Silica gel-mediated hydrohalogenation of unactivated alkenes using hydrohalogenic acids under organic solvent-free conditions

Silica gel-mediated hydrochlorination of unactivated alkenes using 35% hydrochloric acid under organic solvent-free conditions proceeded to give the corresponding chlorides in good yields. Hydrobromination or hydriodination using 47% hydrobromic acid or 55% hydriodic acid afforded the corresponding halides, respectively. Silica gel could be recycled five times without any significant loss of activities.     

Synthesis and structural characterization of Pd(II) thiosemicarbazonato complex: Catalytic evaluation in synthesis of diaryl ketones from aryl aldehydes and arylboronic acids

A simple route to synthesize triphenylphosphinopalladium(II) thiosemicarbazonato complex has been described. Elemental analysis, spectral (IR, NMR) and single crystal X-ray diffraction techniques were employed for the complete characterization of the complex. The latter was found to be effective catalyst for carbon–carbon cross-coupling reaction of aryl- and heteroarylboronic acids with aromatic and heteroaromatic aldehydes to form the corresponding diaryl ketones. The influence of reaction parameters such as solvent, base, reaction temperature and catalyst loading was also investigated.     

Proton transfer rate‐equilibria in apolar aprotic solvents: a historical perspective

Low dielectric constant apolar aprotic solvents, although employed on a limited scale for studying proton transfer reactions as compared with commonly used polar protic or dipolar aprotic ones, offer some particular advantages, namely, specific solute–solvent interactions are virtually eliminated and proton transfer occurs directly in an apolar aprotic solvent. An intriguing feature of these reactions is their general acid‐catalyzed/base‐catalyzed kinetics with a time scale over microseconds to minutes. In fact, the true or intrinsic relative strengths of acids/bases when measured in such solvents come to the fore much more clearly than those obtained in other classes of solvents. Recently, a review documenting the post‐1980 developments relating to proton transfer reactions in apolar aprotic solvents has been published. The present article is a commentary of the pre‐1980 developments in this area since the 1920s Brønsted–Lowry's “proton cult” of acid–base theory. Copyright © 2016 John Wiley & Sons, Ltd.     

A di‐tert‐butyl acrylate monomer for controlled radical photopolymerization

A new di‐tert‐butyl acrylate (diTBA) monomer for controlled radical polymerization is reported. This monomer complements the classical use of tert‐butyl acrylate (TBA) for synthesis of poly(acrylic acid) by increasing the density of carboxylic acids per repeat unit, while also increasing the flexibility of the carboxylic acid side‐chains. The monomer is well behaved under Cu(II)‐mediated photoinduced controlled radical polymerization and delivers polymers with excellent chain‐end fidelity at high monomer conversions. Importantly, this new diTBA monomer readily copolymerizes with TBA to further the potential for applications in areas such as dispersing agents and adsorbents. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 801–807     

Oxidative amidation of benzyl alcohols with amino acid esters mediated by N-hydroxysuccinimide/phenyliodine diacetate

A simple protocol involving metal-free oxidative amidation of benzyl alcohols with amino acid esters has been presented. The amidation proceeds in a radical pathway unlike in conventional metal-mediated extrusion of dihydrogen. The method is advantageous in terms of metal-free conditions, nonexpensive commercial starting substrates. Also various substituents in the starting materials are tolerated and sterically hindered amino acid side chains could provide good yields of amide products.     

Synthesis and properties of cross-linkable DNA duplex using 4-amino-2-oxo-6-vinyl-1,3,5-triazine

We synthesized the DNA oligonucleotide containing a new cross-linkable 4-amino-2-oxo-6-vinyltriazine (AOVT) nucleobase analogue (Et-AOVT) and evaluated these properties. Our results of the cross-link assay and thermal denaturing assay of duplexes containing AOVT demonstrated that the additional aza of AOVT has an impact on the duplex stability and crosslink properties. Our data suggests that the additional 5-aza of AOVT is involved in the hydrogen bonding with the complementary guanine, and this hydrogen bonding system successfully flipped the reactive vinyl group out to the major groove of the duplex demonstrating a new paradigm of a “cross-linkable duplex”.     

Imidazolium Based Surface Active Ionic Liquids as Novel Micellar Media for Simultaneous and Sensitive Electrochemical Detection of Dopamine and Ascorbic Acid

Surface active ionic liquid (SAIL) micelle assisted, simultaneous and highly sensitive electrochemical sensing of dopamine (DA) and ascorbic acid (AA) is presented. Results presented herein establish that SAILs viz.1‐dodecyl‐3‐methyl imidazolium chloride ([DDMIM][Cl]), 1‐octyl‐3‐methyl imidazolium chloride ([OMIM][Cl]) and 1‐butyl‐3‐methyl imidazolium chloride ([BMIM][Cl]) exhibit a probe and SAIL nature/concentration specific impact on the redox behaviour of hydroquinone (H₂Q), dopamine (DA) and ascorbic acid (AA). To our observations, the electrochemical behaviour of DA and AA is affected oppositely by SAILs with the apparent effects being more appreciable in presence of [DDMIM][Cl]. In the presence of [DDMIM][Cl] micelles, the electro‐oxidation of AA was observed to occur at potentials about 350 mV less positive than required for electrooxidation of DA, an important advantage that minimises the interference of former in sensing of the later. The peak to peak potential separation of 350 mV observed in presence of [DDMIM][Cl] micelles is the largest to be reported so far. The DPV signal for DA and AA displayed a linear response in the concentration range of 6.6 to 99.9 μM and 6.6 to 131.5 μM respectively. Very low detection limits of 0.0161 μM for DA in presence of 39.8 μM AA and 0.0227 μM for AA in presence of 39.8 μM DA were estimated in micellar phase of [DDMIM][Cl].     

A combined experimental and DFT investigation of the adsorption of humic acid by-products on polypyrrole

This study sheds light on the removal of humic acid by-products (trimellitic and pyromellitic acids; TMA and PMA, respectively) from aqueous solution using conducting polypyrrole (PPy) as an effective adsorbent. The effects of experimental factors including contact time, solution pH, initial concentration, adsorbent dose, and temperature were systematically investigated. The pseudo-second-order kinetic model provides the best correlation with adsorption experimental data. The equilibrium adsorption was well described by the Langmuir model with maximum mono-layer adsorption capacities of 47.62 and 71.43?mg?g^?1 for TMA and PMA, respectively. The analysis of thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic in nature. In addition, we investigated the adsorption mechanism using the density functional theory (DFT) calculations. The TMA and PMA were physisorbed on the PPy surface through the formation of hydrogen bonds between carboxylic groups of adsorbate molecules and the amino group of the adsorbent. The calculated theoretical data were in good agreement with experiments.     

Synthesis of 5-[(2-hydroxynaphthalen-1-yl)diazenyl]isophthalic acid and its application to electrocatalytic oxidation and determination of adrenaline,paracetamol, and tryptophan

In this study,Au nanoparticles/poly 5-[(2-hydroxynaphthalen-l-yl)diazenyl]isophthalic acid film modified glassy carbon electrode(AuNPs/poly(NDI)/GCE) has shown excellent electrocatalytic activity toward the oxidation of adrenaline(ADR),paracetamol(PAC),and tryptophan(Trp).The bare glassy carbon electrode(GCE) fails to separate the oxidation peak potentials of these molecules,while the poly(NDI) film modified electrode can resolve them.Electrochemical impedance spectroscopy(EIS)indicates that the charge transfer resistance of the bare electrode decreases as 5-[(2-hydroxynaphthalen-l-yl)diazenyl]isophthalic acid is electropolymerized on the bare electrode.Furthermore,EIS exhibits enhancement of electron transfer kinetics between analytes and the electrode after electrodeposition of Au nanoparticles.Differential pulse voltammetry results show that the electrocatalytic current increases linearly in the ranges of 0.01-680.0 μmol L~1 for ADR,0.05-498.0 μmol L~1 for PAC,and 3.0-632.0 μmol L~1 for Trp;with detection limits(S/N = 3) of 0.009 μmol L~1,0.005 μmol L~1,and 0.09 μmol L~1 for ADR,PAC,and Trp,respectively.The proposed method has been successfully applied for simultaneous determination of ADR,PAC,and Trp in biological samples.