Solvent Effect on Deprotonation Equilibria of Acids of Various Charge Types in Non-aqueous Isodielectric Mixtures of Protic Ethylene Glycol and Dipolar Aprotic N,N-Dimethylformamide at 298.15 K

Deprotonation constants of phthalic (H₂A) and biphthalic (HA⁻) acids and of mono-protonated (BH⁺) and di-protonated (BH₂²⁺) piperazine acids have been determined at 25 °C by measuring the Emf of galvanic cells comprising H⁺-sensitive glass GE(H⁺) and Ag,AgCl electrodes in non-aqueous isodielectric mixtures of protic ethylene glycol (EG) and dipolar aprotic N,N-dimethylformamide (DMF). Solvent effects on deprotonation of the acids: ∂(ΔG _diss^o)=2.303RT[p(_s K _a)−p(_R K _a)], have been dissected into transfer Gibbs energies, ΔG _t^o _, of the species involved by evaluating ΔG _t^o of the uncharged phthalic acid and base piperazine (B) from the measured solubilities of the acid and base, respectively, and using ΔG _t^o of H⁺ based on the TATB reference electrolyte assumptions, as evaluated earlier. The contributions of the different species involved in the protolytic equilibria i.e., H⁺,H₂A,HA⁻,BH₂²⁺ and BH⁺ and their respective conjugate bases HA⁻,A²⁻,BH⁺ and B have been discussed in terms of their solvation behavior as guided by the ‘acid-base’, dispersion, structural and electronic characteristics of the acid-base species and of the co-solvent molecules and binary mixtures, ignoring the Born-type electrostatic interactions on the ionic species as the solvent system is quasi isodielectric.     

Tannic acid assisted one step synthesis route for stable colloidal dispersion of nickel nanostructures

We report here a one step synthesis route for highly stable colloidal dispersion of nickel (Ni) nanostructures in ethylene glycol (EG). tannic acid (TA), a naturally occurring molecule was used as reducing as well as capping agent. Different instrumental techniques were used to characterize the end product. It has been found that the particles are pure crystalline nickel with a face-centred-cubic (fcc) structure which are uniformly distributed throughout the surface of Ni-TA complex hybrid nanostructures resulting flower-like morphology. The synthesized nanoparticles are remarkably stable for several months. It is supposed that the TA-capped Ni nanoparticles with significantly increased stability and dispersibility could be used as a novel nanoscale material in various technological applications.     

Synthesis of polystyrene/silica hybrid composites by the sol–gel method: effect of introduction of a flexible component (butyl acrylate) into the silylated polystyrene backbone

Polystyrene/silica, polystyrene–butylacrylate/silica, silylated polystyrene/silica, and silylated polystyrene–butylacrylate/silica hybrid composites were synthesized by the sol–gel method in tetrahydrofuran using HCl as catalyst and tetraethylorthosilicate as the silica precursor. The polymers were characterized by fourier transform infrared (FTIR), nuclear magnetic resonance, and gel permeation chromatography. The sol–gel mixtures were cast on glass plates and dried in air at 30°C for 72 h. The composites were characterized by FTIR, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy analysis. Silica (12.8%) could be incorporated within the silylated polystyrene–butylacrylate matrix while retaining optical transparency. These composites showed better thermal stability and water resistance in comparison to the individual polymers.

A direct route to six and seven membered lactones via γ-C(sp3)–H activation: a simple protocol to build molecular complexity

Lactones comprise a class of valuable compounds having biological as well as industrial importance. Development of a methodology to synthesize such molecules directly from readily available materials such as aliphatic carboxylic acid is highly desirable. Herein, we have reported synthesis of δ-lactones and ε-lactones via selective γ-C(sp³)–H activation. The γ-C–H bond containing aliphatic carboxylic acids provide six or seven membered lactones depending on the olefin partner in the presence of a palladium catalyst. A mechanistic investigation suggests that C–H activation is the rate-determining step. Further transformations of the lactones have been carried out to showcase the applicability of the present strategy.

Six and seven membered lactones have been synthesized directly from readily available aliphatic acids.