Showing papers on "Reagent published in 1979"
TL;DR: Pyridinium poly(hydrogen fluoride) (30% pyridine-70% hydrogen fluoride) reagent, a stabilized, less-volatile form of hydrogen fluoride, was found to be a convenient and effective fluorinating agent as mentioned in this paper.
Abstract: Pyridinium poly(hydrogen fluoride) (30% pyridine-70% hydrogen fluoride) reagent, a stabilized, less-volatile form of hydrogen fluoride, was found to be a convenient and effective fluorinating agent. Fluorination, halofluorination, nitrofluorination, and hydrofluorination of olefins were achieved using the reagent. The in situ diazotization and subsequent fluorinative dediazonization of a-amino acids, aminoarenes, and carbamates yielded a-fluorocarboxylic acids, aryl fluorides, and fluoroformates, respectively. Geminal dihalides and a-halo ketones were reacted with mercuric oxide in pyridinium poly(hydrogen fluoride) to form geminal difluorides and a-fluoro ketones. Solutions of alkali halides in pyridinium poly(hydrogen fluoride) were also found to be effective halogenating agents for aminoarenes, via in situ diazotization and subsequent nucleophilic dediazonization by the corresponding halides, as well as for alcohols, via SN2 type displacement reactions. Diazo ketones and diazoalkanes also reacted smoothly with halide ions in pyridinium poly(hydrogen fluoride) solution to give the corresponding geminally halofluorinated compounds.
418 citations
TL;DR: The retention mechanism of reversed-phase "ion-pair" liquid chromatography was investigated in this paper, and it was shown that ion-pair formation does not occur in the mobile phase and the capacity of solute ions is increased by mobile phases containing ion-interaction reagents of the opposite charge over the range 0 to 20 mM.
353 citations
TL;DR: In this paper, a mixture of chlorotrimethylsilane/sodium iodide in acetonitrile is found to be a better reagent than iodotrim methylsilane for the cleavage of esters, lactones, carbamates, and ethers.
Abstract: A new, convenient, inexpensive alternative to iodotrimethylsilane reagent is explored. A mixture of chlorotrimethylsilane/sodium iodide in acetonitrile is found to be a better reagent than iodotrimethylsilane for the cleavage of esters, lactones, carbamates, and ethers. Cleavage of esters and lactones (10 examples) occurred somewhat slower with the present system than with iodotrimethylsilane. On the other hand, ethers (7 examples) cleaved much more readily with the present system. A feasible mechanism is proposed for this disparity. Carbamates (6 examples) also underwent facile cleavage to give the corresponding amines. The general applicability of the method has been shown using various types of substrates. The facile conversion of alcohols to iodides using the present method is also reported. Ccinversion of alcohols to iodides is much faster with chlorotrimethylsilane/sodium iodide than with iodotrimethylsilane, and iodides are formed in excellent yield.
331 citations
TL;DR: It was found that the pH of the sodium phosphotungstate-magnesium precipitation method was a critical factor in the method and the distribution of high-density lipoprotein cholesterol in a healthy adult population was skewed to the left for women and bi-modal for men.
Abstract: When determining high-density lipoprotein cholesterol by use of sodium phosphotungstate-magnesium precipitation method, I found that the pH of the sodium phosphotungstate reagent was a critical factor in the method. Unless the pH of the reagent was less than 7.6, the precipitation of low-density lipoprotein and very-low-density lipoprotein was incomplete. When the specimen pH was between 7.35 and 8.65, the pH of the serum of plasma did not influence the completeness of precipitation. Optimum concentrations of precipitation reagents, determined after the pH of the sodium phosphotungstate reagent was standardized to pH 6. 15, were 40 g/L for sodium phosphotungstate and 2 mol/L for MgCl2. The distribution of high-density lipoprotein cholesterol in a healthy adult population was skewed to the left for women (n = 34; mean = 660 mg/L) and bi-modal for men (n = 44; mean = 460 mg/mL). The central 95% reference interval was 280 to 880 mg/L for women and 250 to 750 mg/L for men.
274 citations
Patent•
15 Oct 1979TL;DR: In this paper, an improved heterogenous specific binding assay method which employs a substance having reactant activity, i.e., a reactant, as a labeling substance in the detection of a ligand in a liquid medium was proposed.
Abstract: An improved heterogenous specific binding assay method which employs a substance having reactant activity, i.e., a reactant, as a labeling substance in the detection of a ligand in a liquid medium. The method is carried out using reagent means which comprises, as its labeled constituent, a conjugate formed of a specific binding substance coupled to the reactant. The reactant advantageously is an enzymatic reactant such as an enzyme substrate or coenzyme. The activity of the conjugated reactant as a constituent of a predetermined reaction system is utilized as means for monitoring the extent of binding of the labeled constituent in conventional heterogenous specific binding assay schemes. The presence of a ligand in a liquid medium may be determined following conventional competitive binding manipulative techniques. After the necessary separation of the bound-and free-phases resulting in the specific binding reaction system, the extent of binding of the labeled constituent is determined by contacting either phase with the necessary materials to form the predetermined monitoring reaction system in which the labeling substance is active and assessing reactant activity therein.
241 citations
238 citations
TL;DR: In this paper, a method for the rapid determination of phospholipid phosphorus in samples containing less than 0.5 μg phosphorus is described, which is first converted to inorganic phosphate by heating a dried lipid extract briefly over a Bunsen flame in the presence of magnesium nitrate, then dissolving the resulting residue in dilute hydrochloric acid at 95 C.
Abstract: A method is described for the rapid determination of phospholipid phosphorus in samples containing less than 0.5 μg phosphorus. Phospholipid phosphorus is first converted to inorganic phosphate by heating a dried lipid extract briefly over a Bunsen flame in the presence of magnesium nitrate, then dissolving the resulting residue in dilute hydrochloric acid at 95 C. The determination of the inorganic phosphate content of the sample then requires only the addition of Triton X-100 and an acidic ammonium molybdate-malachite green reagent. Absorbance is measured at 650 nm after 5 min at room temperature.
231 citations
213 citations
TL;DR: In this paper, a double proportional injector is described, and an improvement of the continuous flow-injection method is discussed, where sample and reagent are both injected into an inert carrier stream; the reagent is consumed only in the presence of the sample, and can otherwise be recovered continuously.
187 citations
TL;DR: In this paper, an efficient conversion of primary and secondary hydroxy-groups into iodo-groups, with inversion, in carbohydrates was described using either triphenylphosphine, iodine, and imidazole in toluene at elevated temperature.
Abstract: Efficient conversions of primary and secondary hydroxy-groups into iodo-groups, with inversion, in carbohydrates are described using either triphenylphosphine, iodine, and imidazole or triphenylphosphine and 2,4,5-tri-iodoimidazole in toluene at elevated temperature.
169 citations
TL;DR: The fluorescence properties of the products formed by reaction of o-phthaldialdehyde with amino acids and their derivatives, in the presence of thiol compounds, have been studied and the report that the product incorporates molecules of all three types of compounds is confirmed.
TL;DR: The procedure employed was exactly as previously described as discussed by the authors, and all cases the alcohols isolated were identical with the known compounds by TLC, which are included here for those compounds where they are not in the literature.
Abstract: General Procedure for the Ozonolysis-Reduction of 8,9,11, 13, and 16. The procedure employed was exactly as previously described.13 In all cases the alcohols isolated were identical with the known compounds by TLC. 'H NMR, and 13C NMR data, which are included here for those compounds where they are not in the literature. 1:3 6a: 13C NMR (CDC13) 6 24.42, 24.97, 25.99, 26.07 (4CH3), 62.16 (Cs), 68.38, 70.71, 70.85, 71.56 (Cz-Cj), 96.36 (Ci ) , 108.70, 109.50 (2C(CH3)z).
TL;DR: The reaction products of F-propene and dialkylamines, mixtures of α,α-difluoroalkylamine and α-fluoro enamine, were found to be useful fluorinating agents for alcohols and carboxylic acids as mentioned in this paper.
Abstract: The reaction products of F-propene and dialkylamines, mixtures of α,α-difluoroalkylamine and α-fluoro enamine, were found to be useful fluorinating agents for alcohols and carboxylic acids. These reagents were superior to the adduct of chlorotrifluoroethene and diethylamine, the so-called Yarovenko reagent, for their readier preparation and higher stability.
TL;DR: A simple modification of the Dittmer-Lester reagent is described that allow the detection of phospholipid derivatives at very low concentrations on silica gel and reversed-phase thin-layer plates.
TL;DR: Aqueous hydrofluoric acid is an excellent reagent for the removal of t -butyldimethylsilyl protecting groups as discussed by the authors, but it is not suitable for the extraction of polycyclic acid.
TL;DR: In this paper, the reduction of methionine sulfoxide in peptides and proteins has been systematically investigated in terms of specific reducing agent, concentration of reducing agents, temperature, pH of the solution, and presence of denaturing agents.
Patent•
12 Feb 1979
TL;DR: An aqueous reagent system for quantita-tive determination of protein is described in this article, which contains Coomassie Brilliant Blue G-250 dye, a monobasic strong acid having a pKa of less than 3, a polybasic phosphonic acid (e.g. NTP), and a water soluble, nonionic surfactant characterized as being a block copolymer containing terminal polyethylene oxide segments separated by a polypropylene oxide segment.
Abstract: An aqueous reagent system for the quantita-tive determination of protein is disclosed. The sys-tem contains Coomassie Brilliant Blue G-250 dye, a monobasic strong acid having a pKa of less than 3 (e.g. HC1), a polybasic phosphonic acid (e.g. NTP), and a water soluble, nonionic surfactant characterized as being a block copolymer containing terminal polyethylene oxide segments separated by a polypropylene oxide segment. Preferably the sys-tem also contains a small amount of an alcohol such as methanol or ethanol.
TL;DR: In this paper, primary α-acetylenic alcohols undergo regio-and stereo-specific additiions of Grignard reagents in the presence of cuprous halides.
TL;DR: A turbidimetric procedure for the determination of ammonia in low concentrations with the use of Nessler's reagent is described in this article, where both natural waters and soil extracts can be analyzed at a rate of up to 120 samples per hour with good precision and accuracy.
Abstract: A turbidimetric procedure for the determination of ammonia in low concentrations with the use of Nessler's reagent is described. Both natural waters and soil extracts can be analysed at a rate of up to 120 samples per hour with good precision and accuracy. The effects of reagent composition, flow-rate, temperature and protective colloids in the flow injection system are discussed in detail.
TL;DR: A new bifunctional reagent for the cross-linking and reversible immobilization of proteins through their amine groups that reacts rapidly with proteins, at pH 7 and at high dilution, appears suitable for studies involving proteins with essential disulfide linkages.
TL;DR: Arylation of BrZnCH2CO2CH2CH3 by aromatic halides proceeds smoothly and in fair yield in a mixture of dimethoxymethane and a dipolar aprotic solvent (HMPA, NMR (N-methylpyrrolidone), DMF, DMSO) when catalysed by soluble nickel or palladium complexes.
TL;DR: Alkaline hydrolysis of peptides is carried out prior to detection to increase the sensitivity of the method and is convenient for the manual determination of 5 to 100 nmol of amino acids in the 50–100 samples required to define a chromatographic elution profile.
TL;DR: In this paper, a modified Strecker synthesis was proposed for the synthesis of α-amino nitriles from carbonyl compounds and amines, which is called a modified Stecker synthesis.
TL;DR: Carbonsauren (II) werden with Cyanurchlorid (I) uber diskutierte Zwischenstufen in die Saurechloride (III) ubergefuhrt, die mit Alkoholen, Phenolen, Aminen oor auch Aminosauren direkt zu Estern, Amiden oder Peptiden (IV) umgesetzt werding as mentioned in this paper.
TL;DR: In this article, it was shown that a layer of solvent exists over the surface of the bonded phase which can be shown by the nature of the adsorption isotherm of methanol on the bond phase; this was also confirmed chromatographically.
TL;DR: In this article, photoacoustic spectroscopy was used to determine the surface coverage of high surface area (400 m/sup 2/g) silica by reaction of the silica with alkane solutions of (1,1'-ferrocenediyl)dichlorosilane (Ia), ( 1,1]-dimethyl-dimethylsilane, (Ib), or (1.1]-diphenyl-silane(Ic).
Abstract: Ferrocene-centered reagents can be bound to the surface of high surface area (400 m/sup 2//g) silica by reaction of the silica with alkane solutions of (1,1'-ferrocenediyl)dichlorosilane (Ia), (1,1'-ferrocenediyl)dimethylsilane (Ib), or (1,1'-ferrocenediyl)diphenylsilane (Ic). Derivatization is not found when ferrocene itself is used as the derivatization reagent; ferrocene is easily washed from the silica powder by solvents which do not affect the ferrocene centers bound upon reaction of the silica with Ia-c. As determined by photoacoustic spectroscopy, derivatization with Ia-c results in ring opening of the strained C-Si-C linkage bridging the two cyclopentadienyl rings to yield a simple, monosubstituted ferrocene center attached to the surface. Surface -OH functionality apparently reacts in a manner analogous to homogeneous solution sources of -OH such as MeOH. Reaction of Ib with MeOD yields (Fe(eta/sup 5/-C/sub 5/H/sub 4/D)(eta/sup 5/-C/sub 5/H/sub 4/Si(OMe)Me/sub 2/)). Optical absorption spectral changes accompanying reaction of Ia-c with solution sources of -OH are consistent with the differences found in the photoacoustic spectra of the pure powders of Ia-c compared to the silica powders derivatized with these reagents. Reaction of silica powders derivatized with Ia-c with acidic solutions of benzoquinone results in the oxidation of the surface-confined ferrocene centers to ferricenium centers giving photoacoustic spectramore » nearly the same as that from an authentic sample of a pure ferricenium salt. The surface-confined ferricenium can be used to oxidize N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) to TMPD/sup +/. in solution; this reaction allows an estimate of the surface coverage at 10/sup -11/ mol/cm/sup 2/. 3 figures, 2 tables.« less
TL;DR: The maximum absorbance of the complex is proportional to initial polymer concentration over the range 0-100 mg dm-3 for PVA polymers with degrees of hydrolysis in the range 75-100 mole-%, in the presence of an excess of boric acid, iodine and potassium iodide as mentioned in this paper.
TL;DR: In this paper, the formation of secondary N-nitrosoamines when MeCN solutions of amines are brought into contact with gaseous NO, N2O3, and n2O4 at 25 °C is reported.
Abstract: The formation of secondary N-nitrosoamines when MeCN solutions of amines are brought into contact with gaseous NO, N2O3, and N2O4 at 25 °C is reported. With NO, N-nitrosoamine formation from piperidine, morpholine, and diphenylamine occurs very slowly (t½ca. 8 days). Reaction rates are largely independent of the amine, suggesting that oxidation of NO by adventitious oxygen is the slow step. Very much faster reactions are observed, however, with N2O3 and N2O4. With a ca. 10-fold excess of N2O3 or N2O4, quantitative yields of both N-nitrosopiperidine and N-nitrosodiphenylamine are found in less than 3 min. With a 27-fold excess of piperidine and N2O4 only, ca. 8%N-nitropiperidine and 92%N-nitrosopiperidine are obtained. Rapid reactions also ensue when solutions of either primary aromatic or secondary amines dissolved in 0.1M-aqueous NaOH are brought into contact with gaseous N2O3 and N2O4. With a ca. 2–400-fold excess of these nitrogen oxides, 12–65% of the amine is converted either to N-nitrosoamine or diazonium ion in less than 3 min. Competitive hydrolysis of the nitrogen oxide by the solvent is not HO–-catalysed and the amine : H2O reactivities are in ca. 1 000 : 1. The extent of N-nitrosation varies insignificantly over a wide range of basicities (pKa, 11.12 to –1.0), but no reaction occurs with either 2,4-dinitroaniline or N-butyl-acetamide. With N2O4, smaller amounts of N-nitroamines form concurrently and increase with decreasing amine basicity. The results are discussed in relation to amine nitrosation by N2O3 and N2O4 in aqueous acidic solutions. It is suggested that the lower selectivity for the dissolved gaseous reagents may relate to the presence of more reactive N2O3 and N2O4 isomers. The results also show that carcinogenic N-nitrosoamines form under a much wider range of experimental conditions than previously known, some of which are relevant to atmospheric pollution.
TL;DR: The MBS procedure was simpler to perform, could more easily be adapted to large-scale work, and gave more reproducible results, and the conjugates produced were able to detect slightly lower concentrations of first antibody.