Complexometric estimation of copper

Summary Copper(II) or Copper(II) and iron(III) in a mixture are determined by titration with EDTA (disodium salt) solution as complexometric reagent at p_H 4.0 using potassium thiocyanate-p-anisidine as an indicator.Fe^III is estimated in the mixture by titration with EDTA (disodium salt) solution using potassium thiocyanate-ether as an indicator.Cu^II present in the mixture is, therefore, equivalent to the difference in amounts of the EDTA (disodium salt) used for the two sets of titrations of the mixture using potassium thiocyanate-p-anisidine and potassium thiocyanate-ether as indicators respectively.Strontium, magnesium, manganese, calcium, barium and mercuric ions do not interfere in these estimations.

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Zusammenfassung Kupfer(II) oder Kupfer(II) und Eisen(III) zusammen werden komplexometrisch mit ÄDTA-Lösung bei p_H 4,0 unter Verwendung von Kaliumthiocyanat-p-Anisidin als Indicator titriert. Eisen(III) wird in dem Gemisch durch komplexometrische Titration gegen Kaliumthiocyanat-Äther als Indicator bestimmt. Der Kupfer(II)-gehalt ergibt sich aus der Differenz der beiden Titrationen. Strontium, Magnesium, Mangan, Calcium, Barium und Quecksilber(II) stören nicht.

     

Reduction of Z-2-chlorostilbene with lithium aluminum hydride: evidence for an electron transfer radical mechanism

$\text{Z}$-2-Chlorostilbene undergoes uncatalyzed LiAlH₄ reduction giving phenanthrene and $\text{Z}$-stilbene. An electron transfer radical mechanism is proposed. LiAlH₄ induced isomerization of $\text{Z}$-stilbene produces $\text{E}$-stilbene.     

Chromatographic study of anionic complexes

Summary In this paper we have reported our results on the attempted separation of copper(II), nickel(II), cobalt(II) and iron(III) in mixtures by filter paper strip chromatography, using aqueous ethanol as solvent. The effect of the presence of varying concentrations of citrate ion as a complexing agent in the mixtures has been studied. The complexing agent has been added in the metal solution, and not in the solvent as usually done by previous workers.     

Photoaffinity labeling of bovine rhodopsin

Photoaffinity labeled (3-diazoacetoxy)-9-cis-retinal (1) and (9-methylenediazoacetoxy)-9-cis-retinal (20) were synthesized and bound to absorption maxima at 465 and 460 nm respectively. Binding studies established that synthetic retinals 1 and 2 bind to the natural binding site and that the integrity of the diazoacetoxy photoaffinity label is preserved in the process. Incorporation of 3-(O¹⁴COCHN₂)-labeled 9-cis retinal could be conveniently carried out in high yield using apomembrane solubilized in CHAPS as detergent to afford the pigment analog in a pure form. Photolysis of the diazoacetoxy group within the binding site led to 15–20%, crosslinking of rhodopsin as estimated by using radiocarbon containing labeled retinal 1 thus showing that this synthetic retinal is suitable for photoaffinity labeling of the active site in rhodopsin. Subsequent experiments to establish the site(s) of crosslinking by sequencing studies will then contribute to our knowledge of the structure of rhodopsin.     

Cumulative yields of short-lived isotopes of barium in the spontaneous fission of252Cf

Cumulative yields of short-lived/barium isotopes^{139, 141, 142}Ba have been determined in the spontaneous fission of²⁵²Cf, using fast radiochemical separation and gamma-ray spectrometry.¹⁴²Ba yield is reported for the first time. The measured cumulative yields are converted to chain yields, assuming normal charge distribution systematics for comparision with the literature data.     

Improved highly efficient synthesis of α,β-acetylenic ketones. Nature of the intermediate from the reaction of lithium acetylide with boron trifluoride etherate

A wide variety of α,β-acetylenic ketones were synthesized in very high yields via an exceptionally facile intermolecular reaction of lithium alkynyltrifluoroborates and carboxylic acid anhydrides.     

Nucleotide. XV. Synthese und Eigenschaften von 2′-O-t-Butyldimethylsilyl-5′-O-monomethoxytritylribonucleosid-3′-phosphotriestern,Ausgangssubstanzen für Oligonucleotid-Synthesen

Nucleotides. XV. Synthesis and Properties of 2′O-t-Butyldimethylsilyl-5′-O-monomethoxytritylribonucleoside-3′-phosphotriesters, Starting Materials for Oligonucleotide Syntheses The syntheses of two types of fully blocked ribonucleoside 3′-phosphotriesters 6–14 have been achieved in excellent yields from 2′-O-t-butyldimethylsilyl-5′-O-monomethoxytrityl-ribonucleosides 1–5 by phosphorylation with 2-chloro- and 2,5-dichlorophenylphosphorodichloridate respectively and subsequent treatment by cyanoethanol to 6 , 8 , 10 , 12 and 14 and by p-nitrophenylethanol to 7 , 9 , 11 and 13 . These phosphotriesters are valuable starting materials for oligonucleotide syntheses due to the fact that the corresponding phosphotriesters 15–23 with free HO? C(5′) could be obtained by detritylation and the 3′-phosphodiester triethylammonium salts 24–32 by deblocking of the cyanoethyl and the 2,5-dichlorophenyl group respectively. All newly synthesized compounds have been characterized by UV.-and NMR.-spectra as well as C, H, N elementary analyses.     

Photochemical and thermal transformations of carboxylic dithiocarbamic anhydrides and acyl xanthates

The reaction of diphenylchloroacetyl chloride with different dithiocarbamates gave the corresponding dithiocarbamic anhydrides. Under analogous conditions, dithiocarbamyl phenylacetic acids and dithiocarbamyl acetic acids were formed from the reaction of dithiocarbamates with phenylchloroacetyl chloride and chloroacetyl chloride, respectively. O-Ethyl S-acyl xanthates were formed from the reaction of potassium O-ethyl xanthate with diphenylacetyl chloride, diphenylchloroacetyl chloride, cyclopentylphenylacetyl chloride and triphenylacetyl chloride. Photolysis of dithiocarbamic anhydrides gave a mixture of products consisting of 1,2-dichlorotetraphenylethane, carbon monoxide and the corresponding thiocarbamoyl sulfides. Acyl xanthates, on the other hand, gave carbon monoxide and the corresponding substituted ethane derivatives. When dithiocarbamic anhydrides were refluxed in hydroxylic solvents such as methanol, ethanol and n-propanol, the corresponding dithiocarbamyl acetates were formed. Thermal decomposition of acyl xanthates gave carbon disulfide and the corresponding esters.     

Synthesis of some new fluorine containing 3-dialkylaminomethyl indoles, 3-indolylglyoxamides and tryptamines

Several new 2-(fluoroaryl)-3-dialkylaminomethylindoles, 3-acetyl-2-(fluoroaryl)-indoles, 2-(fluoroaryl)-3-indolylglyoxamides and corresponding tryptamines have been prepared as possible psychopharmacological agents. 2-(Fluoroaryl)-indoles have been synthesized by theFischer indole synthesis. 2-(Fluoroaryl)-indoles on treatment with oxalyl chloride and subsequent reaction with amines, gave 2-(fluoroaryl)-3-indolylglyoxamides. Some of these indolylglyoxamides were reducted with lithium aluminium hydride, to the corresponding tryptamines. 2-(Fluoroaryl)-indoles when subjected toMannich reaction afforded 3-dialkylaminomethyl-2-(fluoroaryl)-indoles. All these new compounds have been characterized by IR spectral studies.Possible Psychopharmacological Agents, Part XII, Part XI, J. Indian. Chem. Soc.57, 423 (1980).     

Thiotropolone as a chromogenic reagent for the simultaneous determination of cobalt(II) and nickel(II)

Thiotropolone forms chloroform-soluble reddish-brown and violet complexes with cobalt(II) and nickel(II), in the pH range 7.0-8.5 and 6.0-9.0 respectively. Based on this, a sensitive and rapid method for the spectrophotometric determination of traces of cobalt and nickel in metals and alloys has been developed. The two metals can be determined accurately in the range 0.6-2.6 ppm of cobalt and 0.75-4.57 ppm of nickel, simultaneously.