosobenzamide and thiacetarsamide as determined by two reverse phase liquid chromatographic (LC) procedures with the following mobile phases: Procedure I: methanol:0.25 mM sodium phosphate and 0.0125 mM sodium ethylenediaminetetraacetic acid aqueous buffer, pH 7 (15:85); and procedure II: tetrahydrofuran:2.5 mM sodium metabisulfite and 0.5 mM phosphoric acid aqueous buffer, pH 3 (5:95). Procedure I separated p-arsenosobenzamide from unretained thiacetarsamide and degradation products. Procedure II retained and separated thiacetarsamide, p-arsenosobenzamide, and degradation products. Both procedures inhibited on-column hydrolysis of thiacetarsamide to p-arsenosobenzamide and allowed two independent estimations of the p-arsenosobenzamide content of thiacetarsamide solutions. Only p-arsenosobenzamide and unidentified degradation products were detected when sodium thiacetarsamide-p-arsenosobenzamide solutions were stored for 6 months at room temperature. However, the refrigerated solutions were composed of thiacetarsamide and p-arsenosobenzamide plus trace amounts of unidentified substances. Under strongly basic conditions, thiacetarsamide hydrolyzed to p-arsenosobenzamide, which later degraded to unknown compounds. To stabilize and maintain a relatively constant composition, sodium thiacetarsamide-p-arsenosobenzamide solutions must be refrigerated and protected from light and oxygen.     

The pKa values of N,N,N&#x27;,N&#x27;-tetrakis-(2-hydroxypropyl)ethylenediamine

Aqueous solutions of the industrially important chelating agent N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine exhibit basic properties. The proton dissociation constants were determined to be 8.99 ± 0.04 (pK₁) and 4.30 ± 0.04 (pK₂) by potentiometric titration at 25° in 0.15M sodium chloride.     

Heat capacity and density of solutions of lithium and sodium nitrates in N-methylpyrrolidone at 298.15 K

The heat capacity and density of solutions of lithium and sodium nitrates in N-methylpyrrolidone (MP) at 298.15 K are studied by calorimetry and densimetry. The standard partial molar heat capacities and volumes (C? _p,2° and V? ₂°) of LiNO₃ and NaNO₃ in MP are calculated. The standard heat capacities C? _p,i ° and volumes V? _i ° of Li⁺ and Na⁺ ions in MP at 298.15 K are determined on the basis of a proposed scale of ionic contributions of C? _p,2° and V? ₂° values. The obtained data are discussed in relation to certain features of solvation in solutions of the investigated salts.     

Interpretation of positron lifetime spectra arising from micellar solutions: Determination of the ortho-positronium diffusion coefficient in the solvent

Positron lifetime spectra arising from micellar solutions of sodium dodecylsulphate (SDS) are interpreted in terms of a classical positronium diffusion model published earlier. Unlike the generally accepted assumptions, this model results in a non-exponential ortho-positronium (o-Ps) lifetime density function. A new method is presented for the simultaneous fitting of this lifetime density function to independent lifetime spectra recorded under the same experimental conditions. Among the fit parameters D_p, the diffusion coefficient of o-Ps in the solvent (i.e. heavy water) phase is studied in detail; a detailed error analysis for D_p is also given. Provided that the mean aggregation number of SDS micelles is about 60, the published D_p values show that the diffusion coefficient of o-Ps in (heavy) water at room temperature is lower than that of small ions and molecules and the Arrhenius plot indicates a strong o-Ps localization in the solvent. The hydrodynamic radius of o-Ps is calculated from the o-Ps and micellar diffusion coefficients and from the micellar radius; it is greater than that of small ions and molecules and this can be considered as an independent indirect proof for the existence of o-Ps bubble in the (heavy) water.     

The decarboxylation and thermal stability of p-amino-salicylic acid and its salts

A survey has been given of the mechanism and kinetics of decarboxylation and thermal stability of p-aminosalicylic acid and its sodium and calcium salts in the solid state and solutions.     

Fluorimetric determination of aromatic aldehydes with 2,2'-dithiobis(1-aminonaphthalene)

A sensitive fluorimetric method for the determination of aromatic aldehydes is based on their reaction in dilute sulfuric acid with a new reagent, 2,2'-dithiobis(l-amino-naphthalene) in the presence of tri-n-butylphosphine, sodium sulfite and sodium phosphite at ambient temperature. The fluorescences produced are fairly characteristic of individual aldehydes. The method is extremely selective for aromatic aldehydes and very sensitive, especially for p-hydroxybenzaldehyde, o-methoxybenzaldehyde, p-methoxybenzaldehyde and p-tolualdehyde which can be determined at concentrations of as little as 3–5 ng ml^-1.     

Dynamic Light Scattering Characterization of a Water-Soluble Terpolymer with Vinyl Biphenyl in Unsalted and Brine Solutions

The sizes and distributions of polymer chains and associating aggregates, hydrophobic associations, and apparent viscosities were investigated with dynamic light scattering (DLS), fluorescence spectroscopy and viscometry for the hydrophobically associating terpolymer poly[acrylamide(AM)/vinyl biphenyl(VP)/sodium 2-acrylamido-2-methylpropane sulphonate(NaAMPS)] (PAAP) in unsalted and brine solutions. The effects of polymer, NaCl concentration, and temperature on the conformation of polymer chains and the formation of associating structures in aqueous solutions were studied. Intra- and inter-molecular hydrophobic associations were formed and the polymer chains were coiled in unsalted solutions below a critical association concentration (C _p *): 0.05 g·dL^?1, and the apparent viscosity was very low and varied slightly with polymer concentration, but a large number of large aggregates were formed because of the presence of dominant intermolecular associations above C _p *, and the apparent viscosity increased abruptly with increasing polymer concentration. The PAAP chains were comparatively expanded (R _h: 21–92 nm) in brine solutions, resulted from the simultaneous incorporation of the bulky pendant side groups, including the biphenyl and 2-acrylamido-2-methylpropane sulphonate groups. With the addition of NaCl, large associative aggregates in unsalted solutions were destroyed to form comparatively expanded mono-macromolecules and smaller aggregates. However, as the NaCl concentration was increased from to 15 to 80 g·L^?1, more large aggregates were again formed, leading to the obvious salt-thickening behavior. The variation of R _h with temperature proved that intermolecular hydrophobic association is an endothermic process.     

Semimicrodetermination of carboxylic acids in the presence of large amounts of acyl chlorides

A procedure for the semimicrodetermination of carboxylic acids in the presence of a large excess of acyl chloride is described. Acyl chloride is first reacted with m-chloroaniline. The m-chloroaniline hydrochloride and carboxylic acid are then determined sequentially by potentiometric titration with sodium hydroxide. Titrations are performed in 80–90% p-dioxane to enhance the potentiometric breaks. With 0.05 N sodium hydroxide, as little as 0.01 mM of carboxylic acid can be determined.     

Methods for the structural investigation of xanthones: Part II. Location of hydroxyl groups by ultraviolet and visible spectroscopy1

Ultraviolet spectral shifts in presence of certain additives may be used to determine the hydroxylation pattern of xanthones. Thus, 3-hydroxyxanthones are characterized by an intense band around 355 nm which appears in presence of sodium hydroxide, o- and p-Dihydroxyxanthones decompose in presence of this reagent, the reaction rate depending on the position of the substituents. While the spectra of 1-and 2-hydroxyxanthones do not suffer modification in presence of sodium acetate, 3- and 4-hydroxy groups produce typical shifts which are dependent on the presence of additional oxygen functions. The spectra of 1-hydroxy-, as well as of o-dihydroxyxanthones, are affected by the addition of aluminum chloride. 1- and 4-Hydroxy groups with unsubstituted p-positions may be detected and distinguished through the visible spectrum (350–750 nm) of the reaction product of the xanthone with 2,6-dichlorobenzoquinone chloroimide (Gibbs test). Relatively acidic hydroxyls give rise to two maxima in this region. Two maxima, even if of different relative intensity, are also obtained with o- and p-dihydroxy-, as well as with o- and p-hydroxyallylxanthones.     

Spectral analysis of naringenin deprotonation in aqueous ethanol solutions

The deprotonation of 5,7-dihydroxy-2-(4-hydroxyphenyl)chroman-4-one (naringenin) was studied in aqueous solutions of ethanol and 0.1 mol L^?1 sodium perchlorate at 25°C. The chemical species that contributed to deprotonation were evaluated together with their pure spectral characteristics and concentration profiles by some chemometric methods. The deprotonation constants assigned by pK ₁, pK ₂, and pK ₃ were determined by multivariate curve analysis of spectral data at different pcH values. The pure spectral analysis concordant with the theoretical prediction of deprotonation constants indicates that the acidity of hydroxyl groups in naringenin decreases in the order: 7-OH, 4′-OH, 5-OH. The effects of the solvent on deprotonation were analysed in terms of the linear solvation energy relationships using the model of Kamlet, Abboud, and Taft (KAT). Multiple linear regressions were aimed towards correlating the deprotonation constants with the microscopic parameters containing hydrogen-bond acidity (α), dipolarity/polarisability (π*), and hydrogen-bond basicity (β). The most significant parameter was found to be the hydrogen-bond acidity of binary mixtures.     

Rearrangement of azoxybenzocrowns into chromophoric hydroxyazobenzocrowns and the use of hydroxyazobenzocrowns for the synthesis of ionophoric biscrown compounds

The Wallach rearrangement was used as a method for preparing p-hydroxyazobenzocrown ethers starting from different azoxybenzocrowns as substrates. Synthesis of a series of p-hydroxyazobenzocrowns under modified conditions and characterization of the obtained products are presented. o-Hydroxyazobenzocrowns were identified among the products of the photochemical rearrangement of azoxybenzocrowns. Novel biscrowns were synthesized from p-hydroxyazobenzocrown ethers. The synthesized host molecules, differing in the size of the macrocycles and in the substituents in the aromatic rings, have the same dioxymethylene linkers. They were used as potential sodium or potassium ionophores in classic and miniature (screen-printed) ion-selective electrodes. The properties (tautomerism, acid–base equilibrium) of newly prepared o-hydroxyazobenzocrown ethers and their p-substituted analogs were studied using spectroscopic methods and compared.