Search results for "solution"

ChemInform Abstract: Electrical Breakdown and Pitting in Anodic Films on Tungsten in Halogen Ion-Containing Solutions.

1988

Abstract The systematic investigation of the anodic behaviour of W in halogen ion-containing solutions reveals noticeable differences in the presence of different anions. Strong generalized dissolution is observed in fluoride solutions, the oxide growth being hindered at low anodizing current densities. Sparking phenomena occur in the presence of Br− and I− anions as in nitrate and sulphate solutions. Only in Cl− containing solutions is the growth of the anodic films limited by the occurrence of pitting phenomena at a critical thickness of the oxide. The laws of dependence of the phenomenon on the experimental parameters and the influence of ferrous ions on the voltage at which pitting occu…

Conformational study of methyl esters of some aliphaticerythro- andthreo-dichlorocarboxylic acids

1984

The average conformations of methyl esters of some aliphatic erythro- and threo-dichlorocarboxylic acids in dilute carbon tetrachloride solutions have been determined from the vicinal proton–proton coupling constants and 1H NMR shifts. The 13C shift differences between the erythro and threo forms are compared and discussed with regard to the differences in the average conformations.

Cyclic Sulfonimidates by Dynamic Diastereomer-Differentiating Cyclisation: Large-Scale Synthesis and Mechanistic Studies

2001

A dynamic diastereomer differentiating cyclisation is the key step in a new large-scale synthesis of both enantiomers of the cyclic sulfonimidates 1 (Aldrich no. 54099-4) and ent-1 (Aldrich no. 54412-4). These are valuable starting materials in the asymmetric synthesis of chiral oxa- and azaheterocyclic compounds. NMR spectroscopic studies on the reacting system reveal N-chloro sulfinamides to be reactive intermediates in the oxidative chlorination of sulfinamides with tert-butyl hypochlorite and allow for the inspection of the configurational behaviour of the involved sulfonimidoyl chlorides and sulfonimidoyl bromides.

Die stufenweise Syntheseo,o?-methylenverbr�ckter Cyclohexamerer mitp-Kresol- oderP-Kresol- und 4-tert-Butylphenol-Bausteinen Vergleich mit �hnlich st…

1981

Two phenolic alcohols with six phenolic units in their molecules have been obtained by stepwise syntheses starting from simple phenolic derivatives. The phenolic alcohols were cyclized in a one step cyclization by boiling in a very diluted acetic acid solution. A two step cyclization of a phenolic alcohol with three phenolic units to a cyclohexamer proceeds only with poor yields. The cyclic compounds were compared with chainlike oligomers containing six phenolic units in their molecules.

Immobilisation of humic substances

2002

Attempts were made to immobilise humic substances (HS) by grafting them onto different carriers (styrene-divinylbenzene copolymers, cellulose and silica) as well as by their crosslinking with formaldehyde. Reaction with Merrifield resin was used for the immobilisation of HS, coupling by means of water-soluble carbodiimides to carriers containing amino-groups. Crosslinking of HS with formaldehyde (also in presence of other substances able to enter polycondensation reactions with formaldehyde) was shown to be an efficient method for their insolubilisation. Properties of the obtained immobilised HS were studied, including their potential use as sorbents for several metal ions and organic subst…

1992

Phosphonomethyl-substituted phenols are readily obtained from o-hydroxymethylated phenols and trialkyl phosphites. The free acids, incorporated into phenol-formaldehyde resins, act as cation exchangers with remarkable selectivity for different metal ions.

Cation-induced self-assembly of an amphiphilic perylene diimide derivative in solution and Langmuir–Blodgett films

2015

Abstract A novel amphiphilic perylenetetracarboxylic diimide (PDI) derivative, N-(4′-benzo-15-crown-5-ether)-N-hexyl-1,7-di(4-tert-butyl-phenoxy)perylen-3,4,9,10-tetracarboxylic diimide (15C5PDI), has been synthesized and characterized. Dimerization of 15C5PDI is induced in CHCl 3 solution with the present of K + , resulting in the formation of the slipped co-facial J -aggregates, as revealed by absorption and fluorescence spectroscopies. Analysis of the surface pressure–area ( π – A ) isotherms and spectral change for the monolayer formed at the air/water interface, disclosed that 15C5PDI molecules adopted the H -type aggregation mode with a face-to-face configuration and edge-on orientati…

Synthesis and characterization of a new Organic – Inorganic sulfate (C5H6N2O)2[Co(H2O)6]3(SO4)4.2H2O

2014

crystals of a new hybrid compound, (C 5 H 6 N 2 O) 2 [Co(H 2 O) 6 ] 3 (SO 4 ) 4 .2H 2 O, were synthesized in aqueous solution and characterized. This compound crystallizes in the triclinic system with the space group P-1, the unit cell :a=6.632(3) A, b=11.769(5) A, c=14.210(6) A, α=67.86(4)°, β=81.32(4)°, γ=85.18(4)° and V=1015.14(8) A 3 . Its crystal structure can be described as a packing of alternated inorganic and organic layers. The different components are connected by a three-dimensional network of O-H…O and N-H…O hydrogen bonds.

Crystal Structures and Thermal Behavior of Bis(dibenzyldimethylammonium) Tetrabromometallates(II) [M = Mn(II), Co(II) and Zn(II)] and Their Solvates

2007

Six new A2MBr4 structures [A = dibenzyldimethylammonium cation,M = Mn(II), Co(II) or Zn(II)] were crystallized with or without solvent molecules from acetonitrile, methanol and/or aqueous solutions. The isomorphous compounds [(Bz2Me2N)2][MnBr4]·CH3CN·H2O (1) and [(Bz2Me2N)2]-[ZnBr4]·CH3CN·H2O (4) crystallize in the triclinic space group P1̄ from acetonitrile solutions. The solvent molecules participate in the hydrogen bonding network inside the crystal structure. [(Bz2Me2N)2][CoBr4]·0.5CH3CN (2) crystallizes from an acetonitrile solution in the monoclinic space group P21/c. The solvent molecules fill the voids of the crystal structure. Compound 2 is isostructural with the previously reporte…

ChemInform Abstract: Alkaloid Determination in Crude Extracts from Cortex Quebracho and Opium Applying Capillary Electrophoresis and Capillary Electr…

2010

The applicability of capillary electrophoresis with UV and electrospray ionisation (ESI)-mass spectrometric detection to the determination of alkaloids in crude extracts of Cortex Quebracho and opium has been investigated. The use of a buffer electrolyte consisting of aqueous ammonium acetate (pH 3.1) and acetonitrile resulted in a high performance of peak resolution. Most of the alkaloids have been identified according to the signal of the protonated molecular ion in the ESI mass spectrum