Separation of urea,hexamethylenetetramine, and their reaction products in sol–gel feed solution by zwitterionic HILIC

Studies were carried out to develop a chromatographic methodology based on hydrophilic interaction liquid chromatography (HILIC) for the separation of various reaction products of hexamethylenetetramine (HMTA) –urea used in the sol–gel process for the preparation of ceramic microspheres. Different chromatographic parameters such as organic modifiers, pH of mobile phase, buffer concentration, column temperature, etc. were studied to arrive at the optimum conditions for separation. Compounds such as urea, monomethylolurea (MMU), dimethylolurea (DMU), and HMTA were separated from a synthetic mixture using a mobile phase consisting of acetonitrile and acetate buffer of pH 6. The methodology developed based on HILIC stationary phase is simple and amicable for integration with electrospray ionization mass spectrometry (ESI-MS) to identify the unknown reaction products. The methodology was applied for the separation of reaction products in pre-boiled and untreated urea–HMTA mixtures used as feed in the sol–gel process.     

Sulfamic acid-catalyzed multicomponent synthesis of 7-phenyl-7,12 dihydrobenzo(h)pyrido[2,3-b]naphthydrin-6(5H)-one derivatives: a green avenue

Research on Chemical Intermediates - A series of novel 7-phenyl-7,12-dihydrobenzo(h)pyrido[2,3-b]naphthydrin-6(5H)-one were synthesized by a one-pot three-component condensation of...     

Matrix Assisted and/or Laser Desorption Ionization Quadrupole Ion Trap Time-of-Flight Mass Spectrometry of WO<Subscript>3</Subscript> Clusters Formation in Gas Phase. Nanodiamonds,Fullerene, and Graphene Oxide Matrices

The formation of W _x O _y ^+●/-● clusters in the gas phase was studied by laser desorption ionization (LDI) and matrix assisted laser desorption ionization (MALDI) of solid WO₃. LDI produced (WO₃) _n ^{+ ●/- ●} (n = 1-7) clusters. In MALDI, when using nano-diamonds (NDs), graphene oxide (GO), or fullerene (C₆₀) matrices, higher mass clusters were generated. In addition to (WO₃) _n ^-● clusters, oxygen-rich or -deficient species were found in both LDI and MALDI (with the total number of clusters exceeding one hundred ≈ 137). This is the first time that such matrices have been used for the generation of(WO₃) _n ^+●/-● clusters in the gas phase, while new high mass clusters (WO₃) _n ^-● (n = 12-19) were also detected.

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Friedländer condensation of 5‐aminopyrazole‐4‐carbaldehydes with reactive α‐methylene ketones: Synthesis of pyrazolo[3,4‐b]pyridines

A series of 1,3,6‐trisubstituted and 1,3,5,6‐tetrasubstituted pyrazolo[3,4‐b]pyridines 5 has been synthesized by Friedlander condensation of 5‐arninopyrazole‐4‐carbaldehydes 3 with α‐methylene ketones such as acetone (4a) or acetophenones 4b‐f with potassium hydroxide as basic catalyst. Condensation of 5‐aminopyrazole‐4‐carbaldehydes 3 and unsymmetric dialkylketones 6 yielded mixtures of isomeric pyra‐zolo[3,4‐b]pyridine derivatives 7 and 8 . Condensation of 5‐aminopyrazole‐4‐carbaldehydes 3 with CH‐acidic acylacetonitriles 9 and acylacetates 11 with piperidine as basic catalyst yielded pyrazolo[3,4‐b]pyri‐dine‐5‐carbonitriles 10 and pyrazolo[3,4‐b]pyridine‐5‐carboxylates 12 ; with diethyl malonate 13 as CH‐acidic component, pyrazolo[3,4‐b]pyridin‐6‐ones 14 were obtained.     

Synthesis of Novel Spiro-Oxazino-Quinoline Derivatives and Study of Their Photophysical Properties

A convenient route was successfully developed for the synthesis of novel heterocycles such as spiro-oxazino-quinoline derivatives from 2-aminoquinoline-3-carbonitrile (4) in good yield. The Spiro-quinoline derivatives (6, 8 and 10) were synthesized and further studied for their photophysical properties. Semiempirical molecular orbital calculation (PM3/PM6 for structure) proves to be a suitable tool for the prediction of absorption and fluorescence properties of these compounds.     

Multiresidue analysis of 83 pesticides and 12 dioxin-like polychlorinated biphenyls in wine by gas chromatography–time-of-flight mass spectrometry

A multiresidue method is described for simultaneous estimation of 83 pesticides and 12 dioxin-like polychlorinated biphenyls (PCBs) in red and white wines. The samples (20 mL wine, acidified with 20 mL 1% HCl) were extracted with 10 mL ethyl acetate (+20 g sodium sulphate) and cleaned by dispersive solid-phase extraction (DSPE) with anhydrous calcium chloride and Florisil successively. The final extract (5 mL) was solvent exchanged to 1 mL of cyclohexane:ethyl acetate (9:1), further cleaned by DSPE with 25 mg primary secondary amine sorbent and analyzed by gas chromatography–time-of-flight mass spectrometry (GC–TOF-MS) within 31 min run time. The limits of quantification of most analytes were ≤10–20 μg/L. Acidification of wine prior to extraction prevented hydrolysis of organophosphorous pesticides as well as dicofol, whereas treatment with CaCl₂ minimized the fatty acid co-extractives significantly. Solvent exchange to cyclohexane:ethyl acetate (9:1) further minimized the co-extractives. Recoveries at 5, 10 and 20 ng/mL were >80% for most analytes except cyprodinil, buprofezin and iprodione. The expanded uncertainties at 10 ng/mL were <20% for most analytes. Intra-laboratory precision in terms of Horwitz ratio of all the analytes was below 0.5, suggesting ruggedness of the method. Effectively, the method detection limit for most analytes was as low as up to 1 ng/mL in both red and white wine, except for cyfluthrin and cypermethrin.     

Polymer‐Supported Sulfonic Acid‐Catalyzed Candid Synthesis and Photophysical Properties of 2H‐indazolo[2,1‐b]phthalazinetriones

Polystyrene‐supported sulfonic acid has been found to be an efficient catalyst for the one‐pot, three‐component synthesis of 2H‐indazolo[2,1‐b]phthalazinetriones in greener solvent glycerol. Use of greener solvent glycerol along with a polymer‐supported, low toxic, and inexpensive catalyst renders the method eco‐friendly. High yields, simple product isolation procedure, and fluorescent and electroluminescent natures of the products are the noteworthy aspects of this protocol.     

The electronic structure of Si/GaP(110) interface and superlattice

It is argued that the (110) interface between group IV and III–V semiconductors are more likely to lend themselves to fabrication via MBE techniques. Results for the electronic structure of Si-GaP(110) superlattice are reported for the first time. Both, interface states and two dimensionally confined states are found. Sensitivity of the energy and charge distribution of these states to the interfacial geometry and the band edge discontinuity is investigated. The results are contrasted with the situation found for lattice matched III–V compound semiconductor systems such as GaAs/AlAs and GaSb/InAs.