Synthesis and Characterization of Silica@Copper Core–Shell Nanoparticles: Application for Conjugate Addition Reactions

Silica@copper (SiO₂@Cu) core–shell nanoparticles were synthesized and well characterized by XRD, TEM, AFM, XPS, UV/Vis, TGA–MS, and ICP–AES techniques. The synthesized SiO₂@Cu core–shell nanoparticles were employed as catalysts for the conjugate addition of amines to α,β‐unsaturated compounds in water to obtain β‐amino carbonyl compounds in excellent yields in shorter reaction times. Furthermore, the catalyst works well for hetero‐Michael addition reactions of heteroatom nucleophiles such as thiols to α,β‐unsaturated compounds. As the reaction is performed in water, it allows for easy recycling of the catalyst with consistent activity.     

57Fe Mössbauer spectroscopic study of (25−x)MnO–xZnO–15Fe2O3–60B2O3 glasses

The ⁵⁷Fe Mössbauer technique has been used to investigate the effect of zinc oxide substitution in (25???x)MnO–xZnO–15Fe₂O₃–60B₂O₃ glass system (x?=?0, 5, 10, 15 and 20 mol% of ZnO ). Mössbauer absorption spectra for all the samples recorded at room temperature suggest the existence of the two paramagnetic quadrupole doublets. The observed variations in hyperfine parameters have been explained on the basis of cations distribution and exchange interaction at the lattice sites and it is concluded that B–B interaction increases while the metal–metal interaction decreases due to replacement of manganese oxide by zinc oxide. These results suggest that the present glass system exhibits a paramagnetic behaviour that changes towards the weak paramagnetic when manganese oxide was replaced with zinc oxide.     

Photochemical C–N bond forming reactions for the synthesis of five-membered fused N-heterocycles

Abstract

Few conversions cannot take place with ground-state reactions even with the help of a catalyst, therefore they are made to occur under photochemical conditions. The transfer of electrons took place even with the photochemical excitement of one molecule where redox reaction cannot occur at the ground state. The ground-state reactions resulted in the formation of side products. The substrates did not require any sort of chemical activation for C–N bond construction in the course of photochemical reactions. The source of energy; light has always been the interest of researchers in order to induce chemical reactions ever since the starting of scientific chemistry. The present review encloses the chemistry of photochemical transformations with a focus on their synthetic uses. The organic photochemical reactions prevent the polluting or harmful reagents thus, provides a possibility for sustainable procedures as well as green chemistry. This review article displays the formation of numerous of five-membered fused nitrogen-heterocyclic compounds.     

Synthesis of some new 4-imino-3,5,7-trisubstituted-pyrido[2,3-d]pyrimidine-2(1H)-thiones

The synthesis of 4-imino-3,5,7-trisubstituted-pyrido[2,3-d]pyrimidine-2(1H)-thiones is described. The elemental analysis, ir and nmr spectral data confirm the structure of the products.     

Ag-mediated synthesis of six-membered N-heterocycles

Abstract

One of the highly emerging and an important aspect of organic chemistry is the metal catalyzed synthesis of heterocycles. The methods used earlier for the synthesis of heterocycles were significant in the organic synthesis and developing cost-effective, improved and facial methods were beneficial to construct the complex architectures. For the both stereoselective and regioselective synthesis of six-membered nitrogen containing heterocycles, cyclic reactions that are Ag-mediated have known to be very efficient. The present review covers the applications of Ag in the formation of six-membered nitrogen containing heterocycles.     

A Spectrophotometric Study of Fe(III) Chelates of Some Hydroxy Coumarin Derivatives

Chelates formation of Fe(III) with 7–hydroxy–4–methyl coumarin–6–carboxylic acid (HMCCH)₂ and 8–amino–7–hydroxy–4–methyl coumarin (AHMCH) have been studied. It has been observed that Fe(III) forms 1:2 (metal:ligand) chelates with HMCCH₂ and AHMCH. The stability constants of these chelates at different ionic strengths and the effect of temperature on the stability constants of these chelates have been studied. The thermodynamic parameters such as entropy change (ΔS), free energy of formation (ΔG) and enthalpy change (ΔH) have also been calculated. The effect of dielectric constant oh the stability constants of these chelates have been studied. Estimation of nanogram quantities of Fe(III) with these ligands and the effect of diverse ions have also been studied and the results have been compared with other methods used for estimation of Fe(III).     

Phosphorylated chitin as a chemically modified polymer for ecofriendly corrosion inhibition of copper in aqueous chloride environment

Research on Chemical Intermediates - Heterocyclic organic molecules containing oxygen, nitrogen or sulfur are generally used as inhibitors for corrosion protection of copper. These compounds form...     

Elucidating the intermolecular hydrogen bonding interaction of proline with amides—quantum chemical calculations

Structural Chemistry - The hydrogen-bonded complexes formed between proline and amides have been investigated completely by the use of computational methods such as Atoms In Molecules (AIM),...