Ultrasound assisted synthesis of some new 1,3,4-thiadiazole and bi(1,3,4-thiadiazole) derivatives incorporating pyrazolone moiety

Novel substituted 1,3,4-thiadiazole and bi(1,3,4-thiadiazole) were synthesized from reaction of 1-methyl-5-oxo-3-phenyl-2-pyrazolin-4-thiocarbox-anilide with a series of different hydrazonyl halides or N,N'-diphenyl-oxalodihydrazonoyl dichloride. The reactions were carried out under both conventional and ultrasonic irradiation conditions. In general, improvement in rates and yields were observed when reactions were carried out under sonication compared with classical condition. Structures of the products were established on analytical and spectral data.     

Diversity oriented heterocyclizations of pyruvic acids,aldehydes and 5-amino-<Emphasis Type="Italic">N</Emphasis>-aryl-1<Emphasis Type="Italic">H</Emphasis>-pyrazole-4-carboxamides: catalytic and temperature control of chemoselectivity

Heterocyclization reactions of pyruvic acids, aromatic aldehydes and 5-amino-N-aryl-1H-pyrazole-4-carboxamides yielding four different types of final compounds are described. The reactions involving arylidenpyruvic acids lead with high degree of selectivity to either 4,7-dihydropyrazolo[1,5-a]pyrimidine-5-carboxylic acids or 5-[(2-oxo-2,5-dihydrofuran-3-yl)amino]-1H-pyrazoles, depending on the catalyst type or temperature regime. The interactions based on arylpyruvic acids can take place under kinetic or thermodynamic control producing 7-hydroxy-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidine-7-carboxylic acids or 3-hydroxy-1-(1H-pyrazol-5-yl)-1,5-dihydro-2H-pyrrol-2-ones, respectively.     

Ultrasound-assisted dehydrogenation of 5-acetyl-3,4-dihydropyrimidin-2(1H)-ones

In this study, various 5-acetyl-3,4-dihydropyrimidin-2(1H)-ones were synthesized and the dehydrogenation of these compounds by potassium peroxydisulfate in aqueous acetonitrile under thermal and sono-thermal conditions were investigated. Whereas the effect of the nature of 4-substituent influences the rate of reaction, the application of sonic waves decreases drastically the time of thermal reaction.     

A comparison between the sonochemical and thermal reaction of 5H,5Cl-dibenz[a,d]cycloheptatriene with nitrobenzene

The reaction of 5H,5Cl-dibenzo[a,d]cycloheptatriene with nitrobenzene was investigated under both thermal (210 degrees C) and ultrasonic (50 degrees C, 40 kHz) activation. The reaction products of both procedures are similar, but their amounts depend on the activation source. To account for the products a common electron transfer reaction is postulated through the dibenzotropylium cation. The differences between the thermal and ultrasonic process is thought to arise from the role of nitrobenzene as oxidant. Under thermal conditions this occurs throughout the reaction mixture but under sonication it occurs only in the cavitation bubble and in its immediate vicinity.     

Development of practical methodologies for the synthesis of novel 3(4-oxo-4H-chromen-3-yl)acrylic acid hydrazides

We report a new environmentally-benign, convenient and facile methodology for the synthesis of new series of 3(4-oxo-4H-chromen-3-yl)acrylic acid hydrazides derivatives designed by exploring the molecular hybridization approach between isoniazide and 3(4-oxo-4H-chromen-3-yl)acrylic acids by using EDCl/HOBt under ultrasound irradiation in very short reaction time. Utilization of easy reaction conditions, isolation and purification makes this manipulation very interesting from an economic perspective.     

Microwave assisted IMDAF# reaction: microwave irradiation applied with success to cycloaddition reaction of N-propargyl-N-p-tolyl-N-2-furfurylamines

The new tertiary furfurylamine with triple bond as a dienophylic part i.e. N-(5-methyl-2-furfuryl)-N-prop-2-ynyl-p-toluidine (1) was prepared and the intramolecular Diels-Alder reaction of the amine (1) was performed under microwave irradiation conditions and by heating a benzene solution of the amine under nitrogen. Comparing the results of the usual thermal and the MAOS reaction, we confirmed our expectations that MAOS could promote the outcome of IMDA reaction of the suitably N-substituted tertiary 2-furfuryl-amines. In the present example, N-p-tolyl-5-methyl-5,7a-dihydro-5,7a-epoxyisoindoline was obtained in much better yield and of higher purity.     

Spectroscopic Elucidation of the Coordination Ability of 2-Oxo-2H-Chromene-3-Phosphonic Acid with Pt(II)

The coordination ability of 2-oxo-2H-chromene-3-phosphonic acid with Pt(II) both in solution and in solid state is elucidated by means of conventional and linear-polarized IR spectroscopy of oriented colloid suspensions in nematic liquid crystal, ¹H-, ¹³C-, and ³¹P-NMR, UV-Vis spectroscopy, positive and negative mass spectrometry (ESI and FAB), and TGV and DSC methods. A comparison with the spectroscopic data of ammonium salt of 2-oxo-2H-chromene-3-phosphonic acid is carried out as well.     

Kinetics and mechanism of nickel ferrite formation under high temperature ultrasonic treatment

The effect of simultaneous ultrasonic and thermal treatment on kinetics and mechanism of nickel ferrite formation was studied. It was established that sonication leads to notable increase of the mean rate of this reaction and decrease of effective activation energy from 190+/-5 to 125+/-7 kJ/mol. XRD data show that ultrasonic treatment significantly affects the microstructure of both initial reagent (Fe(2)O(3)) and reaction product (NiFe(2)O(4)) thus promoting formation of well developed reaction zone. A general model of ferrite formation mechanism under high temperature ultrasonic treatment was proposed.     

Corrosion on continuous supercritical water oxidation for polychlorinated biphenyls

Abstract

The corrosion resistance of Hastelloy C-276 and titanium alloy G5 against C1 anion which was generated by supercritical water oxidation (scWO) of 3-chlorobiphenyl (3-PCB) in a flow reactor was investigated over a period of 336 hours at a constant pressure of 30 MPa. The condition of the scWO reaction zone was fixed at 750 K. The concentration of chlorine in the effluent collected after cooling to ambient temperature was about 850 wppm. The Hastelloy C-276 has a nominal ratio of approximately 3.7 Ni/l Cr. The Ni/Cr ratio in the effluent was the same with the nominal ratio, and the Hastelloy C-276 was proved to be corroded on the surface located between the bottom of the reactor and the cooling parts, which are under sub- and near- critical conditions of water. The corrosion rate was found to be 5 to 34mm/y in the zone where the temperature ranged from 543 K to 650 K and the corrosion spread over the whole surface of the alloy; however, one can hardly observe such a serious corrosion except the zone located in the between the reactor and the cooling part.     

Synthesis and evaluation of functionalized indoles as antimycobacterial and anticancer agents

A new series of 5-fluoro-N(2)-(cyclohexylidene)-3-phenyl-1H-indole-2-carbohydrazides (6a-6e) and their cyclization products 5-fluoro-N-(3-oxo-1-thia-4-azaspiro [4.5]dec-4-yl)-3-phenyl-1H-indole-2-carboxamides (7a-7e, 8a-8e) have been synthesized and evaluated for in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv using the Microplate Alamar Blue Assay (MABA). Compounds showed moderate to good inhibitory activity at 6.25 μg/mL. Among them, 7b, 7d, 8b, and 8d were the most potent analogs with an inhibition range of 91-95?%. Additionally, compounds 6a, 7a, 7e, 8a, and 8e were subjected to the National Cancer Institute's (NCI) in vitro disease-oriented antitumor screening to be evaluated for antitumor activity. 8e, the most potent compound examined, displayed broad spectrum antiproliferative activity with particular selectivity against four leukemia cell lines (CCRF-CEM, HL-60 (TB), K-562, and RPMI-8226) with log (10) GI (50) values between -5.68 and -6.09.     

A reinvestigation of the acid-promoted heterocyclization of 2-(2-oxo-2-arylethyl)malononitriles in the presence of amines

The reinvestigation of the acid-promoted cyclization of 2-(2-oxo-2-arylethyl)malononitriles, in the presence of benzylamine or aniline, in ethanol or acetonitrile, has confirmed that this is a long-time reaction process for a low-yielding synthesis of 2-amino-5-arylfuran-3-carbonitriles (2), or 2-amino-5-aryl-1-phenyl-1H-pyrrole-3-carbonitriles (4), depending on the base used. However, the microwave-assisted synthesis of 2-amino-5-(4′-methoxyphenyl)furan-3(4)-(di)carbonitriles (2c and 3c) proceeds in shorter reaction times and higher yields than does the classical thermal heating protocol. In these reactions we have observed for the first time, and characterized by their spectroscopic data and X-ray analysis, the unexpected formation of 2-amino-5-aryl-3 (4)-(di)carbonitriles (3), whose formation has been rationalized by density functional theory (DFT) analysis of the proposed reaction mechanism.     

Ultrasound-assisted reaction of 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide with potassium salt of curcumin under PTC conditions

Reaction of 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide with potassium salt of curcumin [bis-1,7-(3'-methoxy-4'-hydroxy)phenyl-5-hydroxy-1,4,6-heptatrien-3-one] under either thermal or high pressure conditions affect the labile substrate, curcumin, thus resulting in drastic reduction in the yields of the glucosides. This drawback could be effectively overcome by carrying out the biphasic reaction in the presence of a phase transfer catalyst under the effect of ultrasound. The reaction under the sonochemical conditions was faster and resulted in the increased yield of the glucoside products. The reaction was investigated in detail with a view to optimizing the yield of the glucosides. The detailed study clearly indicated the important role of the nature and quantity of the phase transfer catalyst employed in the reaction. Also, the selectivity with respect to the formation of mono- or di-beta-glucosides under both mono- and biphasic reaction conditions was clearly discernable. The study establishes a simple synthetic protocol for the glucoside derivatives of curcumin in high yields and selectivity using ultrasonic waves.     

六氟偏磷酸锂的热分解动力

采用在线耦合TGA-FTIR技术,分别研究了非等温和等温两种条件下六氟磷酸锂(LiPF₆)的热分解动力学和其气态产物. 结果表明LiPF₆分解反应为单步反应,其产物为固态LiF和气态PF₅. 在两种条件下,LiPF₆分解动力学均遵循基于柱坐标对称的二维相界面移动模型. LiPF₆分解活化能为104 kJ/mol(非等温)和92 kJ/mol(等温).     

An efficient synthesis of 1,8-dioxo-octahydro-xanthene derivatives promoted by a room temperature ionic liquid at ambient conditions under ultrasound irradiation

The condensation reaction involving an aldehyde and diketone was efficiently promoted by the Ionic liquid, [Hbim]BF(4) (IL) as a reaction medium with methanol as co-solvent at ambient temperature under ultrasonic irradiation to afford the corresponding 1,8-dioxo-octahydro-xanthene (xanthene) derivatives in excellent yields. The advantages of this method include among others the use of a recyclable, non-volatile ionic liquid, which promotes this protocol under ambient temperature without the requirement of any added catalyst. The reaction times and yields are compared with p-TSA catalyzed synthesis of xanthenes under thermal conditions, which is also reported for the first time under our reaction conditions.     

C.I. Reactive Black 5 decolorization by combined sonolysis and ozonation

Decolorization of the azo dye C.I. Reactive Black 5 (RB5) in solution by a combination of sonolysis and ozonation was investigated. The results showed that the optimum pH for the reaction was 11.0, and both lower and higher pH decreased the decolorization rate. Increasing the initial concentration of RB5 led to a decreasing decolorization rate. Under the experimental conditions, the decolorization rate increased with an increase in temperature. The decolorization of RB5 followed pseudo-first-order reaction kinetics. Based on the decolorization rate constants obtained at different temperatures within the range 287-338K and the Arrhenius equation, the apparent activation energy (E(a)) was calculated to be 11.2kJmol(-1). This indicated that the reaction has little dependence on temperature. The color decay was considerably faster than the decrease in total organic carbon (TOC), which was attributed to the ease of chromophore destruction. Hence the efficiency of decolorization was 84% compared with 4% of TOC removal after 5min reaction. Additionally, muconic acid, (2Z)-pent-2-enedioic acid and maleic acid were identified as main oxidation products by gas chromatography coupled with mass spectrometry (GC-MS) after 150min of reaction.     

The oxidation of CO on the Pt(100)-(5 × 20) surface

The kinetics of the CO oxidation reaction were examined on the Pt(100)-(5 × 20) surface under UHV conditions. The transient isothermal rate of CO₂ production was examined both for exposure of an oxygen-dosed surface to a beam of CO and for exposure of a CO-dosed surface to a beam of O₂. Langmuir-Hinshelwood kinetics were found to apply in both cases. For the reaction of CO with preadsorbed oxygen atoms, the reaction rate was dependent upon the square-root of the oxygen atom coverage, suggesting that oxygen atoms were adsorbed in islands on this surface. The oxidation of preadsorbed CO was observed only when the initial CO concentrations were less than 0.5 monolayer (c(2 × 2) structure), suggesting that the dissociative adsorption of oxygen required adjacent four-fold surface sites. The activation energy calculated for the reaction of CO with preadsorbed oxygen was 31.4 kcal/mol. This value was 30 kcal/mol greater than the activation energy measured for the reaction of O₂ with preadsorbed CO. Strong attractive interactions within the oxygen islands were at least partially responsible for this difference. The reaction kinetics in both cases changed dramatically below 300 K; this change is believed to be due to phase separation at the lower temperature.     

Influence of various degradation conditions on the properties of gas-generating soils in the process of their decontamination

The properties of gas-generating soils (GGS) in the process of biofermentation under anaerobic and aerobic conditions are studied. The degradation of organic matter (OM) in a soil under natural occurrence conditions (without free access of air oxygen) at temperatures from 10 to 12°C is demonstrated to proceed at a specific reaction rate of k = 0.096 year^?1. The main phase of gas generation (biogas formation) is shown to take 15 years, with the content of methane in the biogas being 60?80 vol %. It has been established that, under the conditions of forced aeration of the GGS array, the specific reaction rate of OM degradation increases 10-fold, to 0.9673 year^?1, with a nearly complete decomposition of OM taking 1.5?2.0 years. A prerequisite for achieving of the predicted result is the maintenance of the environment humidity at a level not lower than 50%. Application of an alternative method, a thermal treatment of GGS increases the degree of OM decomposition to 59% within 4 h at 200°C and to 75% within 2 h at 300°C. In this case, residual organic substances are carbonized in the course of thermal treatment, transforming into a material resistant to microbiological decomposition. In fact, after heating at 200?300°C, GGS becomes inert from the gas-geochemical point of view.     

C1＋HN3产生NCl（a^1Δ）和NCl（b^1∑）的实验研究

对利用微波放电直接解离Cl2生成Cl,Cl与HN3反应生成Ncl（a^1Δ）和NCl(b^1∑）的过程进行了实验研究,得到了较强的Ncl(a^1Δ）和NCl（b^1∑）自发辐射光谱,考察了Cl2流量和He/Cl2配比对NCl(a^1Δ)和NCl(b^1∑）生成的影响,发现对于一定的He流量,Cl2流量对NCl(a^1Δ)和NCl(b^1∑）生成的影响存在一最佳范围,而最佳He/Cl2配比不是一定值,而是随He流量升高而变大,在实验所考察的He流量范围（5－40L/min)内,最佳He/Cl2配比在30：1－100：1之间。     

Comparable structural and optical properties of 4H-pyrano [3, 2-c] quinoline derivatives thin films

The structural and optical properties of 2-Amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl) - 5, 6- dihydro - 4H-pyrano [3,2-c] quinoline-3- carbonitrile (Ph-HPQ) and 2-Amino-4-(2-chlorophenyl)-6-ethyl-5-oxo-5,6-dihydro-4H-pyrano [3,2-c] quinoline-3-carbonitrile (Ch-HPQ) thin films are studied. The compounds are polycrystalline in as- synthesised powder form; they became nanocrystallites dispersed in amorphous matrix upon thermal deposition to form thin films. FTIR spectral measurements showed no change in chemical bonds of the compounds after being deposited to form thin films. The optical properties have been determined based on spectrophotometer measurements of transmittance and reflectance at nearly normal incidence of light in the spectral range of 200–2500 nm. The absorption parameters, molar extinction coefficient, oscillator strength and electric dipole strength, are reported. The type of electron transition is determined from analysis of absorption coefficient spectra near the onset and optical absorption edges. The onset and optical energy gaps for Ph-HPQ and Ch-HPQ thin films are determined. The single oscillator model is applied to calculate the dispersion parameters of the investigated thin films. In addition, oscillator and dispersion energies, the high-frequency dielectric constant, lattice dielectric constant and ratio of free charge carriers concentrations to their effective masses are evaluated for the compounds under investigation.     

Sonochemical-assisted synthesis of nano-structured lead dioxide

PbO(2) nano-powder was synthesized by the ultrasonic irradiation of an aqueous suspension of dispersed beta-PbO, as precursor, in the presence of ammonium peroxydisulfate as an oxidant. The reaction rate increased with an increase in temperature and ammonium peroxydisulfate concentration. In the presence of ammonium peroxydisulfate, the increased concentration of hydroxyl radical facilitated the oxidation of beta-PbO to PbO(2) under ultrasonic irradiation. The PbO(2) nano-powder was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the applied ultrasonic wave determines the particle size. PbO(2) samples prepared under optimized experimental conditions have lead dioxide particles in the range of 50-100 nm, as shown by SEM. The XRD results reveal that only beta-PbO(2) is formed under optimum conditions. When the reaction mixture was stirred instead of ultrasonically irradiated, only a fraction of the lead oxide was converted to lead dioxide, and lead sulfate was the main reaction product.