Quinoxaline Research Papers - Academia.edu (original) (raw)

The most cytotoxic compound from a library of quinoxaline-containing peptides is endocyted into HeLa cells, accumulates in acidic compartments, and blocks autophagy by altering lysosomal function, leading to apoptosis activation.

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- Chemistry, Oncology, Nuclear Magnetic Resonance, Biology
- by Elena Petricci
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- Materials Science, Microwave, Medicine, Microwave Irradiation

Among the environmental factors that may contribute to the genesis of human cancer, diet is regarded as a major determinant. It was of interest therefore to study the human exposure to heterocyclic aromatic amines found in various meat products. This study aims at a qualitative analysis of food carcinogens employing the Electrospray Ionization Mass Spectrometry. A total of three samples namely Peppered Mackerel, Chicken Salami and Bacon Grill randomly collected from the local grocery stores of New Delhi, India were analyzed for the presence of food carcinogens. Standard carcinogenic compounds namely PhIP (2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine ) and MeIQx (2-amino-3,8 dimethylimidazo[4,5-f] quinoxaline) were employed as reference mutagens. Results obtained establish the presence of a potential hallmark carcinogen MeIQx whose mass corresponds to (m/z = 214.09) in Bacon Grill, concluding the detection of MeIQx. We were unable to detect either of the indicated mutagens in Peppered Mackerel and Chicken Salami respectively.

- by VIJAY KUMAR PRASAD
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- Chemistry, Food Science, Cancer, food Nutrition
- by VIJAY KUMAR PRASAD
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- Chemistry, Biology, Cytotoxicity, DNA damage
- by VIJAY KUMAR PRASAD
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- Chemistry, Food Science, Chromatography, Mass Spectrometry
- by Hemant Chavan
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- Chemistry, Organic Chemistry, CHEMICAL SCIENCES, Polyethylene Glycol
- by Hemant Chavan
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- Chemistry, Organic Chemistry, Polyethylene Glycol, Quinoxaline

Spherical silver nanoparticles (NP-Ag) stabilized in shells of poly(N-vinylpyrrolidone) (PVP) are synthesized electrochemically by the benzimidazo[1',2':1,2]quinolino [4,3-b][1,2,5]oxodiazolo [3,4-f]quinoxaline (BIQOQ)-mediated reduction of Ag + ions in the presence of PVP and cellulose nanofibers (NC) at the potential controlled at the BIQOQ -generation in the DMF/0.1 M Bu 4 NBF 4 medium at room temperature. The mediator is not consumed in this process, the generated metal is not deposited on the cathode, being formed in solution volume in the quantitative yield corresponding to the theoretical quantity of electricity passed. The synthesized products represent cellulose nanofibers decorated most compactly with silver nanoparticles covered by PVP shells Ag@PVP/NC. The size of NP-Ag in Ag@PVP/NC (11 ± 3 nm) is much lower as compared with the Ag@PVP nanocomposite synthesized by the methyl-viologen-mediated reduction of Ag + ions under similar conditions in the absence of NC (20 ± 7 nm). The synthesized nanocomposite exhibits catalytic activity in the reactions of reduction of nitroaromatic compounds by sodium borohydride in aqueous media.

- by Vitaly Yanilkin
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- Chemistry, Electrochemistry, Nanoparticle, Metal

In the present study, a new 'turn on' fluorescent sensor, (E/Z)-enaminone containing a pyrrolo [2,3-b]quinoxaline group as the fluorophore and a N,N-bis(pyridin-2ylmethyl)ethylenediamine group as a specific chelator capable of selective detection of Zn 2+ is reported. The structure of the ligand was determined by IR, MS, and 1D and 2D NMR, including 1 H-15 N HMBC correlations. X-ray analysis for (E/Z)-2 confirmed the presence of 90.3% E-diastereoisomer and 9.7% Z-one in the structure of the crystals obtained from acetonitrile. The mechanism of zinc ion recognition is related to the restriction of E/Z-isomerisation of enaminone occurring upon Zn 2+ binding that alters the electronic structure of the ligand. Sensing of Zn 2+ was confirmed in detail using UV-vis, fluorescent, and 1 H NMR titrations, which allowed us to propose the binding mode for complexes formed in the solution during the zinc ion recognition. The ligand functions under physiological conditions and retains its activity in buffer solutions over a wide pH range 2.4-10.6. The developed sensor allowed for intracellular sensing of Zn 2+ in human (fibroblast) and fungal (Candida albicans) cells through fluorescence imaging studies.

- by Miriam González
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- Engineering, Chemistry, Fluorescence, Biological Sciences

New approaches have been tested for the synthesis of lumateperone intermediates. As a result of these efforts, a novel synthesis of the late-stage tetracyclic key intermediate of lumateperone starting from the commercially available quinoxaline is described. The tetracyclic skeleton was constructed by the reaction of 1-trifluoroacetyl-4-aminoquinoxaline with ethyl 4-oxopiperidine-1-carboxylate in a Fischer indole synthesis. The inexpensive starting material, the efficient synthetic steps, and the avoidance of the boranebased reduction step provide a reasonable potential for scalability.

- by Balazs Volk
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- Chemistry, Organic Chemistry, Combinatorial Chemistry, Borane

Biologically active quinoxalines were efficiently synthesized in excellent yields and in less reaction time using inexpensive, monodispersed and easily recyclable Ni-nanoparticles. In order to elucidate the role of the Ni-nanoparticles, a control reaction was conducted using glyoxal and o-phenylenediamine in acetonitrile in the absence of Ni-nanoparticles. Quinoxaline was formed in around 10 h with a 30% yield. However, the same reaction carried out in acetonitrile using 10 mol% of Ni-nanoparticles (14-18 nm) at 25 °C and stirred under N 2 gave quinoxaline in quantitative yield in 10 min. The separation of the product was facile and the catalyst could be separated and recycled by mild centrifugation. Our method is very quick, avoids the use of expensive reagents, high temperatures (our reaction takes place at room temperature) and leads to excellent yield.

- by Ajeet Kumar
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- Chemical Engineering, Chemistry, Catalysis, Nanoparticle
- by Consuelo Guerri
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- Chemistry, Food Science, Pepper, Capsaicin

A series of ten chalcone-substituted quinoxalines (4a-e), (3a-e) starting from 1-(phenylquinoxalin-2-yl)ethanone and 1-(3-methylquinoxalin-2-yl)ethanone have been synthesized using conventional heating and ultrasound-assisted methods. Furthermore, novel of five quinoxaline derivatives including pyrazoline, isoxazole, pyrimidin-2-one, N-acylpyrazoline and pyridin-2-one moieties were also prepared from the reaction of chalcone compound 4a with different cyclization reagents using the same strategy. The structures of all synthesized compounds were established on the basis of FT-IR, 1H-NMR and 13C-NMR. The ultrasonic irradiation method provide several advantages over conventional heating method, including shorter reaction times (30-90 min.) and good percentage yields (65% - 88%), comparing with conventional protocol (5 to 20 hrs. with 30% to 55% reaction yields).

- by Hamid hashim
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- Chemistry, Chalcone, Green Reagent, Quinoxaline

Neglected diseases represent a major health problem. It is estimated that one third of the world population is infected with tuberculosis (TB). Besides TB, Chagas disease, affects approximately 20 million people. Quinoxalines display great activities against TB and Chagas. Forty new quinoxaline 1,4-diN oxide derivatives have been prepared and tested against M. tuberculosis and T. cruzi. Carboxylic acid quinoxaline 1,4-diN oxides (CAQDOs) 5 and 17 showed MIC values on the same order as the reference antituberculosis drug, rifampicin. Meanwhile, CAQDOs 12 and 22 presented IC 50 values in the same order as the anti-chagasic drug, nifurtimox.

- by Diego Benítez
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- Organic Chemistry, Biology, Magnetic Resonance Spectroscopy, Medicine

The synthesis, characterization, and electropolymerization of a series of extended fused-ring thieno[3,4-b]pyrazine-based terthienyls are reported. The target terthienyls contain a central extended thieno[3,4-b]pyrazine analogue containing 2-thienyl units at the reactive α-positions of the central thiophene. The extended fused-ring thieno[3,4-b]pyrazine analogues studied include acenaphtho[1,2-b]thieno[3,4-e]pyrazine, dibenzo[f,h]thieno[3,4-b]quinoxaline, and thieno[3 1 ,4 1 :5,6]-pyrazino[2,3-f ][1,10]phenanthroline. Comparison of the electrochemical and photophysical properties to simple thieno[3,4-b]pyrazine-based terthienyls and their polymeric analogues are reported in order to provide structure-function relationships within this series of compounds and materials.

- by Ryan Schwiderski
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- Engineering, Materials Science, Materials, Medicine
- by Ryan Schwiderski
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- Chemistry, Inorganic Chemistry, Organic Chemistry, Medicine

A series of bis(triazolothiadiazines) and bis(quinoxalines) were synthesized and tested for their cytotoxicity and apoptosis-induction through PARP-1 and EGFR as molecular targets. Compound 8i exhibited high cytotoxic activity and... more

- by fatma thabet
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- Chemistry, Cytotoxicity, Olaparib, Ic
- by Zhifeng Lü
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- Chemistry, Medicinal Chemistry, Hydrogen Bond, CHEMICAL SCIENCES

A novel porous organic polymer (denoted by Q-POP) was successfully fabricated by free-radical copolymerization of allyl-substituted 2,3-di(2-hydroxyphenyl)1,2-dihydroquinoxaline, and divinylbenzene under solvothermal conditions and used as a new platform for immobilization of copper nanoparticles. The CuNPs@Q-POP nanocatalyst was prepared via incorporating of Cu(NO 3) 2 into the polymeric network, followed by the reduction of Cu 2+ ion with hydrazine hydrate. The obtained materials were characterized through FT-IR, XRD, N 2 adsorption-desorption isotherms, ICP, TGA, SEM, HR-TEM, EDX, and the single-crystal X-ray crystallography. The results displayed that Q-POP and CuNPs@Q-POP possessed high surface area, hierarchical porosity, and excellent thermal and chemical stability. The assynthesized catalyst was utilized for the Ullmann C-N coupling reaction of aromatic amines and different aryl halides to prepare various diarylamine derivatives. All types of aryl halides (except aryl fluorides) were screened in the Ullmann C-N coupling reaction with aromatic amines to produce diaryl amines in good to excellent yields (50-98%), and it turned out that aryl iodides have the best results. Besides, due to the strong interactions between CuNPs, N, and O-atoms of quinoxaline moiety existing in the polymeric framework, the copper leaching from the support was not observed. Furthermore, the catalyst was recycled and reused for five consecutive runs without significant activity loss.

- by Hadi Rudbari
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- Chemistry, Catalysis, Nanoparticle, Medicine

Materials and physical techniques Reagents and solvents were purchased from Merck Company and used without further purification. Melting points were measured on an Electrothermal 9100 apparatus. IR spectra were recorded using PerkinElmer 597 and Nicolet 510P spectrophotometers as a KBr Abstract Assembly of quinoxaline with Cd(II) in the presence of SCN − anion produces a new coordination polymer [Cd(Quinoxaline)(SCN) 2 (CH 3 CN)] n [Cd(Quinoxalin e) 2 (SCN) 2 ] n (1) and is characterized by IR, 1 H NMR and 13 C NMR spectroscopy. The single-crystal X-ray data of compound 1 show that this coordination polymer grows in two-dimensional supramolecular structure. In this polymer, the organic ligand chelate through its one nitrogen atom to cadmium(II) atom and thiocyanate anion acts as a bridge to two cadmium(II) atom in the chains. Also, nanoscale of CdS has been synthesized by calcination at 400, 500 and 600 °C under air atmosphere and characterized by scanning electron microscopy, X-ray powder diffraction and energydispersive X-ray. The thermal stability of compound 1 was studied by thermal gravimetric and differential thermal analyses.

- by Hadi Rudbari
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- Chemical Engineering, Chemistry, Crystallography, Supramolecular Chemistry
- by Alan Boobis
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- Biochemistry, Chemistry, Quinoline, Ames Test

The ability of three model carcinogens, 1,2-dimethylhydrazine, dimethylnitrosamine, and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, to induce mutation in a novel in vivo assay in mouse intestine has been examined. The assay is based on mutations at the Dlb-1 locus which determines the tissue specific pattern of expressio of the binding site for the lectin Dolichos biflorus agglutinin. In C57BL/6J x SWR F1 mice Dlb-1 mutants are recognized as clones of epithelial cells not staining with a peroxidase conjugate of D. biflorus agglutinin. Chronic administration of 1,2-dimethylhydrazine (20 mg/kg/week s.c. for 10 weeks) induced Dlb-1 mutants, whereas administration of a single dose did not. Similarly, chronic dimethylnitrosamine treatment p.o. (0.001% in drinking water for 8 weeks) induced Dlb-1 mutants, but acute administration did not. In contrast, neither chronic nor acute treatment of the mice with 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline induced Dlb-1 mutations. The activiti...

- by Alan Boobis
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- Chemistry, Cancer, Medicine, Peroxidase

During the cooking of beef, the genotoxic heterocyclic aromatic amines 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) are formed. Little is known about the fate of these compounds in humans or the factors affecting it. We have developed assays based on capillary column gas chromatography-negative ion mass spectrometry capable of the simultaneous measurement of MeIQx, DiMeIQx, and PhIP in cooked meat and in human urine using stable isotope labeled analogues. Ten normal, healthy male volunteers were invited to consume a standard cooked meat meal (400-450 g lean beef, cooked as patties on a griddle hotplate) on four separate occasions over a period of 14 months. Following consumption of the test meals, urine was collected from 0 to 8 h, during which time all free amines were excreted and analyzed for MeIQx, DiMeIQx, and PhIP. Subjects ingested 240 +/- 9 (SEM) g...

- by Alan Boobis
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- Chemistry, Individuality, Cancer, Medicine

A facile and efficient method was investigated for the synthesis of different quinoxalines by the reaction of o-phenylene diamine and 2-bromoacetophenones. This procedure was carried out in ethanol under catalyst-free conditions. Several sulfonamides were synthesized from 2-(4-methoxyphenyl)-quinoxaline in two steps. At first chlorosulfonation of 2-(4-methoxyphenyl) quinoxaline was done using chlorosulfonic acid and led to 2-methoxy-5-quinoxalin-2-yl-benzenesulfonyl chloride. Then quinoxaline sulfonamides were synthesized by the reaction of quinoxaline sulfonyl chloride with different aromatic amines under solvent-free conditions. All the products were obtained in excellent yields after an easy work-up and were evaluated for antibacterial activities against Staphylococcus spp. and Escherichia coli bacteria.

- by Ahmad Reza Massah
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- Chemistry, Catalysis, Sulfonamide, Chloride
- by Azila Idris
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- Chemistry, Fluorescence
- by Azila Idris
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- Chemistry, Fluorescence
- by Paola Hernandez
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- Chemistry, Organic Chemistry, Medicinal Chemistry, Leishmania
- by Won Jo
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- Materials Science, Band Gap, Quinoxaline, Polymer Solar Cell
- by emin saripinar
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- Chemistry, Organic Chemistry, Medicinal Chemistry, Heterocyclic chemistry

A broad series of quinoxalinone-based -conjugated donor-acceptor fluoro-and NLO-phores is characterized by means of Raman spectroscopy and single-crystal X-ray analysis supported by quantum chemical computations. Intense Raman spectroscopic markers allowing to discern even closely related structures are identified. The intensities of these bands are shown to be related to the conjugation of the different molecular moieties, and they can provide an estimation of its extent. The intensity redistribution between these markers serves as a source of auxiliary structural information capable to point to a distortion of the conjugation or to the influence of aggregation effects in the condensed state. A simple relation between the intensity of the marker and the position and oscillator strength of the lowest-energy electronic absorption band of quinoxalinones allows to link the Raman effect with the optical properties of these compounds, which can be used for rational design of novel species with improved optical characteristics.

- by Sergey Katsyuba
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- Chemistry, Spectroscopy, Raman Spectroscopy, Medicine

Four chromophores belonging to a new class of push-pull chromophores with divinylphenylquinoxaline moieties have been designed and synthesized. The structure-property relationship was systematically investigated; the effect of the... more

- by Sergey Katsyuba
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- Chemical Engineering, Chemistry, Quinoxaline, Plant Dyes and Pigments

Quinoxaline derivatives are an important class of heterocycle compounds, where N replaces some carbon atoms in the ring of naphthalene. Its molecular formula is C 8 H 6 N 2 , formed by the fusion of two aromatic rings, benzene and pyrazine. It is rare in natural state, but their synthesis is easy to perform. In this review the State of the Art will be presented, which includes a summary of the progress made over the past years in the knowledge of the structure and mechanism of the quinoxaline and quinoxaline derivatives, associated medical and biomedical value as well as industrial value. Modifying quinoxaline structure it is possible to obtain a wide variety of biomedical applications, namely antimicrobial activities and chronic and metabolic diseases treatment.

- by Natália Cordeiro
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- Chemistry, Organic Chemistry, Drug Discovery, Medicine
- by Alexei Buevich
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- Pharmacology, Genetics, Chemistry, Organic Chemistry
- by Mercedes González
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- Chemistry, Organic Chemistry, Cytotoxicity, Medicine
- by SAYAN SAHA
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- Chemical Engineering, Chemistry, Inorganic Chemistry, Photochemistry
- by Akira Odani
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- Chemistry, Nitrogen, Quinoline, Chemical Shift
- by David Akinpelu
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- Biochemistry, Genetics, Microbiology, Chemistry

Understanding the chemical structures of next‐generation small molecules is a critical step for increasing the performance of organic photovoltaics (OPVs); an OPV's small molecule determines not only the extent of light absorption but also the morphology. Herein, four small molecules featuring different cores—indaceno dithiophene, dithienoindeno indaceno dithiophene (IDTT), substituted IDTT, and dithienothiophene‐pyrrolobenzothiadiazole—denoted as ID‐4Cl, IT‐4Cl, m‐ITIC‐OR‐4Cl, and Y7, respectively, are selected to form active layers with poly(quinoxaline) (PTQ10) and poly(benzodithiophene‐4,8‐dione) (PM6). The Y7 devices exhibit the best performance in both systems, with the power conversion efficiency (PCE) reaching 14.5%; in comparison, ID‐4Cl device gives a PCE of 10.0% for blending with PTQ10 and a relative efficiency enhancement of 45%. The same trend occurs for the cases of PM6 blend devices. This enhancement is attributed to i) the improved short‐circuit current density ...

- by Kung-hwa Wei
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- Materials Science, Photovoltaics, Small Molecule, Organic Solar Cell

New synthetic routes to trifluoromethylated N‐heterocycles based on condensations of 2‐methoxy‐2‐methyl‐5‐(trifluoromethyl)furan‐3(2H)‐one with bifunctional N‐nucleophiles are described. For the first time, trifluoromethyl‐containing pyrazoles, pyrazolines and isoxazolines bearing hydrazone or oxime groups could be obtained by a one‐pot strategy based on reactions of 5‐(trifluoromethyl)furan‐3(2H)‐one with two equivalents of the corresponding hydrazines or hydroxylamine in the presence of an acid. The interaction of furan‐3(2H)‐one with ureas proceeded under mild conditions to furnish 1H‐furo[2,3‐d]imidazol‐2(3H)‐one derivatives in good yield. Further, a trifluoromethyl‐containing quinoxaline derivative was obtained by condensation of furan‐3(2H)‐one with ortho‐phenylenediamine.

- by Yulia Kudyakova
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- Chemistry, Organic Chemistry, Quinoxaline, Hydroxylamine

The availability of affordable organic compounds with thermally activated delayed fluorescence (TADF) properties represents a unique class of materials for addressing key challenges in organic electronics. In this context, we have successfully designed and synthesised three novel hybrid molecules 2-(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)-3,7,8-triphenylpyrazino[2,3g]quinoxaline (tCz-PyrQx), 4-(tert-butyl)-N-(4-(tert-butyl)phenyl)-N-(4-(3,7,8triphenylpyrazino[2,3-g]quinoxalin-2-yl)phenyl)aniline (tDPA-PyrQx), and 2-(4-(9,9dimethylacridin-10(9H)-yl)phenyl)-3,7,8-triphenylpyrazino[2,3-g]quinoxaline (Ac-PyrQx) comprising electron-donating 3,6-di-tert-butyl-9H-carbazole, bis(4-(tert-butyl)phenyl)amine, and (9,9-dimethyl-9,10-dihydroacridine) with electron-accepting pyrazinoquinoxaline groups. The incorporation of highly planar and rigid pyrazinoquinoxaline electron-accepting moieties holds significant importance due to their unique properties like efficient charge transfer, and reduced steric hindrance. Their planar structure facilitates strong π-π stacking interactions and efficient charge transfer within the molecular framework, leading to improved exciton formation and enhanced reverse intersystem crossing (RISC) rates, which are critical for TADF processes. The three different electron-donating groups with pyrazinoquinoxaline were synthesised with the view of tuning the photophysical and electrochemical properties of the hybrids.

- by Sunil Madagyal
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- Paleontology, Physics, Materials Science, Nuclear Physics

An efficient, simple, and green procedure for the synthesis of quinoxaline derivatives is described. The condensation of 1,2-diamines with 1,2-diketones using lithium bromide (LiBr) in H 2 O/EtOH as a green reaction media at room... more

- by Mohammad Reza Mohammadizadeh
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- Chemistry, Catalysis, Quinoxaline

Quinoxalines are heterocyclic compounds that contain a benzene ring and a pyrazine ring. The oxidation of both nitrogen of the pyrazine ring results in quinoxaline derivatives (QdNO), which exhibit a variety of biological properties, including antiparasitic activity. However, its activity against Entamoeba histolytica, the protozoan that causes human amebiasis, is poorly understood. Recently, our group reported that various QdNOs produce morphological changes in E. histolytica trophozoites, increase reactive oxygen species, and inhibit thioredoxin reductase activity. Notably, T-001 and T-017 derivatives were among the QdNOs with the best activity. In order to contribute to the characterization of the antiamebic effect of QdNOs, in this work we analyzed the proteomic profile of E. histolytica trophozoites treated with the QdNOs T-001 and T-017, and the results were correlated with functional assays. A total number of 163 deregulated proteins were found in trophozoites treated with T-001, and 131 in those treated with T-017. A set of 21 overexpressed and 24 under-expressed proteins was identified, which were mainly related to cytoskeleton and intracellular traffic, nucleic acid transcription, translation and binding, and redox homeostasis. Furthermore, T-001 and T-017 modified the virulence of trophozoites, since they altered their erythrophagocytosis, migration, adhesion and cytolytic capacity. Our results show that in addition to alter reactive oxygen species, and thioredoxin reductase activity, T-001 and T-017 affect essential functions related to the actin cytoskeleton, which eventually affects E. histolytica virulence and survival.

- by Laurence Marchat
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- Biology, Virulence, Thioredoxin, Entamoeba histolytica

Deep cavitands having three fixed walls and one mobile wall were prepared. The longer wall, built from a quinoxaline spacer, showed enhanced NMR spectra of guests, but the shorter wall based on a benzene spacer showed tighter binding and slower exchange of guests. Deep cavitands are receptors that more or less surround their targets but feature one open end. They form host/guest complexes by folding around their targets and temporarily isolating them from the bulk solvent. When properly derivatized, the cavitands present functional groups to guests 1 and impose interactions otherwise found only at the active sites of enzymes. 2 This arrangement of groups on host and guest can result in large rate accelerations, 3, 4 organocatalysis 5, 6 and even the stabilization of otherwise labile reaction intermediates. 7,8 Access to greater volumes of space requires the incorporation of larger aromatic panels in the synthesis and we report here our experiences with a quinoxaline "wall". Cavitands are inevitably obtained from resorcinarenes using the synthesis devised by Högberg. The octol 1 (Fig. 1) was condensed with three equivalents of the benzene panels as previously described, 9 reduced, then acylated to give the hexamide 2-a molecule with recognition properties of its own. 10, 11 Condensation with the 2,3-dichloro-6,7-dinitroquinoxaline gave the target dinitro compound 3 in 65%. Because of two intramolecular hydrogen bonds between amides on neighboring panels, the vase-like structure is stablized as reported by the characteristic downfield shifts of the methine jrebek@scripps.edu. Supporting Information Available: synthesis of cavitand 3 and 1 H NMR spectra of binding experiments of cavitand 3 and 4 with different guests.

- by Dariush Ajami
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- Chemistry, Medicine, CHEMICAL SCIENCES, Benzene
- by Morais Morais
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- Chemistry, Quinoxaline, Pyrazine

Two studies are presented relating to a set of instructional suggestions for teaching chemical equilibrium. In the first study, we used techniques from the field of cognitive science to answer the question; "Do experts invoke Majority/Minority (M&M) reasoning during equilibrium problem solving?" To determine whether and how experts reason differently from students as they solve problems, we asked experts (chemistry professors and advanced graduate students) and novices (college undergraduates) to think aloud as they solved equilibrium problems. Analysis of this data revealed that experts were more likely than novices to invoke progress of reaction type reasoning and to demonstrate planning though using an approximation strategy. Results from this study also suggest that the M&M strategy is aligned with expert reasoning and problem solving strategies. In the second study, we compared students' exam data in two different semesters using a quasi-experimental design to evaluate whether the M&M strategy was learnable and whether instruction using the strategy improved equilibrium problem solving. Our results demonstrate that the M&M strategy is aligned with expert reasoning and problem-solving, is learnable by students and promotes problem solving performance.

- by David Klahr
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- Political Science

- by Gildardo Rivera
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- Biology, Virulence, Thioredoxin, Entamoeba histolytica

The interaction of two surfactant cobalt(III) complexes, cis-[Co(ip)2(DA)2](ClO4)31 and cis-[Co(dpq)2(DA)2](ClO4)32 where ip=imidazo[4,5-f][1,10]phenanthroline and dpq=dipyrido[3,2-d:2'-3'-f]quinoxaline with yeast tRNA have been explored by using electronic absorption, competitive binding, electrochemical studies and viscosity measurements. The results suggest that these complexes can bind to tRNA by intercalation. The presence of hydrophobic diimine ligand and the long aliphatic double chains of these complexes facilitate its intercalative interaction with the hydrophobic interior of the tRNA. The extent of tRNA binding of complex 2 has greater affinity than that of complex containing imidazo[4,5-f][1,10]phenanthroline ligands.

- by Karuppiah Nagaraj
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- Chemistry, Analytical Chemistry, Medicine, Intercalation Chemistry

Inclusion of the long aliphatic chain of the surfactant complex ion into β-cyclodextrin leads to decrease in the rate constant. Kinetic data and activation parameters are interpreted in terms of an outer-sphere electron-transfer mechanism. All these results have been interpreted in terms of the hydrophobic effect and the reactants with the opposite charge.

- by Karuppiah Nagaraj
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- Chemistry, Chemical Kinetics, Micelle, Electron Transfer

In the title compound, C35H29N3O, the quinoxaline and indene systems are essentially planar, with maximum deviations of 0.047 (2) and 0.032 (2) Å for C atoms, respectively. The quinoxaline system forms a dihedral angle of 4.75 (3)° with the indene system. The pyrrolizine system is folded. The substituted five-membered ring adopts an envelope conformation. In the other five-membered ring, one C atom is disordered with a site-occupancy ratio of 0.676 (12):0.324 (12). In the crystal, molecules are linkedviaC—H...O hydrogen bonds involving the bifurcated carbonyl O atom.

- by devadasan velmurugan
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- Chemistry, Medicine, Hydrogen Bond, CHEMICAL SCIENCES