Molybdenum was separated with alkylphosphonic acid PC-88A by solvent extraction method, from the leach liquor containing copper, rhenium and iron among other impurities. The extraction efficiency of molybdenum was about 96% at pH 0.8 with zero co-extraction of other metals. The loaded organic was stripped with ammonia aqueous solution. One extraction stage and two stripping stages were required for the enrichment of Mo
The reaction mixture was then merged at a Y-piece with a reagent stream consisting of potassium ferrocyanide and luminol in alkaline solution. Detection: The elicited chemiluminescence intensity was measured by a photomultiplier tube operated at a voltage of 880 V. Range: 0.1–14 µg mL-1 8. “TLC for Neomycin Sulphate”  Stationary Phase: silica gel Mobile Phase: 3%ammonium:Acetone
Chemical Reaction of Carboxylic Acids Main Contributor: Chen Swee Lun Carboxylic acids consists of a huge and diverse group of organic compounds that contain the carboxyl group (-COOH). The general formulae for carboxylic acid is CnH2n+1COOH. The presence of hydrogen atom in the carboxyl group gives carboxylic acids an acidic property when the acid is dissolved in water. Methanoic acid, ethanoic acid and propanoic acid are some examples of carboxylic acids. Formic acid, acetic acid and propionic acid are the common names for the three examples respectively.
One noticeable exception is the so-called “Atwal modification” of the Biginelli reaction. In this scheme, an enone(a) is first condensed with a suitable protected urea or thiourea derivative(b) under almost neutral conditions. Deprotection of the resulting 1,4-dihydropyrimidine(c) with HCl or TFA leads to the desired DHPMs.20 Scheme-3: Shutalev et al described another approach to DHPMs synthesis. This synthesis is based on the condensation of readily available R-tosylated (thio)ureas(a) with the enolates of acetoacetates or 1,3-dicarbonyl compounds. The resulting hexahydropyrimidines(b) need not to be isolated and can be converted directly into DHPMs.
Since alkenes are immiscible with concentrated HBr, tetrabutylammonium bromide is used as a phase-transfer catalyst. It forms a complex with HBr and extracts it from the aqueous phase into the organic phase where the alkene is. This dehydrates the acid, making it more reactive so that the addition reaction is possible. Rapid stirring is required in order to maximize the surface area
The results show an agreement with the theoretical formulas suggested from the analytical data. Complexes 1-4 have good thermostability under 250 C. Complex 1 presents three mass loss stages. The first step in the range 323.29 to 350.37 C corresponds to the loss of the partial of thiosemicarbazone by the breakdown of NN bond. Based on the DSC curve, there is a little exothermic signal (Tp = 329.69 C, H = -214.07 Jg-1).
Potassium ferricyanide was supplied from Riedel laboratory reagents. Thiobarbituric acid, monochloroacetic acid and trichloroacetic acid were supplied from SUVCHEM laboratory chemicals. Other reagents and solvents were of analytical grade. 2.1. Preparation of CMCS The carboxymethylation process of CS into water soluble CMCS was carried out according to the method reported previously (Qian et al., 1996; Chen, et al., 2004).
The acidity of the hydrogen at C-(2) was predicted to be pKa 20 while for oxazole itself the pKb is reported to be pKb 1.17. Oxazoles exhibit distinctive resonances in both 1H NMR and 13C NMR spectra. The parent compound displays resonances between 7.00 and 8.00 in the 1H NMR spectrum, and the existence of substituents can change the chemical shift by up to 1 ppm. The 13C NMR of oxazole displays characteristic aromatic resonances. The shielding or deshielding effect of C (2) substitution on the C (4) and C (5) resonances is usually < 2 ppm.
In this stage the decomposition of monosaccharides was accompanied with the formation of gaseous brown coloring matter. The second stage consisted of the decomposition of the gaseous products from 340οC to 400οC. This phase was accompanied by several endothermic reactions which were attributed to reactions between the gaseous products. The TG analysis indicated that the pyrolysis to carbonaceous materials was practically completed at around 400oC, leaving a remaining mass percentage of 18%, which was composed of various forms of
They can impart localised structural rigidity, confer cytotoxicity by alkylation, or be secondary metabolites . The chemistry of epoxides is dominated by the reactions that involve opening of the strained three-membered heterocyclic ring by nucleophiles. Such reactions yield valuable bifunctional compounds. In nature, epoxide ring opening is catalysed by the phenolic proton of a tyrosine moiety . But in laboratory, the cleavage usually occurs in non-aqueous media in presence of a Lewis acid