Showing papers on "Reagent published in 1975"

Tertiary Phosphane/Tetrachloromethane, a Versatile Reagent for Chlorination, Dehydration, and P ? N Linkage

Abstract: In this review the processes occurring on the treatment of triphenylphosphane with tetrachloromethane are first reported; a key role is played here by (trichloromethyl)phosphonium chloride which reacts with a further amount of the phosphane to give the stable salt [chloro(triphenylphos-phoranediyl)methyl]triphenylphosphonium chloride by way of dichlorophosphorane and (dichloromethylene)phosphorane that is detectable only as an intermediate. The preparative application of the two-component system as a chlorinating, dehydrating, and P—N-linking reagent is ascribable to “phosphorylation” of the substrate in question through several reactive species. In these applications the reactions with the substrate compete with reactions of the two-component system with itself, so that the overall course of the reaction is in nearly all cases much more complex than was previously assumed. Nevertheless. very good results can be achieved by the use of this reagent, high yields and mild reaction conditions being characteristic.

The Preparation and Synthetic Utility of tert-Butyldiphenylsilyl Ethers

Abstract: The utility of tert-butyldiphenylsilyl chloride as a reagent for the protection of hydroxyl groups was explored. The corresponding tert-BDPSi ethers have much greater stability to acids, and under ...

A simplified phosphorus analysis technique.

Abstract: A simplified method for the analysis of total P(TP), total dissolved P(TDP) and dissolved reactive P (DRP) in multiple water samples has been developed. The reported modification utilizes a single digestion reagent and a single "mixed reagent" to eliminate neutralization, transfer and dilution steps normally required in total P analyses. The method results in a 70 percent decrease in analysis time for multiple samples, a reduction in the glassware required, and about a 30 percent increase in sensitivity. The method can be directly applied to water samples with P levels of 2 to 1100 ug P/l. Reproducibility and precision measurements compare to or exceed commonly used P techniques.

Enzymatic immunological method for the determination of antigens and antibodies

Abstract: The present invention relates to improvements in the sandwich technique for the determination of a component of an antigen-antibody reaction in a liquid sample to be tested, utilizing as reagents (a) one component of said reaction bound to the surface of a water-insoluble, water-insuspensible, solid carrier, and (b) a component having the same immunological properties covalently linked to an enzyme. The liquid sample is contacted and incubated with the reagent(s) to form a reaction mixture, the enzyme activity of either the liquid or solid phase of which is a measure of the presence and quantity of the component to be determined. The method is especially useful for diagnostic testing for hepatitis or rubella antibodies.

Interferences in the determination of elements that form volatile hydrides with sodium borohydride using atomic-absorption spectrophotometry and the argon-hydrogen flame

Abstract: A study has been made of the determination of arsenic, bismuth, germanium, antimony, selenium, tin and tellurium by conversion into the hydrides by reaction with sodium borohydride in dilute hydrochloric acid followed by measurement with atomic-absorption spectrophotometry in an argon-hydrogen flame. A general study, involving 48 elements, of interferences has been carried out and it has been shown that significant interference occurs in many instances but that the procedure is simple to carry out and gives a considerable increases in sensitivity and detection limits for the elements listed, with the exception of tin, for which high blank values were obtained owing to the presence of tin in the sodium borohydride reagent.

The reduction of mono-coordinated molecular nitrogen to ammonia in a protic environment

Abstract: WE have reduced ligating molecular nitrogen (dinitrogen) to ammonia in yields of up to 90% at a single metal site This reaction is important for its possible application to our understanding of the chemical mechanism of the reduction of dinitrogen to ammonia by nitrogenase, where the reduction may occur at a single molybdenum ion site1 Our reaction occurs when compounds of the type [M(N2)2(PR3)4](I; M =Mo or W; R = alkyl or aryl) are treated at room temperature with sulphuric acid in methanol solution: This reaction was performed in a vacuum so that the evolved gases could be analysed and measured On mixing the reagents, one molecule of nitrogen gas was rapidly evolved with a trace of dihydrogen The remaining dinitrogen was spontaneously reduced to ammonia together with some hydrazine, presumably also with concomitant oxidation of the metal M

Synthesis of olefins. Cross-coupling of alkenyl halides and Grignard reagents catalyzed by iron complexes

Abstract: Grignard reagents are coupled with alkenyl halides such as 1-bromopropene and P-bromostyrene in the presence of catalytic amounts of iron(II1) complexes to afford alkenes. This cross-coupling reaction can be employed as a synthetic route for alkenes, in which primary, secondary as well as tertiary alkyl groups like isopropyl, cyclohexyl, and tert-butyl Grignard reagents are utilized. The reaction is stereospecific since trans-1-bromopropene affords only transbutene-2 with methylmagnesium bromide and iron(II1) pivalate. Furthermore, the rearrangement of branched alkyl groups such as tert-butyl has not been observed with an iron catalyst. Among various iron(II1) complexes examined, tris(dibenzoylm'ethido)iron(III) is the most effective from the standpoint of rates and deactivation. Product and spectral studies suggest that the active catalyst is a labile iron species derived by reduction of iron(II1) in situ by the Grignard component. High rates of cross coupling are limited by deactivation of the catalyst due to an aging process attributed to aggregation of the active iron species. Several mechanistic schemes are considered for cross coupling including (a) oxidative addition of alkenyl halide to a low valent alkyliron species followed by reductive elimination of the cross-coupled product and (b) assistance by reduced iron in the concerted displacement of halide at the alkenyl center by the Grignard reagent.

A reporter group delivery system with both absolute and selective specificity for thiol groups and an improved fluorescent probe containing the 7-nitrobenzo-2-oxa-1,3-diazole moiety

Abstract: 1. 4-(N-2-Aminoethyl2'-pyridyl disulphide)-7-nitrobenzo-2-oxa-1,3-diazole (compound I) was synthesized and evaluated as a fluorescent labelling reagent for thiol groups. 2. The design of compound (I) as one example of a general type of reporter group delivery reagent (2-pyridyl-S-S-X, where X contains an environmentally sensitive spectroscopic probe) is discussed. 3. The electronic absorption spectrum of compound (I) was determined over a wide range of pH and the spectral changes that accompany its reaction with low-molecular-weight thiols, e.g. L-cysteine, and with papain (EC 3.4.22.2) and bovine serum albumin are discussed. 4. A new value of epsilon343 for 2-thiopyridone (Py-2-SH) was determined as 8.08 X 10(3) +/- 0.08 X 10(3)M-1-cm-1. 5. Spectral analysis of the reactions of compound (I) with L-cysteine and with papain (in the pH range 3.5-8.0) showed that even under equimolar conditions the reaction (thiol-disulphide interchange to release Py-2-SH) is essentially stoicheimoetric and probably proceeds by specific attack at the sulphur atom distal from the pyridyl ring of compound (I). 6. The fluorescence-emission spectra of compound (I) and of the products of its reaction with papain and with ficin (EC 3.4.22.3) were determined. Compound (I) is highly fluorescent in aqueous solution. Excitation within the intense visible absorption band (lambda max. 481 nm, epsilon max. 2.52 X 10(4)M-1-cm-1) provides green fluorescence with an emission maximum at 540 nm. Both papain and ficin labelled by reaction with compound (I) are characterized by fluorescence-emission maxima (535 nm and 530 nm respectively) of even higher intensity. The fluorescence emission of the product of the reaction of papain with compound (I) was shown to be 25 times more intense than that of the product of the reaction of papain with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (Nbd chloride). 7. The second-order rate constants (k2) for the reactions of compound (I) and of Nbd chloride with GSH, papain, albumin, ficin, 2-benzimidazolylmethanethiol and 2-benzimidazolylethanethiol were determined at 25.0 degrees C and various pH values. At pH4 the values of k2(compound I)/k2(Nbd chloride) are: GSH, 288; albumin, 36; papain 3 X 10(3); ficin, 3 X 10(4). 8. The pH-k2 profiles for the reactions of compound (I) and of Nbd chloride with the two 2-benzimidazolylalkanethiols were determined. Of the four profiles only that for the reaction of compound (I) with 2-benzimidazolylmethanethiol is characterized by a striking rate maximum in acidic media.

New Colorimetric reaction for end-point, continuous-flow, and kinetic measurement of urea.

Abstract: A reaction of urea, o-phthalaldehyde and N-(1-naphthyl)ethylenediamine is described for measurement of urea by manual, continuous-flow, and kinetic methods. The continuous-flow system requires 25 mu-l of sample; 40 samples can be analyzed per hour. The kinetic method requires no enzymes, has no lag phase, and has good sensitivity. A major advantage of the reaction is that it occurs at a temperature of 37 degrees C or lower. The results obtained by all three methods agree well with those for a continuous-flow procedure in which diacetyl is a reagent.

Dispersants and process for their preparation

Abstract: Compositions useful as lubricant and fuel dispersants are prepared by reacting a hydroxyaromatic compound containing an aliphatic or alicyclic substituent which has at least about 6 carbon atoms with an aldehyde in the presence of an alkaline reagent and at a temperature up to about 125°C., substantially neutralizing the resulting intermediate at a temperature up to about 150°C., and then reacting with a primary or secondary amino compound.

P-Azidophenacyl bromide, a versatile photolabile bifunctional reagent. Reaction with glyceraldehyde-3-phosphate dehydrogenase.

Abstract: The synthesis of the photochemically labile bifunctional reagent p-azidophenacyl bromide (1) is described. This compound may be covalently attached to a known site of an enzyme or other macromolecule by nucleophilic displacement at the alpha-bromo ketone moiety. Subsequent irradiation of the bound reagent gives a nitrene which may insert into a second portion of the enzyme forming a cross-link. Regeant 1 proved to be an excellent inhibitor of rabbit muscle glyceraldehyde-3-phosphate dehydrogenase.

Singlet oxygen: a reagent in organic synthesis

Abstract: In the introduction, the generation, the electronic state and the reaction of singlet oxygen ( 1 O 2 ) with carbon-carbon double bonds is described. For preparative purposes, 1 O 2 is generated by dye-sensitized excitation of oxygen ( 3 O 2 ). The photo-oxygenation reaction leads to the formation of peroxides, which can be used as intermediates in the organic synthesis. Described are processes of preparation of important flavours and fragrances : inter alia , the synthesis of ascaridole ( 8 ), pear ester ( 24 ), galbanolene ( 25 ), rose oxide ( 73 and 74 ), damascenone ( 83 ), nootkatone ( 97 ), norcetone 100 from vetiver oil, geijerone ( 105 ) and the new musk fragrance 2,5-dioxacyclohexadecan-1, 6-dione ( 111 ). The role of 1 O 2 as a biomimetic agent is mentioned in a few examples.

Quantitative method using differential infrared spectrometry for the determination of compound types absorbing in the carbonyl region in asphalts

Abstract: A method for the qualitative and quantitative determination of ketones, dicarboxylic anhydrides, carboxylic acids, and 2-quinolone types in asphalts is presented. The technique is based on differential infrared spectrometry combined with base hydrolysis and silylation reactions. Determinations are made using simple laboratory equipment without the necessity of reagent or reaction product separation. The method was applied to a collection of asphalts to show the effect of oxidation in road service on the production of the title compound types. Ketones were found to be the major oxidation product absorbing in the carbonyl region. Dicarboxylic anhydrides were formed on oxidation in considerably greater amounts than carboxylic acids. 2-Quinolones were not formed on oxidation. Significant amounts of ketones and detectable amounts of carboxylic anhydrides were not found in fresh, unoxidized asphalts although carboxylic acids and 2-quinolone types were often present. (auth)

Process for producing reactive, homogeneous, self-bondable lignocellulose fibers

Abstract: A novel process for producing reactive, homogeneous, self-bondable lignocellulose fibers is provided in which individual, separate, lignocellulose fibers are oxidatively modified, employing oxidative reagent system. Pursuant to the teachings of the present invention, the oxidative modification step is conducted in a controlled manner, for example, employing a confrication step, using a liquid-phase reagent system, the subject product fibers, prior to sheet formation, being substantially free of residual oxidative reagent. Sheets are formed from the product fibers on subsequent bonding, employing mild formation conditions, the sheets having improved dry- and wet-strength properties.

Method for treatment of digester supernatant and other streams in wastewater treatment facilities

Abstract: Digester supernatants and/or liquors from sludge dewatering are reacted with an excess of an alkaline reagent having a stronger cation than the ammonium ion and the reaction product is separated into a solution containing aqueous ammonia and solids. The aqueous ammonia derived from the separation stage is heated by free steam under a lowered pressure to free ammonia in gaseous form. The ammonia as a gas, or adsorbed in water, or adsorbed in an acid, or as an acid salt is then mixed with conventionally dried sludge to increase the nitrogen content of the sludge from approximately 1-2 percent to as high as 10 percent.

Use of O-p-Nitrobenzyl-N, N′-Diisopropylisourea as a Chromogenic Reagent for Liquid Chromatographic Analysis of Carboxylic Acids

Abstract: O-p-Nitrobenzyl-N, N′-diisopropylisourea was shown to react under relatively mild conditions with carboxylic acids to yield the p-nitrobenzyl esters as chromogenic derivatives useful for liquid chromatographic analysis. The p-nitrobenzyl ester of stearic acid was detectable down to the picomole range.

Novel starch ethers

Abstract: A reagent useful for the chemical modification of starch is prepared by the reaction of a 2,3-dihalopropionic acid or alkyl ester thereof with a secondry amine. The reaction of the reagent with starch, carried out in an aqueous solution under controlled conditions, produces novel amino acid ether derivatives which are characterized by the presence of both a cationic and an anionic substituent group on the same reactive site. The resulting starch ethers are characterized by their stability, their ability to form cooked pastes which are more resistant to gelling upon cooling and their lowered gelatinization temperatues.