Elementary school students engaging in making generalisation: a glimpse from a Singapore classroom

This article reports on the generalisation strategies used by students in a grade five class in an elementary school in Singapore and the factors that seemed to influence the use of these strategies. Each student completed a novel task that required generalisation after which they were interviewed. The findings indicated that the students were using strategies that had been reported in the literature. However, this study was able to provide further understanding into factors that influence generalisation strategy use, which included: (1) the ability to see structures and relationships; (2) prior knowledge; (3) metacognitive strategies; (4) critical-thinking strategies; (5) the use of organizing heuristics such as a table; (6) the use of simplifying heuristics such as trying out simpler cases; (7) task familiarity; and (8) technology.     

A Cu protein cavity mimicking fluorescent chemosensor for selective Cu recognition: tuning of fluorescence quenching to enhancement through spatial placement of anthracene unit

Four new fluoroionophores possessing four ligating sites (2S+2N) and an essential hydrophobic environment, as prevailing in the plastocyanin and rusticyanin proteins, have been synthesized. In these PET fluoroionophores, the position of fluorophore anthracene moiety effectively modulates the Cu²⁺ induced emission properties (quenching vs enhancement) of the fluorophore. The addition of Cu²⁺ to solution of receptor with anthracene moiety in its center caused quenching in emission intensity through photoinduced fluorophore-to-metal electron transfer mechanism and in cases where anthracene is present at terminus nitrogen, the emission intensities increased by nearly 1000% due to inhibition of the photoinduced electron transfer from receptor-to-fluorophore in the presence of Cu²⁺ ions. The hydrophobic environment created by various aromatic rings clearly manifested the stability of fluorescence of these molecules above pH 2.0 and their Cu²⁺ complexes above pH 4. The application of such fluoroionophores has been elaborated for building OR and AND logic gates.     

Well-Defined Ni(0) and Ni(II) Complexes of Bicyclic (Alkyl)(Amino)Carbene (MeBICAAC): Catalytic Activity and Mechanistic Insights in Negishi Cross-Coupling Reaction

Negishi cross-coupling reaction of organozinc compounds as nucleophiles with aryl halides has drawn immense focus for C−C bond formation reactions. In comparison to the well-established library of Pd complexes, the C−C cross-coupling of this particular approach is largely primitive with nickel-complexes. Herein, we describe the syntheses of Ni(II) complexes, [(^MeBICAAC)₂NiX₂] (X=Cl ( 1 ), Br ( 2 ), and I ( 3 )) by employing the bicyclic (alkyl)(amino)carbene (^MeBICAAC) ligand. The reduction of complexes 1 – 3 using KC₈ afforded the two coordinate low valent, Ni(0) complex, [(^MeBICAAC)₂Ni(0)] ( 4 ). Complexes 1 – 4 have been characterized by spectroscopic techniques and their solid-state structures were also confirmed by X-ray crystallography. Furthermore, complexes 1 – 4 have been applied in a direct and convenient method to catalyze the Negishi cross-coupling reaction of various aryl halides with 2,6-difluorophenylzinc bromide or phenylzinc bromide as the coupling partner in the presence of 3 mol % catalyst. Comparatively, among all-pristine complexes, 1 exhibit high catalytic potential to afford value-added C−C coupled products without the use of any additive. The UV-vis studies and HRMS measurements of controlled stochiometric reactions vindicate the involvement of Ni(I)−NI(III) cycle featured with a penta-coordinated Ni(III)-aryl species as the key intermediate for 1 whereas Ni(0)/Ni(II) species are potentially involved in the catalytic cycle of 4 .     

Efficient protocol for Aza-Michael addition of N-heterocycles to α,β-unsaturated compound using [Ch]OH and [n-butyl urotropinium]OH as basic ionic liquids in aqueous/solvent free conditions

The present work emphasizes on a green methodology using designed and synthesized basic ionic liquid, [n-butyl Urotropinium]OH, and commercially available aqueous solution of choline hydroxide [Ch]OH as catalysts for executing Aza-Michael addition of N-heterocycles to α,β-unsaturated compounds at room temperature. The highlighting features of these catalysts include using low concentration of both catalysts along with [Ch]OH being low cost and biodegradable, [n-butyl Urotropinium]OH significantly enhancing the high substrate/catalyst ratio to obtain the desired products in high yield and purity in most cases. Further, both catalysts were recyclable and recoverable up to five cycles.     

Palladium acetate assisted synthesis of five-membered N-polyheterocycles

Abstract

The metal-assisted synthesis of heterocyclic compounds is known to be one of the extremely developing as well as significant concepts of organic chemistry. Because of their expensive, complex working of the instrument and difficult procedures, the methodologies used earlier for the heterocycle synthesis were less amicable to the researchers. The Pd(OAc)₂-mediated cyclic reactions have been recognized to be very effective for both the stereoselective as well as regioselective formation of the 5-membered N-bearing heterocyclic compounds. The different uses of palladium acetate, as a catalyst in the formation of 5-membered N-containing polyheterocycles, are covered in this review article.     

Performance Analysis of Nitride-Based Tunnel-Injection Transistor Laser

Journal of Russian Laser Research - Ternary alloy InGaN made of III-V nitrides has attracted significant attention from many researchers in recent years due to its tunable energy band gap from far...     

Synthesis,Molecular Docking,and Antitubercular Evaluation of Triazole–Chalcone Conjugates

Russian Journal of Organic Chemistry - The condensation of propargylated vanillin with differently substituted acetophenones produced the corresponding chalcones which were reacted with substituted...     

Graphene oxide: A carbocatalyst for the one-pot multicomponent synthesis of highly functionalized tetrahydropyridines

A simple, straightforward and efficient methodology is described for the synthesis of polysubstituted tetrahydropyridine via one-pot multicomponent reaction of β-ketoester, aldehyde and aniline in presence of catalytic amount of graphene oxide in acetonitrile. Graphene oxide is a versatile carbocatalyst and this is the first report on its application in a five component reaction. Good yield, usage of readily available starting material, operational simplicity, easy work-up and eco-friendly re-usable catalyst are the key features of this protocol.     

Trimethylsilyl bis(Fluorosulfonyl)imide : An Efficient Catalyst for the Addition of Trimethylsilyl Cyanide to Carbonyl Compounds

In the presence of 1 mol% of trimethylsilyl bis(fluorosulfonyl)imide, trimethylsilyl cyanide adds efficiently to carbonyl compounds. The catalyst has been found to be more active than trimethylsilyl triflate for the above reaction.