Numerical and experimental study of turbulent impinging twin-jet flow

The two dimensional impinging circular twin-jet flow with no-cross flow is studied numerically and experimentally. The theoretical predications are carried out through numerical procedure based on finite volume method to solve the governing mass, momentum, turbulent kinetic energy and turbulent kinetic energy dissipation rate. The parameters studied were jet Reynolds number (9.5 × 10⁴  Re  22.4 × 10⁴), nozzle to plate spacing (3  h/d  12), nozzle to nozzle centerline spacing (l/d = 3, 5 and 8) and jet angle (0°  θ  20°). It is concluded that the stagnation primary point moves away in the radial main flow direction by increasing the jet angle. This shift becomes stronger by increasing the nozzle to nozzle centerline spacing (l/d). A secondary stagnation point is set up between two jets. The value of pressure at this point decreases by decreasing Reynolds number and/or increasing the jet angle.

The sub atmospheric region occurs on the impingement plate. It increases strongly by increasing Reynolds number and decreases as the jet angle and/or a nozzle to plate spacing increases. The spreading of jet decreases by increasing nozzle to plate spacing. The intensity of re-circulation zone between two jets decreases by increasing of h/d and jet angle. The increase of turbulence kinetic energy occurs within high gradient velocity.     

Reaction of 2-carboxy-1-methylindole-3-acetic acid anhydride with amines and with S-methylisothiosemicarbazide

2-Carboxy-1-alkylindole-3-acetic acid anhydrides (I) condensed with S-methylisothiosemicarbazide in DMF to form 5,11-dihydro-6-methyl-2-methylthioindolo[3′,2′:4,5]pyrido[1,2-b]-s-triazol-5-one (II). Compound II underwent ring opening on refluxing with sodium hydroxide solution to give IV. The anhydride I reacted with primary amines in benzene to give 2-carboxy-1-alkylindole-3-acetanilide derivatives (VI) which yielded l-methylindole-3-acetic acid by decarboxylation followed by hydrolysis. Compound II oxidised to the diketo compound X which could be prepared by the hydrolysis of the azomethine derivative IX with acetic acid-hydrochloric acid mixture. Compound II reacted with benzyl chloride to yield the dibenzyl derivative XII, condensed with p-chlorobenzaldehyde to form the 11-p-chlorobenzylidene derivative XI and coupled with arenediazonium salt to give the 11-arylhydrazone derivatives XIII.     

Alpha-nitro ketone synthesis using N-acylbenzotriazoles

[Reaction: see text]. Readily available N-acylbenzotriazoles 2a-l (derived from a variety of aliphatic, (hetero)aromatic, and N-protected alpha-amino carboxylic acids) smoothly convert primary 3a-c and alpha-functionalized primary nitroalkanes 3d into the corresponding alpha-nitro ketones 5a-p in yields of 39-86% (average 63%).     

Darstellung und schwingungsspektren von trimethylzinndiorganothiophosphinaten Me3SnOSPR′R″ (R′R″ = Me2, MePh,Ph2). Die kristallstruktur von Me3SnOSPMe2

A series of trimethyltin diorganothiophosphinates Me₃SnOSPR′R″ (R′R″ = Me₂, MePh, Ph₂) was prepared from (Me₃Sn)₂O and R′R″PSCl in cyclohexane solution. A close study of the vibrational spectra is given; ³¹P NMR and mass spectra are also reported. The structural investigation of Me₃SnOSPMe₂ by means of X-ray diffraction (R 5.2%, 1697 observed independent reflexions) shows the compound to consists of chains, in which planar SnMe₃ units and tetrahedral OSPMe₂ groups are linked by the O- and S-atoms of the thiophosphinate.     

Synthesis,characterization and metal chelating properties of silica-physisorbed and chemisorbed-2,5-dioxypiperazine

2,5-Dioxypiperazine (DOPZ) was covalenty bonded as a chelating compound to chloropropyltrimethoxysilane (Si–Cl) for the formation of a new chemisorbed silica [Si–(CH₂)₃–DOPZ]. Physisorbed silica-loaded-2,5-dioxypiperazine [Si–DOPZ] was also synthesized via a physical adsorption approach. Elucidation of the chemisorption and physisorption of 2,5-dioxypiperazine onto silica was confirmed on the basis of 70 eV electron impact mass spectrometric (70 eV EI-MS) mode of ionization via a direct insertion probe (DIP) as a promising technique for providing characteristic fragment ion peaks. The metal probe testing method and elemental analysis were applied to determine the surface coverage values and these were found to be 0.179 and 0.160 mmol g⁻¹ for [Si–(CH₂)₃–DOPZ] and 0.251 mmol g⁻¹ for [Si–DOPZ]. [Si–(CH₂)₃–DOPZ] was characterized by high stability in acidic and buffer solutions, pH 1–7, compared to [Si–DOPZ]. Differential scanning calorimetry studies (DSC) for the modified silica were performed to evaluate the various thermodynamic and kinetic parameters of the thermal degradation processes, and these have been enumerated. The results obtained by both EI-MS and DSC are very similar in many respects. Metal chelation and stoichiometric properties of chemically modified silica were evaluated on the basis of the metal binding capacity, distribution coefficient and separation factor for a series of metal ions. The evaluated results refer to the high metal chelating properties of [Si–(CH₂)₃–DOPZ] for cadmium(II), lead(II) copper(II) and mercury(II). These four [Si–(CH₂)₃–DOPZ]–metal complexes were also synthesized and the identified stoichiometric ratios were found to be 1:2 based on the nitrogen and metal analysis. EI-MS via 70-eV ionization was also used as a potential method for further confirmation of the metal complex formation based on structure and fragmentation elucidation. DSC studies of these four metal complexes were also performed and evaluated.     

Expedient acylations of primary and secondary alkyl cyanides to alpha-substituted beta-ketonitriles

Primary and secondary cyanides are efficiently acylated with N-acylbenzotriazoles 3a-f (derived from a variety of acids) to afford the corresponding alpha-substituted beta-ketonitriles 5a-r in 67-96% yields.     

Efficient conversion of sulfones into beta-keto sulfones by N-acylbenzotriazoles

Acyclic sulfones 4a-f and alicyclic sulfone 7 react with readily available N-acylbenzotriazoles 3a-g (derived from aliphatic, aromatic, and heteroaromatic carboxylic acids) to provide the corresponding beta-keto sulfones 5a-n and 8a-c, respectively, in good to excellent yields.     

Benzotriazole-assisted thioacylation

[Chemical reaction: See text] Benzotriazole reagents for thioacylation (RCSBt), thiocarbamoylation (RR'NCSBt), aryl/alkoxythioacylation (ROCSBt), and aryl/alkylthiothioacylation (RSCSBt) are synthesized, and their utility is assessed by syntheses of representative heteroaryl thioureas 3a-g, thioamides 15a-s, thionoesters 16a-h, thiocarbamates 17a-e, dithiocarbamates 18a-d, thiocarbonates 19a-c, and dithiocarbonates 20a-c.     

The radiation-induced degradation of a diazo dye in aqueous solution,II

The effect of -radiation on the color intensity of aerated, deaerated and oxygenated aqueous solutions of a diazo dye (Helion Red 8B) has been investigated. The decoloration yields of Helion Red 8B neutral aqueous solution, G(-Dye), for the nitrogen-, oxygen- and aerated-saturated solutions were found to be 0.77, 0.46 and 0.36 in the respective early stage. The rate constant for the reaction of the OH radical with the HR8B dye, obtained from competition kinetics using ethanol, was found to be 1.3·10¹⁰ M^–1·s^–1. In aerated solutions (pH 3), the G(-Dye) decreased markedly upon the addition of a very small amount of ethanol. Suggestions are made for possible use of the dye as a radiation dosimeter in the dose range of 0.1 to 2 kGy.