High-pressure phase studies on fluid mixtures of low-volatile organic substances with supercritical carbon dioxide

Two high-pressure phase equilibrium cells working according to the analytical method in the temperature range 300 to 450 K and up to 200 MPa have been developed. In the first cell p,T,x,y equilibrium data can be determined by sampling and GC analysis. With this cell the gas-liquid phase behaviour of the ternary systems carbon dioxide + tridecane + hexadecane and carbon dioxide + tridecane + 1-hexadecanol were determined at 423.4 K and between 8 and 35 MPa. For the second apparatus a spectroscopic high-pressure cell fitted with two pairs of sapphire windows was developed. Molar absorptivities are obtained from calibration runs in the homogeneous region. Gasliquid phase equilibria in the system decane + CO₂ were investigated from 342.8 to 400.2 K and between 10 and 20 MPa; here absorption data were measured in the NIR region.     

Pseudohalogenometallverbindungen: LVIII. Reaktionen von diphenylphosphorylazid und perfluor-n-hexylsulfonylazid mit triphenylphosphan-komplexen von platin(0), rhodium(I), iridium(I), ruthenium(0), kobalt(II) und kupfer(I)

Diphenylphosphorylazide N₃P(O)(OPh)₂ reacts with Pt(PPh₃)₃, Pt(PPh₃)₂(C₂H₄), trans-RhCl(CO)(PPh₃)₂, Ru(CO)₃(PPh₃)₂, CoCl₂(PPh₃)₂ and CuCl(PPh₃)₂ to give the azido complexes Pt(PPh₃)₂(N₃)R, Pt(PPh₃)₂(N₃)₂R₂, the urylene complex RhCl(PPh₃)₂(RNCONR) and the phosphine imine complexes Ru(CO)₃(RPPh₃)₂, CoCl₂(RNPPh₃)₂, CuCl(RNPPh₃)₂, respectively, (RP(O)(OPh)₂). The oxidative addition of n-C₆F₁₃SO₂N₃ to Pt(PPh₃)₄ and Pt(PPh₃)₂(C₂H₄) affords the complexes Pt(PPh₃)₂(N₃)R and Pt(PPh₃)₂(N₃)₂R₂, respectively, (RSO₂C₆F₁₃. The compounds are characterized by elemental analysis and by their IR spectra.     

The generalized standard addition method: intermetallic interferences in anodic stripping voltammetry

A barrier to routine application of anodic stripping voltammetry is the possible formation of intermetallic compounds which can lead to significant errors in the estimated analyte concentrations. As the method of standard additions can correct only for matrix effects, it is powerless to correct for intermetallic interferences which are not matrix effects. By changing the experimental design, the new generalized standard addition method can simultaneously characterize and correct for this type of interference as well as matrix effects expected for real samples. The method is tested on the Cu—Zn—Hg system and error estimates are provided for calculated linear response constants and analyte concentration.     

A single-fluor approach to DNA sequence determination using high performance capillary electrophoresis.

The Tabor and Richardson strategy for enzymatic chain termination sequencing of DNA using relative peak intensity has been adapted to high performance capillary gel electrophoresis with laser induced fluorescence detection. This approach to DNA sequencing involves the use of only a single fluor and results in significant reduction in the time required to determine a DNA sequence without the use of highly complicated and expensive instrumentation. We present a modification of the Tabor and Richardson approach employing two reactions, each containing complementary mixtures of only three ddNTP's in the concentration ratio 4:2:1. The DNA sequence is determined by relative peak height and by assigning the missing ddNTP to "gaps" between the peaks. The use of only three terminators/reaction simplifies the software task of differentiating between the termination types and makes more efficient use of the available dynamic range. Both complementary mixes generate complete sequence information and the two data files are combined in order to make a more confident sequence call. This process helps to eliminate errors caused by occasional non-uniform incorporation of ddNTP's or false terminations and also alleviates some of the difficulty associated with reading through compressed regions of the electropherogram.     

Sample evaporation in conventional GC split/splitless injectors. Part 1: Some quantitative estimates concerning heat consumption during evaporation

During sample evaporation in conventional vaporizing injection, the supply of heat to the evaporating liquid is a problem, first because the amounts of heat consumed are relatively large and, secondly, because the heat must be transferred to the sample within a very short time. Times available for evaporation, required amounts of heat, possible sources of heat, and the time required to transfer the heat to the sample liquid are discussed. It is shown that mixing with carrier gas contributes little heat to the evaporation process, but also that packings with glass wool have too low a heat capacity to deliver the required amount of heat to the evaporating sample. Transfer of heat from the insert wall to the sample easily requires several seconds, even if cooling of the vaporizing zone by 20° is accepted. Thus “flash evaporation” is usually impossible and most liquids must be held in the vaporizing chamber to allow full evaporation.     

Sample evaporation in conventional split/splitless GC injectors. Part 3: Retaining the liquid in the vaporizing chamber

As most sample liquids tend to pass through an empty injector insert at a speed which is too high to enable complete evaporation, movement of the liquid must be arrested before it reaches the column entrance. Stopping the liquid means deposition on to a surface; this, however, is possible only after the temperature of the surface has been cooled to (or below) the boiling point of the liquid (solvent). The performance of different means of stopping the liquid has been tested visually (by the method described in Part 2). Baffles on the wall of the injector insert had hardly any effect on evaporation: the band of liquid leaving the syringe needle performed a perfect slalorn around them. The inverted cup proved more efficient, but the best performance was obtained from a light plug of glass wool: owing to its low thermal mass, the first fibers to be met by the liquid are immediately cooled to the solvent boiling point, allowing the liquid to wet it. The sample liquid is sucked up by the glass wool, from where the sample evaporates relatively slowly, often over a period of several seconds.     

N,N-Bis(halomethyldimethylsilyl)acetamides and their reactions

N,N-Bis(halomethyldimethydimethylsilyl)acetamides, MeCON(SiMe₂CH₂X)₂, (X = Cl, Br) were prepared by transsilylation of N,O-bis(trimethylsilyl)acetamide with halomethyldimethylchlorosilane. With water and methanol, instead of the expected SiN cleavage, nucleophilic substitution of halogen took place and the products were 1-acetyl-2,2,6,6-tetramethyldisilamorpholine and N,N-bismethoxymethyldimethylsilyl)acetamide respectively. These compounds were shown by IR and ¹H NMR spectra to have the N,N-disilylacetamide structure. Thermodynamic, kinetic constants of hindered rotation around the CN bond in these compounds were determined from their temperature-variable ¹H NMR spectra. The main products of thermolysis of the silylamides are α,ω-dichloropolydimethylsiloxanes and polydimethylcyclosiloxanes.     

Modification of the Cp′ ring in the ferrocifen precursor and its influence on the recognition by the estrogen receptor

A synthetic pathway giving access to diphenyl ethylene organometallic derivatives possessing the ferrocifen precursor skeleton modified in the Cp′ ring is described. It relies on reaction of the (η⁵-propionylcyclopentadienyl) (η⁶-benzene)iron(II) salt 7 with substituted cyclopentadienyl anions or their heteroanalogs followed by the McMurry coupling reaction with 4,4′-dihydroxybenzophenone. Using this approach pentamethylcyclopentadienyl and 3,4-dimethylphospholyl analogs of ferrocifen precursor (10 and 11) have been synthesized. Even with the presence of the bulky and containing phosphorus η⁵-ligands these compounds are still recognized by the two subtypes of estrogen receptor(ERα and ERβ).