IR spectroscopic manifestations of hydration of poly(diphenyl sulfophthalide) during its storage

IR spectroscopy measurements show that films of poly(diphenyl sulfophthalide) (PDSP), a cardo polymer, interact with atmospheric moisture during storage at room conditions. A total of 15 absorption bands were isolated in spectra of PDSP hydrated during storage, which belong to sorbed water and hydrolysis products. A number of absorption bands (within 1500–1800 cm⁻¹ and 980–1100 cm⁻¹) were obtained by subtracting the spectrum of the film after heating from that of the initial hydrated film. At least six individual bands in the region of the O-H bond stretching vibration were isolated by decomposing a broad complex band (3700–2000 cm⁻¹) into Gaussian components. The isolated bands were tentatively assigned based on the available literature data and quantum-chemical calculations of the characteristics of a number of complexes of a diphenyl sulfophthalide model compound with water molecules. The IR spectra and energies of the hydrogen bonds formed were calculated at the B3LYP/6-311G(d, p) level. In particular, the absorption bands at 1010 and 1079 cm⁻¹ were assigned to the symmetric stretching vibrations of the S=O bonds in the −SO₃⁻ anion, the 1062-cm⁻¹ absorption band, to ν(C-OH), and the absorption bands at 3646, 3586, and 3475 cm⁻¹, to complexes of water with sulfophthalide cycles of the polymer. After a long storage, PDSP largely transforms into a polymeric oxonium salt, and its spectrum becomes similar to that of a polymeric salt prepared by alkaline hydrolysis. A general mechanism of the interaction of PDSP with water is proposed, according to which the hydrolysis of the sulfophthalide cycles (SPC) by sorbed water yields new hydrophilic groups, sulfoacid, and hydroxyl groups. A further sorption of water by the sulfoacid results in its ionization and the formation of various hydroxonium forms. Sorption and hydrolysis are reversible processes: water is desorbed and the SPC is recovered when the polymer is heated to 100–150°C, as can be judged from an increase in the intensity of the S=O bond vibrations of the sulfophthalide cycle at 1352 and 1192 cm⁻¹. The possibility of using strongly hydrated PDSP for manufacturing proton-conducting membranes is discussed.     

Alkylation of 6-Polyfluoroalkyl-2-thiouracils with Haloalkanes

Russian Journal of Organic Chemistry - The structure of 6-polyfluoroalkyl-2-thiouracils and reactivity of nucleophilic centers in their molecules were analyzed by quantum chemical calculations....     

On the mechanism for the photooxidation of aromatic azides containing a secondary N–H bond: A sequence of intramolecular transformations with the formation of heterocyclic oximes

During the photooxidation of aromatic azides containing a secondary N–H bond at the para-position, a sequence of intramolecular transformations of nitroso oxides led to the formation of heterocyclic oximes along with the corresponding nitroso and nitro compounds.     

Constructing Homodesmic Reactions for Calculating the Enthalpies of Formation of Organic Compounds

The mathematics and software of the homodesmic approach to calculating enthalpies of formation Δ_fH° of organic compounds are described. The program generates a set of independent homodesmic reactions for a studied compound, increasing the reliability of theoretical determinations of the standard enthalpy of formation. The basic steps of program construction, using the algorithm to determine the basis of homodesmic reactions for organic compounds, and calculations for the enthalpies of formation for a random test set comprising 53 CHNO-containing organic compounds of different classes are described. It is shown that the homodesmic approach provides highly reliable theoretical values of Δ_fH° virtually regardless of the quantumchemical approach that is used. The average absolute error of MAD calculations for Δ_fH° of a test set is 2.2 kJ/mol for the simple B3LYP/6-31G(d) approach and 2.1 kJ/mol for the moderately complicated M06-2X/cc-pVTZ approach, while using the complicated method of G3 calculations reduces the MAD value to 1.7 kJ/mol.     

Kinetics of radical decomposition of di(tert-butyl) trioxide

The kinetics of radical decomposition of di(tert-butyl) trioxide was studied by spectrophotometry from the consumption of an acceptor of free radicals, 2,6-di(tert-butyl)-4-methylphenol, in CFCl₃ and CH₂Cl₂ (in the latter case, in the presence of 0.1M Bu^tOOH). The activation parameters of the reaction (log(A/s ⁻¹)=14.8±1.2 and 14.1±1.6,E _a=21.6±1.4 and 20.1±1.9 kcal mol⁻¹ in CFCl₃ and CH₂Cl₂, respectively) and the probability of radical escape to the bulk (e=0.9±0.1) were determined. The known experimental and calculated values of the O−OO bond strength in trioxides were analyzed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 61–65, January, 1999.     

A Quantum-chemical study of the mechanism of formation of styrene polymerization centers under initiation by the ferrocene—benzoyl peroxide system

The mechanism of formation of free polystyrene growth radicals and radicals bound to complexes with ferrocene when polymerization was performed in the presence of the ferrocene—benzoyl peroxide initiating system was studied by quantum-chemical calculations with the use of the PRIRODA program and the PBE/3z method. The calculated structure of the charge transfer complex between ferrocene and benzoyl peroxide was in agreement with the experimental data. The calculated heat effects of possible complex decomposition reactions showed that radical formation easily occurred in the presence of the monomer only. The most favorable energetically scheme of the formation of the active centers of the complex-radical polymerization of styrene, including the intermediate formation of the ferrocene—benzoyloxy radical complex, was suggested.     

Flash photolysis study of the reactivity of isomeric forms of arylnitroso oxides toward triphenyl phosphite

The kinetics of the reactions of phenylnitroso oxide and 4-CH₃O-, 4-CH₃-, and 4-Br-phenylnitroso oxides with triphenyl phosphite was studied in acetonitrile, benzene, and hexane by flash photolysis. The reaction occurs only with the trans-isomers of nitroso oxides. The value of the reaction rate constant increases with an increase in the electron-withdrawing power of substituents on the nitroso oxide aromatic ring, with the rate constant being almost the same in benzene and acetonitrile, and increasing by a factor of 2–3 in hexane. The temperature dependence for the decay rate constants of isomeric nitroso oxides in the presence of triphenyl phosphite was studied in acetonitrile.     

The pKa theoretical estimation of C―H,N―H,O―H and S―H acids in dimethylsulfoxide solution

A scheme for the pK_a estimation of organic acids in dimethylsulfoxide (DMSO) solution based on quantum chemical calculations is proposed. The procedure of pK_a calculation requires several steps. The first is the calculation of the gas phase acidity of the compound. The G3MP2B3, G4MP2 as well as CBS‐QB3 composite methods made it possible to estimate values of gas phase acidities of an extensive set of structures with a high confidence level (standard deviations equal to 1.15, 1.13 and 1.29 kcal mol^?1, respectively; the test set included 91 compounds). The second step is the computation of the solvation correction with the integral equation formalism version of polarizable continuum model (IEF‐PCM)–B3LYP/6‐311+G(d,p) approximation. Within the bounds of our approach, the medium properties were covered only by the PCM model, i.e. the proposed procedure neglects specific interactions between DMSO and the solute. It was determined that the approach to pK_a estimation mentioned above is the most balanced in terms of accuracy, resource intensity and computation time cost. In the third step, the error of the pK_a calculation was decreased by correlation allowances. Correlation allowances were determined for each acid class (62 С―Н, 55 N―Н, 24 O―Н and 5 S―Н acids) in the range of 50 units in terms of logarithmic scale using the test set including 146 compounds. Seven O―H acids showing the ability to form cyclic dimers were separated into a discrete group. The proposed methodology was applied to the estimation of pK_a for trans‐ and cis‐dimethyl‐4,5‐dihydro‐3H‐pyrazol‐3,5‐dicarboxylates as well as for 5‐fluorouracil subject to competitive dissociation, the latter by N1―H or N3―H bonds. Copyright © 2014 John Wiley & Sons, Ltd.