Polyelectrolytes in thin liquid films

The review addresses the influence of polyelectrolytes on the statics and dynamics of thin liquid films. Both, changes of interfacial and bulk properties, contribute to the overall behaviour of thin films formed from aqueous polyelectrolyte solutions. Therefore, the chapter is separated into two parts: polyelectrolytes at film interfaces and polymers in film bulk.     

Synthesis of Unsymmetrical Ureas and S‐Thiocarbamates under Catalyst‐free Conditions in a [BMIM]BF4 Ionic Liquid

Unsymmetrical ureas and S‐thiocarbamates were prepared in good to excellent yields by direct condensation of phenylurea with amines and thiols in 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIM]BF₄) without the addition of any additives. The [BMIM]BF₄ ionic liquid is a mild medium and can be recycled and reused several times.     

4‐Heptanone cyclic diperoxide: Improved preparation method and solvent effect on its thermolysis in solution

Cyclic organic peroxides have interesting pharmacological properties and are used at industrial level as polyfunctional initiators of polymerization, and so their preparation through novel methods has attracted the attention of numerous researchers. White crystals of 4‐heptanone cyclic diperoxide (HDP) can be obtained in acidic media at ?1°C by a reaction between 4‐heptanone and hydrogen peroxide. Its thermal decomposition was studied in acetone, cyclohexane, acetonitrile, ethyl acetate, ethanol, 2‐propanol, 2‐butanol, and 1,4‐dioxane at temperatures higher than 120°C, showing a behavior accordingly with a pseudo‐first‐order kinetic law up to at least 80% HDP conversion. It was demonstrated that an increase in solvent polarity is accompanied by an increase in reaction rates. The effect of solvent polarity on the thermal decomposition rate constant values can be associated with a reaction mechanism involving a more dipolar‐activated complex than the diperoxide initial molecule. The activation parameters varied widely from 31.2 to 46.6 kcal mol^?1 and ?1.33 to 31.7 cal mol^?1 K^?1 when going from ethanol to cyclohexane as reaction solvents, respectively. An enthalpy–entropy compensation effect was observed in all solvents. Specific interactions between the oxygen atoms from the peroxidic bond and the hydrogen atom bonded to C2 and/or from the OH group can be taken into account to explain that the existence of the compensation effect does not mean that an isokinetic relationship consequently can be established. The kinetic results showed that an isokinetic relationship is observed only for a group of solvents. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 657–666, 2011     

Theoretical estimation of the aqueous pKas of thiols

The ionisation state of a compound is a key parameter influencing the compound's activity as a drug, metabolite, pollutant, or other active chemical agent. Sulfhydrol compounds (thiols) tend to be considerably more acidic than their hydroxyl (alcohol) analogues. In this report, quantum chemical approaches previously used for the estimation of the aqueous pK_as of alcohols are applied to the estimation of the acidities of thiols. Acidity estimates obtained from the general-purpose SPARC calculational programme (S.H. Hilal, S.W. Karickhoff, and L.A. Carreira, Quant. Struct.-Act. Relat. 14, 348 (1995)) and the ACD/Labs PhysChem Suite v12 programme package are employed as benchmarks. Quantum chemical calculations were performed using both the semiempirical RM1 method and the density functional theory B3LYP/6-31+G^* method. The effectiveness of the SM5.4 and SM8 solvent models in estimating the aqueous-phase acidities was also evaluated. All of the approaches examined demonstrated strong correlations with the experimental acidity values.     

XPS and NEXAFS studies of aliphatic and aromatic amine species on functionalized surfaces

The chemical constitution of functionalized supports is an important parameter that determines their performance in a broad range of applications, e.g. for immobilization of biomolecules. Supports with amino functionalized surfaces are also often used for DNA microarray experiments. However, spectral data which have been reported for surfaces with amino functionalities suffer from some inconsistencies. In this article a detailed XPS (X-ray photoelectron spectroscopy) and NEXAFS (Near edge X-ray absorption fine structure) database for amino functionalized surfaces is presented. Amino-terminated surfaces prepared from aliphatic and aromatic aminosilanes or aminothiols and a field sample are considered. Effects of aging in air and damage by radiation are addressed as well.     

Bonding in some covalent derivatives of the 1,2,3,4-thiatriazole-5-thiolate anion. A topological study

The study of pseudohalides has found a deep interest to nonmetal chemists for many years. Due to the similarities between the halides and the pseudohalides, the pseudohalide family of compounds is of fundamental chemical interest. The pseudohalide concept was introduced in 1925 and since its introduction, the pseudohalide principle has been used extensively in nonmetal chemistry to predict the structure and stability of many molecular species.

The so-called ‘azidodithiocarbonate’ anion, more properly referred to as the 1,2,3,4-thiatriazole-5-thiolate anion, CS2N3-, is of particular interest. In a short communication we have recently reported the topological study of some CS2N3-containing species reported by Crawford et al. Previous reports on these compounds showed that in covalent derivatives, not only does the ring remain intact but also the site of attachment of the R group is most likely at the exocyclic sulfur atom in contrast to the previously suggested N-R connectivity. Therefore, the structure and bonding of derivatives of the CS2N3- moiety is clearly an important question.

With that in our mind, we undertook a topological analysis, based on the AIM theory, to gain more insight into the bonding in covalent derivatives of CS2N3- moiety, trying to find an explanation to the origin of the NH and S-H connectivities. The question is: which is the reason that makes all the covalent derivatives prefer the S-R connectivity while the hydracid has an N-H one?     

Double photoexcitation of helium in a strong dc electric field

We report the first experimental measurements of the effect of an applied field on the photoexcitation and autoionization of doubly excited states of helium. Ground-state photoionization spectra have been measured in the region below the He+(N=2) threshold with static electric fields of up to 84.4 kV/cm across the interaction region. The results are compared to the theoretical calculations of Chung et al. [J. Phys. B 34, 165 (2001)]], which are the only calculations available in this regime. Transitions to several states in the N=2, n=6 manifold are assigned, and a wealth of new structure is observed. Our data show that many more series are mixed in by the field than those predicted by theory.     

On regular self-complementary graphs

A regular self-complementary graph is presented which has no complementing permutation consisting solely of cycles of length four. This answers one of Kotzig's questions.