Adsorption of HOOO. radical on pristine and doped graphene—a first-principles study

Structural Chemistry - It is believed that HOOO. radicals play a key role in atmospheric and environmental chemistry as well as in biological oxidation reactions. In the present contribution, we...     

Estimation of indoor radon, thoron and their progeny using twin cup dosemeters with solid-state nuclear track detectors in Digboi of Upper Assam

The seasonal variations of indoor radon, thoron and their progeny levels were studied in 20 houses situated in the oil-rich areas of Digboi of Upper Assam. Solid-state nuclear track detectors LR-115 type II were exposed using plastic twin chamber dosemeters to record tracks formed by the two gases and their progeny. Inhalation doses were found out using extracted equilibrium factors and ventilation rates. The random (counting) errors in track densities were determined.     

Stereodynamics of Metal–Ligand Assembly: What Lies Beneath the “Simple” Spectral Signatures of C2‐Symmetric Chiral Chelates

A series of C₂‐symmetric chiral tetra‐dentate ligands were prepared by using [4,5]‐ or [5,6]‐pinene‐fused 2,2′‐bipyridyl units that are supported across a rigid arylene–ethynylene backbone. These conformationally pre‐organised chelates support stable 1:1 metal complexes, which were fully characterised by UV/Vis, fluorescence, circular dichroism (CD), and ¹H NMR spectroscopy. A careful inspection of the exciton‐coupled circular dichroism (ECCD) and ¹H NMR spectra of the reaction mixture in solution, however, revealed the evolution and decay of intermediate species en route to the final 1:1 metal–ligand adduct. Consistent with this model, mass spectrometric analysis revealed the presence of multiple metal complexes in solution at high ligand‐to‐metal ratios, which were essentially unobservable by UV/Vis or fluorescence spectroscopic techniques. Comparative studies with a bi‐dentate model system have fully established the functional role of the π‐conjugated ligand skeleton that dramatically enhances the thermodynamic stability of the 1:1 complex. In addition to serving as a useful spectroscopic handle to understand the otherwise “invisible” solution dynamics of this metal–ligand assembly process, temperature‐dependent changes in the proton resonances associated with the chiral ligands allowed us to determine the activation barrier (ΔG^≠) for the chirality switching between the thermodynamically stable but kinetically labile (P)‐ and (M)‐stereoisomers.     

Nano-Mgo-Catalyzed One-Pot Synthesis of Phosphonate Ester Functionalized 2-Amino-3-Cyano-4H-Chromene Scaffolds at Room Temperature

Abstract

A facile and efficient protocol for one-pot three-component synthesis of structurally diverse (2-amino-3-cyano-4H-chromen-4-yl)phosphonic acid diethyl esters from the reaction of salicylaldehydes, malononitrile (or ethyl cyanoacetate), and triethylphosphite using basic nanocrystalline MgO as catalyst in aqueous ethanolic medium at room temperature has been developed. Nano-MgO has been prepared using a simple sol-gel approach. Clean reaction profile, easy reusability of MgO nano-catalyst, mild reaction condition, good yields, and practical applicability are the major advantages of the present protocol.     

A very simple and highly efficient procedure for N-formylation of primary and secondary amines at room temperature under solvent-free conditions

N-Formylation of primary and secondary amines has efficiently been carried out at room temperature in excellent yields by using catalytic amount of sodium formate in formic acid under solvent-free conditions. The process is remarkably simple and environmentally benign.     

Selection of Suitable Combination of Nonfunctional Micellar Catalyst and Heteroaromatic Nitrogen Base as Promoter for Chromic Acid Oxidation of Ethanol to Acetaldehyde in Aqueous Medium at Room Temperature

The effect of the promoter and micellar catalyst on chromic acid on the oxidation of ethanol in aqueous acid media has been studied. Picolinic acid (PA), 1,10‐phenanthroline (phen), and 2,2′‐bipyridine (bipy) are used as promoters. Sodium dodecyl sulfate (SDS), cetyl pyridinium chloride (CPC), and Triton‐X‐100 (TX‐100) are tested as micellar catalysts. Hexavelent chromium is an active species in the absence of the promoter. In the presence of the heteroaromatic nitrogen bases used as the promoter, Cr(VI)–PA, Cr(VI)–bipy, and Cr(VI)–phen complexes have been proposed as the active oxidants. The time taken for completion of the reaction using different combinations of promoter and micellar catalysts are different. Although the rate is highest (12.5 times) in TX‐100 in the absence of the promoter, it is observed that the rate is almost 737 times faster for the combination of SDS and bipy compared to the unpromoted and uncatalyzed path. CPC inhibits the oxidation process. The observed acceleration and retardation of the rate of oxidation process has been explained on the basis of partitioning of the reactants in the micellar and aqueous phase. © 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: 175–186, 2013     

On domination and independent domination numbers of a graph

For a graph G, the definitions of domination number, denoted γ(G), and independent domination number, denoted i(G), are given, and the following results are obtained:Theorem.If G does not have an induced subgraph isomorphic to K_1,3, thenγ(G) = i(G).Corollary 1.For any graph G, γ(L(G))=i(L(G)), where L(G) is the line graph of G. (This extends the result γ(L(T))=i(L(T)), where T is a tree. Hedetniemi and Mitchell, S. E. Conf. Baton Rouge, 1977.)Corollary 2.For any Graph G, γ(M(G))=i(M(G)), where M is the middle graph of G.     

Global dynamics of the advanced light source revealed through experimental frequency map analysis

Frequency map analysis was first used for the dynamical study of numerical simulations of physical systems (solar system, galaxies, particle accelerators). Here it is applied directly to the experimental results obtained at the Advanced Light Source. For the first time, the network of coupling resonances is clearly visible in an experiment, in a similar way as in the numerical simulation. Excellent agreement between numerical and experimental results leads us to propose this technique as a tool for improving numerical models and actual behavior of particle accelerators. Moreover, it provides a model-independent diagnostic for the evaluation of the dynamical properties of the beam.     

On the equality of the grundy and ochromatic numbers of a graph

It is proved in this note that the Grundy number, Γ(G), and the ochromatic number, χ⁰(G), are the same for any graph G.