Salt Effects on Aqueous Cationic/Anionic Surfactant Two‐Phase Regions

The influence of added salts (KCl, NaF, NaCl, NaBr, Na₂SO₄, Na₃PO₄) on aqueous cetyltrimethylammonium bromide (CTAB)/sodium dodecyl sulfonate (AS) two‐phase regions were studied. For KCl, the concentration dependence of salt effect on aqueous two‐phase regions was investigated. When brine substitutes pure water as a solvent, the positions of aqueous two‐phase regions in the phase diagram change. The results indicate that for aqueous two‐phase systems with excess anionic surfactant (ATPS‐A), the salt effect was mainly dependent on the cationic inorganic counterions, whereas for aqueous two‐phase systems with excess cationic surfactant (ATPS‐C), the salt effect was mainly dependent on the anionic inorganic counterions. The shift of aqueous two‐phase region is strengthened following the Hofmeister series. All the experiments were performed at 318.15 K.     

New Organic Salt from Levofloxacin-Citric Acid: What Is the Impact on the Stability and Antibiotic Potency?

This research dealt with the composition, structure determination, stability, and antibiotic potency of a novel organic salt composed of levofloxacin (LF) and citric acid (CA), named levofloxacin-citrate (LC). After a stoichiometric proportion screening, the antibiotic-antioxidant reaction was conducted by slow and fast evaporation methods. A series of characterizations using thermal analysis, powder X-ray diffractometry, vibrational spectroscopy, and nuclear magnetic resonance confirmed LC formation. The new organic salt showed a distinct thermogram and diffractogram. Next, Fourier transform infrared indicated the change in N-methylamine and carboxylic stretching, confirmed by ¹H nuclear magnetic resonance spectra to elucidate the 2D structure. Finally, single-crystal diffractometry determined LC as a new salt structure three-dimensionally. The attributive improvements were demonstrated on the stability toward the humidity and lighting of LC compared to LF alone. Moreover, the antibiotic potency of LF against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) enhanced ~1.5–2-fold by LC. Hereafter, LC is a potential salt antibiotic-antioxidant combination for dosage formulas development.     

Effects of additives on the aggregation of surfactants: binding domination

The effects of electrolytes, alcohols, and urea on the aggregation of SDS, CTAB, and TritonX-100 at 25℃ have been investigated by fluorescence probing of pyrene. Both electrolytes and alcoholsreduce the critical micelle concentration (CMC) of the ionic surfactants, while the effect of the former ismore pronounced. It is shown that the effects of electrolytes mainly depend on the concentrationsand especially the valence of the opposite charge ions, and only slightly depend on the same charge ionsin respect of ion aggregate of micelle. The logarithm of CMC is not linearly correlated with theconcentrations of the counter ion or the electrolytes. The results are rationalized in terms of Hartley'smodel. Propanol increases the CMC of TX-100, while electrolytes and urea do not. In all the threekinds of surfactant micelles the excitation spectrum of pyrene slightly red-shifts (ca. 4 nm) from thatin water, but is not affected by the additives. The micropolarity of the environment in which pyrenemolecule resides in SDS micelle decreases with the increase of the concentrations of electrolytes. Thisis not the case when alcohols and urea were added to SDS or to TX-100. It is suggested that theaddition of electrolytes would result in more orderly orientation of SDS molecules. It is the bindingstrength of the counter ions that dominates the effects of additives on the aggregation of surfactants.     

Study on the Reaction of Benzimidazolium Salt with Amine Compounds

The addition-hydrolysis reaction of benzimidazolium salt with some mono- and bifunctional amine nucleophiles is reported,and a novel method of biomimetic synthesis for formamides and heterocycle compounds is provided.     

Effects of Conjugated Systems on UV-Visible Light-sensitive D-π-A Type Sulfonium Salt Photoacid Generators

A series of D-π-A type sulfonium salt photoacid generators with different π-conjugated structures, such as triphenyl, phenylstilbene, styryl-biphenyl, and stilbene, were designed to determine the effect of molecular structures on the photochemical and photophysical properties. The mechanisms of photochemical generation of H+ were studied by UV-Vis spectroscopy, theoretical calculations, and fluorescence spectroscopy. It is found that the frontier orbits determine the absorption, the molar extinction coefficients, and the quantum yields of photoacid generation. Triphenyl systems connected with sulfonium are beneficial to increase the quantum yields of acid generation. The photoreactivity of four sulfonium salts was further evaluated through the polymerizations of various epoxide monomers at different irradiation wavelengths(365–425 nm) by using the real-time infrared spectroscopy with light-emitting diodes. The high quantum yields for acid generation(ΦH~+= ~0.32 to 0.58) and the high molar extinction coefficients(ε = ~23500 L·mol~(-1)·cm~(-1) to 31000 L·mol~(-1)·cm~(-1)) of the sulfonium salts lead to high conversion rates(over 50%–80%). Hence, these photoinitiators exhibit potential for the photocuring applications.     

“Salt in a porous matrix” adsorbents: Design of the phase composition and sorption properties

This review formulates the concept of target-oriented synthesis of two-component “salt in a porous matrix” (SPM) adsorbents designed for processes such as gas dewatering, moisture control, heat conversion in adsorption heat pumps, and equilibrium shifting in catalytic reactions. In terms of this approach, the requirements imposed on an ideal adsorbent, which is optimal for a particular application, are initially formulated; then, a material with nearly optimal properties is synthesized. Methods for the target-oriented synthesis of SPM adsorbents with the required properties are considered. The effects of the nature of the salt and the matrix, the salt content, the pore size of the matrix, and the synthesis conditions on the phase composition and adsorption properties of the SPM adsorbents are studied.     

Study of the Inclusion Complexes of β-Cyclodextrin with the Sodium Salt of Trisulfonated Triphenylphosphine

The formation of inclusion complexesbetween the sodium salt of trisulfonatedtriphenylphosphine and -cyclodextrin has beeninvestigated at two temperatures by high field nuclearmagnetic resonance, electrospray mass and UV-visspectroscopies. At 268 K, titration experiments andJob's method suggest that the major species insolution is a 1 : 1 inclusion complex. The moleculargeometry of this inclusion complex was studied usingthe ROESY NMR technique complemented by molecularmodelling. All these methods converged towards thestructure attained by inserting one aromatic ring intothe hydrophobic cavity of the host from the side ofthe secondary hydroxyls. At 298 K, a higher proportionof 2 : 1 and 3 : 1 complexes induces strong alterations ofthe NMR signals, preventing an easy and reliabledetermination of association constants. Nevertheless,an apparent association constant can be determinedfrom UV-vis data by assuming a 1 : 1 equilibrium. Thegeometry of the 2 : 1 and 3 : 1 complexes is also brieflydiscussed from ROESY NMR experiments.     

Solvent Effects on kp in Organic Media?: Statement to the Response

A recent response on a publication from our team investigating solvent effects on propagation rate coefficients is commented. Among other issues, we point to the fact that the response interprets only a subset of the data provided in our original contribution.

     

Interactions in the Protein–Zinc Salt–Organic Tanning Agent System

Russian Journal of General Chemistry - The suitability of a combined tanning system comprising zinc salts and an organic tanning agent as an alternative to chromium compounds was considered. The...     

Effects of substituents upon the P···N noncovalent interaction: the limits of its strength

Previous work has documented the ability of the P atom to form a direct attractive noncovalent interaction with a N atom, based in large measure on the charge transfer from the N lone pair into the σ* antibonding orbital of the P-H that is turned away from the N atom. As the systems studied to date include only hydrides, the present work considers how substituents affect the interaction and examines whether P···N might compete with other attractive forces such as H-bonds. It is found that the addition of electron-withdrawing substituents greatly strengthens the P···N interaction to the point where it exceeds that of the majority of H-bonds. The highest interaction energy occurs in the FH(2)P···N(CH(3))(3) complex, amounting to 11 kcal/mol. A breakdown of the individual forces involved attributes the stability of the interaction to approximately equal parts electrostatic and induction energy, with a smaller contribution from dispersion.     

Upper Rim Diester-bridged Calixarenes and Oligocalix-arenes: the Effects of the Length of Bridged Reagents on Their Distribution

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Study on the Formation of Urea or Salt Induced Vesicles in Built-system Surfactant

The spontaneous formation of vesicles in the aqueous of cationic surfactant phosphate (PTA) and anionic surfactant sodium dodecyl sulfate (SDS) at certain mixing ratios have obtained^1. The addition of urea or Nal will expand the range of spontaneous vesicle formation. The fact is demonstrated by negative-staining transmission electron microscope(TEM) and dynamic light scattering(DLS) methods. The phenomenon especially in the part of urea is reported by us at first. Mechanism of urea/Nal-induced vesicles formation is discussed from the viewpoint of the molecular geometry packing parameter f, conformation and interaction.     

Triflic Salt–Catalyzed Coupling: Iron Triflate–Catalyzed Homocoupling of Aryl Bromides in the Presence of Metallic Magnesium

In the presence of metallic magnesium, the homocoupling reaction of aryl bromides catalyzed by iron triflate was carried out readily in one pot. The catalyst was used successfully in this coupling reaction without preparation of Grignard reagent in advance. Meanwhile, the catalyst was recovered easily and reused smoothly with only a little loss of its activity.     

Studies on the Effects of Epimedium Extract on Erythrocytes

Epimedium, one of representatives of traditional Chinese herb, is mainly composed of flavones and polysaccharide. It is famous for its antioxidant, antineoplastic and antiaging activities and has been widely used in the field of invigorating kidney and st…     

Influence of a Hydrophobic Environment on the Structure of Arginine—Carboxylate Salt Bridge

The exact structure of an arginine-carboxylate salt bridge in different chemical environments remains a controversial problem.In the present work,the zwitterionic and neutral forms of arginine-carboxylate salt bridge were studied by the B3LYP/6-311G(d,p)//PM3 method.It turns out that the neutral forms are more stable than the zwitterionic coumterparts in gas phase.However,whnen bound by α-cyclodextrin,the zwitterionic forms become more stable than the corresponding neutral ones.It is suggested that the hydrophobic environment provided by the cyclodextrin cavity leads to such behavior.Therefore,the salt bridge still could be in a zwitterionic form in the hydrophobic interior of the real proteins.     

Effects of the nanoassociation of hexadecyltrimethoxysilane precursors on the sol–gel process

Modifications to the refractive indices of meso-structured organic–inorganic films caused by variations in the mole fraction of precursors in ethanolic solutions were investigated. The refractive indices were dependent on the mole fraction of C₁₆TMS (hexadecyltrimethoxysilane) and of the C₁₆TMS/TMOS (tetramethoxysilane) (1/1) mixture in ethanol. The dependency was determined to be nonlinear, and the phenomenon was attributed to self-assembly caused by the long alkyl groups (C₁₆) on the C₁₆TMS. Changes in the maximum decreasing rate of d_n/d_x values [(d_n/d_x)_max—for d_n/d_x estimation, the curves from Fig. 1 were associated with a polynomial; using a dedicated program, d_n/d_x was calculated; maximum values of d_n/d_x were taken into account and were included in Table 1)] were used to distinguish the behavior of alcoholic precursor mixtures. In the case of using pyrene as a fluorescent probe, the ratio between two peaks from the pyrene emission spectra (I₁/I₃) strongly decreased as hydrophobic micro-surroundings formed due to the self-assembly process. The UV–VIS spectra of a cationic dye solution, R6G, was studied because dilute solutions of the dye in equilibrium form measurable ratios of dimers and monomers. The absorbance was modified as micro-surroundings with different polarities were formed. These three methods demonstrated that nano-structuration was present prior to the occurrence of the sol–gel process. The combination of C₁₆TMS with other alkyltrialkoxysilane precursors having hydrocarbon chain lengths between C₁ and C₈ provided further evidence for a nonlinear dependence of the refractive indice and fluorescence spectra of pyrene. The properties of the final hybrids obtained by the sol–gel process were significantly affected by the precursor hydrocarbon chain lengths. DSC, XRD and FTIR measurements were used to show the plasticizing phenomena of C₁₆ as other alkyltrialkoxysilanes (i.e., C₁–C₈) were added.

Specific Ion Effects on the Enzymatic Degradation of Polyester Films

Soil environment on earth contains a variety of ions, which are expected to play a vital role in the biodegradation of plastics discarded in the environment. In this work, poly(butyleneadipate-co-terephthalate)(PBAT) is employed as a model biodegradable plastic to study the specific ion effects on the enzymatic degradation of polyester plastics. The results show that the specific ion effects on the enzymatic degradation rate of the PBAT films and on the catalytic rate constant for the enzymatic ...