Removal by additives

The butane-containing streams in petroleum refineries come from a variety of different process units consequently, varying amounts of butanes in mixtures containing other light alkanes and alkenes are obtained. The most common recovery techniques for these streams are lean oil absorption and fractionation. A typical scheme involves feeding the light hydrocarbon stream to an absorber-stripper where methane is separated from the other hydrocarbons. The heavier fraction is then debutanized, depropanized, and de-ethanized by distillation to produce C, C, and C2 streams, respectively. Most often the stream contains butylenes and other unsaturates which must be removed by additional separation techniques if pure butanes are desired. 

The fluorination of P-diketones and p-ketoesters with N-/luorobis(trifluo-romethanesulfonyl)imide (Table 3a, B) can be controlled to give either mono-fluorination or difluorination. Monofluorination occurs when the strong acid, bis(trifluoromethanesulfonyl)imide, a reaction product, is removed by addition of water, which prevents further enolization and fluormation of the monofluoro adduct [83] (equation 38)... 

Shono et al. (1979) describe a method for hydro-de-diazoniations which is simple, gives excellent yields, and is claimed to show no unfavorable substituent effects (14 examples). It consists of the addition of thiophenol (7 equiv.) to a suspension of an arenediazonium tetrafluoroborate in a mixture of water and pentane (10 1) at room temperature. After the completion of N2 evolution, excess thiophenol is removed by addition of Na2C03. The usual work-up gave the corresponding hydrocarbon in 84-100% yield and diphenylsulfide. The deuterated compounds are obtained if one uses C6H5SD and D20. 

Since the ketene will copolymerize with cyclopropanone, excess ketene was removed by addition of 3A molecular sieves followed by evacuation at 1 mm Hg for 2-3 hours at -70°C. The amount of ketene was monitored by FTIR analysis. Ketene has a distinct strong absorption between 2130 and 2150 cm-1 (5,6). The solution FTIR spectrum of cyclopropanone in Figure 1 was taken before ketene removal. 

Bromine is added dropwise with stirring to a solution of 100 g. (0.35 mole) of oleic acid of at least 95% purity (Note 1) in 400 ml. of dry ether maintained at 0-5°, until the color of bromine persists. About 53 g. (0.33 mole) of bromine is needed the excess is removed by addition of a few drops of oleic acid. 

Immunoradiometric assays (IRMAs) are like RIAs in that a radiolabeled substance is used in an antibody-antigen reaction, except that the radioactive label is attached to the antibody instead of the hormone. Furthermore, excess of antibody, rather than limited quantity, is present in the assay. All the unknown antigen becomes bound in an IRMA rather than just a portion, as in a RIA IRMAs are more sensitive. In the one-site assay, the excess antibody that is not bound to the sample is removed by addition of a precipitating binder. In a two-site assay, a molecule with at least two antibody-binding sites is adsorbed onto a solid phase, to which one of the antibodies is attached. After binding to this antibody is completed, a second antibody labeled with 125I is added to the assay. This antibody reacts with the second antibody-binding site to form a sandwich, composed of antibody-hormone-labeled antibody. The amount of hormone present is proportional to the amount of radioactivity measured in the assay. 

In a similar procedure [32] the sediment is wet oxidised with dilute sulphuric acid and nitric acids in an apparatus in which the vapour from the digestion is condensed into a reservoir from which it can be collected or returned to the digestion flask as required. The combined oxidised residue and condensate are diluted until the acid concentration is IN and nitrate is removed by addition of hydroxylammonium chloride with boiling. Fat is removed from the cooled solution with carbon tetrachlodithizone in carbon tetrachloride. The extract is shaken with 0.1M hydrochloric acid and sodium nitrite solution and, after treatment of the separated aqueous layer with hydroxylammonium chloride a solution of urea and then EDTA solution are added to prevent subsequent extraction of copper. The liquid is then extracted with a 0.01% solution of dithizone in carbon tetrachloride and mercury estimated in the extract spectrophotometrically at 485nm. 

As a rather strongly hydrophilic anion, nitrate requires an ISE membrane containing a strongly hydrophobic cation, as described on p. 169. This function was fulfilled in the first nitrate electrode from Orion Research by cation V [180] in nitro-p-cymene 5. The electrode can be used in the pH range 4-7. In other commercial electrodes, the ion-exchanger ion is a tetra-alkylammonium salt, for example in the electrode from Coming Co., substance XIII in solvent 6 [27]. An ISE with a renewable membrane surface was found to be very useful (see section 4.1 and fig. 4.4), in which the ion-exchanger solution contains the nitrate of crystal violet VII dissolved in nitrobenzene [191]. The NOj ISE also responds to nitrites that can be removed by addition of aminosulphonic acid. 

The methyl group was introduced by a two-step procedure. Thus, the hydrazone Michael adducts 52 were converted into the enol pivaloates 53 in excellent yields and diastereomeric excesses de > 96%) by treatment with pivaloyl chloride and triethylamine. After treatment with lithium dimethylcuprate the chiral auxiliary was removed by addition of 6n HCl in order to obtain the 5-substituted 2-methylcyclopentene carboxylate 54 in good yields and with excellent stereoselectivity (de, ee > 96%). Finally, the asymmetric synthesis of dehydroiridodiol (55, R = Me, = H) and its analogues was accomplished by reduction of 54 with lithium aluminum hydride or L-selectride leading to the desired products in excellent yields, diastereo- and enantiomeric excesses (de, ee > 96%). 

The sulphate process consists in kiering pieces of wood in a solution composed of sodium hydroxide, sodium sulphide and sodium carbonate in a 65 15 20 ratio. The concentration of the solution is 10-12% of NaOH. Boiling at a temperature of 170-175°C under pressure lasts about 6 hr, of which 3 hr are required for heating, the other 3 hr being the kiering proper. Cellulose is then separated from the lye, washed with water, bleached, and subjected to final purification. The lye is condensed, evaporated to dryness, then sodium sulphate is added, and the whole is calcined. The sodium sulphate is thus reduced to sodium sulphide. Unchanged sulphate and the excess of carbonate are removed by addition of milk of lime. 

To HEPES buffer (100 mL, 200 mM, pH 7.5) were added ManNAc 15 (1.44 g, 6 mmol), PEP sodium salt (1.88 g, 8 mmol), pyruvic acid sodium salt (1.32 g, 12 mmol), CMP (0.64 g, 2 mmol), ATP (11 mg, 0.02 mmol), pyruvate kinase (300 U), myokinase (750 U), inorganic pyrophosphatase (3 U), /V-acctylneuraminic acid aldolase (100 U), and CMP-sialic acid synthetase (1.6 U). The reaction mixture was stirred at room temperature for 2 days under argon, until CMP was consumed. The reaction mixture was concentrated by lyophilization and directly applied to a Bio-Gel P-2 column (200-400 mesh, 3 x 90 cm), and eluted with water at a flow rate of 9 mL/h at 4°C. The CMP-NeuAc fractions were pooled, applied to Dowex-1 (formate form), and eluted with an ammonium bicarbonate gradient (0.1-0.5 M). The CMP-NeuAc fractions free of the nucleotides were pooled and lyophilized. Excess ammonium bicarbonate was removed by addition of Dowex 50W-X8 (H+ form) to the stirred solution of the residual powder until pH 7.5. The resin was filtered off and the filtrate was lyophilized to yield the ammonium salt of CMP-NeuAc 17 (1.28 g, 88%). 

Reagent. Sulphanilic acid (0 5 gram) and a-naphthylamine (o-i gram) are each dissolved in 150 c.c. of 30% acetic acid and the solutions then mixed. The vessels in which the solutions are prepared should previously be washed with acetic acid. In some cases the mixture exhibits a faint red coloration, which is removed by addition of zinc dust also after long standing this coloration may appear, but it is prevented by the presence of zinc dust. 

Weakly nucleophilic heterocyclic amines have efficiently been acylated utilizing solid-supported reagent 7 [13]. Here, the electron-deficient phenol group allows for intermediate anchoring of an acyl chloride onto the resin which then is released upon treatment with various 2-aminopyridines and 2-aminothiazoles. Traces of unreacted starting material were then conveniently removed by addition of the acidic ion exchange resin Amberlite IRA-120. 

The lyophilized samples from RP-HPLC contain TFA salts of the peptide. Although this is not a problem between RP-HPLC steps, it could be important the final pure product. The TFA will exchange slowly in buffered solutions but may interfere with some methods, such as crystallization. TFA salts and residual solvents can be removed by addition of 0.01M sodium hydroxide, and then exchanging the protein on a Sephadex G-25 column equilibrated with water and lyophilizing. 

A weighed amount of lignin is acetylated overnight at room temperature with a mixture of purified pyridine-acetic anhydride (1 1, v/v). Excess acetic anhydride is decomposed by the addition of methanol-ice water. After evaporation of the mixture to dryness, the residue is suspended in toluene and again evaporated (repeated three times). In this process, the remaining traces of acetylation mixture are removed by azeotropic distillation. Subsequently, the toluene can be removed by addition of methanol and evaporation. This method allows complete recovery of the sample with a minimum of added impurities. 

The doublet at 318.34/318.40 nm can be resolved from the adjacent 318.54 nm line with a 0.03 nm spectral bandpass. As all three lines have similar absorption sensitivity, transmission of the three lines using a 0.2nm spectral bandpass is recommended for increased detectivity and precision. Optimum sensitivity is obtained with a slightly fuel-rich nitrous oxide-acetylene flame ionization should be suppressed with 1000 jug K ml-1. Variable enhancement of absorption by Al, Fe, Cr and other elements is removed by addition of 2000 jug Alml-1. 

B) Hexabromostearic Acid.—In a 4-1. beaker equipped with a mechanical stirrer (Note 1), 90 to 95 g. of the fatty acids is dissolved in 2.5 1. of ethyl ether, and the solution is chilled to 0-10°. Then, with stirring, 35 cc. of bromine (Notes 2 and 3) is introduced slowly, from a dropping funnel (Note 4), at such a rate that the temperature does not exceed 20° about fifty minutes is usually required. The solution, which must contain an excess of bromine (deep red color), is allowed to stand in an ice bath at 0-10° overnight. The excess bromine is removed by addition of a small amount of amylene, and then the white precipitate is collected with suction on a 12.5-cm. Buchner funnel and is washed with 200 cc. of ethyl ether. The hexabromide is... 

Octene was mixed with the dirhenium heptoxide catalyst (0.1 mol % to 2 mol % based of olefin), cooled, and the oxidizing solution (in the reagent ratio range of 1 2 to 1 14 olefin/peroxide) added. After the reaction was complete, the reaction was filtered, cooled, unreacted peroxide removed by addition of sodium sulfite, and desiccant added to remove water. The product was isolated by vacuum distillation. 

Esterification of amino acids. The amino group of an amino acid can be protected as the enamine 1, formed by reaction with ethyl acetoacetate and a base in benzene/ DMSO. After alkylation the protective group is removed by addition of an acid, particularly TsOH, to provide amino acid ester salts (equation I). 

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