Zur Katalysierten Verflüchtigung von rotem Phosphor und von Claudetit

The Catalysed Volatilization of Red Phosphorus and of Claudetite The catalysis of the volatilization of P_red (as P₄) by AlCl_3,g, and of the volatilization of claudetite (as As₄O₆) by I_2,g is observed by mass spectrometry.     

Seed gum ofStryphnodendron barbatiman (barbatimão)

Stryphnodendron barbatiman (barbatimão) is a native tree that is found throughout the “Cerrados,” a region of Central Brazil. Plant seeds, on water extraction, furnished 28 g% galactomannan (dryweight basis), the monosaccharide composition of which (galactose to mannose ratio, 1.0:1.5) fits in the legume heteromannan group. This seed gum, after Sevag deproteinization, still retained 6 g% of associated protein and had a molecular weight of about 1.8 MD on gel filtration. A high intrinsic viscosity (1300 cP) was observed for the polysaccharide sample obtained after reflux of the crushed seeds in 80% aqueous methanol.

     

Zur Theorie der Chiralitätsfunktionen

The Algebraic Theory of Chirality Functions is derived by means of exclusively qualitative considerations. Hence, the significance of quantitative results is questionable. Moreover the construction of “Näherungsansätze” (”Approximation-Ansatz”), which may be interpreted as semiempirical methods, is achieved on the basis of plausibility and mathematical simplicity. Since physical arguments are not included, the consistency or inconsistency of “Näherungsansätze” with experimental results do not justify direct physical conclusions.     

The 6Li,6Li-INADEQUATE Experiment: A New Tool for 1D- and 2D-NMR Studies of Organolithium Compounds

The 1D- and 2D-⁶Li, ⁶Li-INADEQUATE experiments are described as new tools for the detection of scalar coupled nonequivalent ⁶Li nuclei in organolithium clusters. Practical applications of these sequences are demonstrated for the ⁶Li-NMR spectra of (E)-1-lithio-2-(2-lithiophenyl)-1-phenylhex-1-ene ( 1 ) and (E)-2-lithio-1-(2-lithiophenyl)-1-phenylpent-1-ene ( 2 ), where signals due to dimers and monomers can be distinguished. The performance of the 2D-⁶Li, ⁶Li-INADEQUATE and the ⁶Li, ⁶Li-COSY-45-LR experiment are compared. The ⁶Li chemical shifts of 1 and 2 are discussed.     

HPLC-NMR of fatty alcohol ethoxylates

The application of HPLC-NMR for the analysis of a mixture of fatty alcohol ethoxylates (FAEs) is described. The use of the new generation, cryogenically cooled probes is investigated in respect of the sensitivity advantage that they provide. The FAE mixture is separated using liquid chromatography at the critical point of adsorption. The ability of the method to differentiate between the different end groups and the degree of polymerization of the mixture constituents is investigated. Both on-flow and stop-flow HPLC-NMR techniques were used together with two-dimensional NMR spectroscopy. The results are compared with those obtained by using an evaporative light scattering detector for the HPLC.     

Der chemische Transport von Platin mit Chlor. Experimentell bearbeitet mit Marita Trenkel

The Chemical Transport of Platinum with Chlorine Experiments show that the chemical transport of platinum by means of chlorine within a temperature gradient at temperatures below ≈ 1000°K goes into the hot temperature region, but at higher temperatures in the reverse direction. From the thermodynamic discussion it can be seen, that the platinum content of the gas phase at low temperatures is governed by the exothermic formation of Pt₆Cl_12,g, and at higher temperatures by the endothermic formation of PtCl_3,g and PtCl_2,g. The platinum content of the gas phase passes a minimum at ≈ 1000°K, if P(Cl₂) = 3.5 atm. This result is in agreement with the observed inversion of the transport direction.     

Massenspektrometrische Beobachtungen und chemische Transportexperimente mit den Systemen VCl3/Al2Cl6 und VCl2/Al2Cl6

Mass Spectroscopic Observations and Chemical Transport Experiments with the Systems VCl₃/Al₂Cl₆ and VCl₂/Al₂Cl₆ By mass spectrometry the equilibrium VCl_3,s + 0.5 Al₂Cl_6,g ? VAlCl_6,g has been determined: ΔH°(298) = 25.6(±0.5) kcal; ΔS°(298) = 23.0(±3) cal/K, ΔCp (assumed) = ?4 cal/K. This is approximately in agreement with results determined by ligand field spectroscopy by ANUNDSKÅS and ØYE (A. and Ø.). For the dimerization of VCl_3,g values for ΔH and ΔS have been derived. The molecule VAl₂Cl₉ assumed by A. and Ø. could not been observed by mass spectrometry. For the VCl₂/Al₂Cl₆ complex, observed by chemical transport, A. and Ø. give the formula VAl₃Cl₁₁. This molecule could not been observed by mass spectrometry. This suggests a smaller concentration, compared with the results of A. and Ø. Stabilization of VCl_2,s (by metal-nietal-bonds) shifts the reaction to the left, whith explains the lower complex concentration as well as the larger molecular weight of the complex. With chlorides stabilized by stronger metal-metal bonds (MoCl₃, MoCl₂, Nb₃Cl₈) AlCl₃ complexes are not formed in observable concentrations. The chemical transport of VCl₂ with Al₂Cl₆ needs relatively high temperatures (973 → 873 K). In this case the addition of SiCl₄ hinders the attack of the quartz ampoule by Al₂Cl₆. Using a VCl₃ + VCl₂ mixture, VCl₃ is transported by Al₂Cl₆ (673 → 623 K) into the colder region. If afterwords the ampoule is reversed, VCl₃ again moves into the colder region, but the thermal decomposition of VCl₃ at the same time causes that a VCl₂-residue remains in the hot region.     

Tetramethylammonium-calcium-triazid. Darstellung und Kristallstruktur

[N(CH₃)₄]Ca(N₃)₃,M=240.29, was prepared from aqueous solutions of tetramethylammoniumazide with calciumazide at 298 K. The crystals are tetragonala=936.6(7) pm,c=694.7(5)pm, space group P4/nmm,Z=2, (x)=1.31Mgm^–3. The crystal structure was determined by single crystal x-ray diffraction (234 Mo-K-reflections, =0.469 mm^–1,R=0.064). Calcium is octahedrally coordinated to six azide groups. The octahedra are connected via azide groups to a threedimensional array with the complex ammonium ions between. The terminal nitrogen atoms of the azide groups and the methyl groups are considerably disordered.

     

Die Gasmolekeln Pd2Al2Cl10 und PdAlCl5 als Begleiter von PdAl2Cl8

Gas Molecules Pd₂Al₂Cl₁₀ and PdAlCl₅ as Accompanists of PdAl₂Cl₈ Mass spectrometric observations using a double cell showed that the reaction of gaseous Al₂Cl₆ with solid PdCl₂ besides the known gaseous complex PdAl₂Cl₈ gives PdAlCl₅ and the unexpected complex Pd₂Al₂Cl₁₀. For the equilibrium (with ΔCp? ?1 cal/K) ΔH°(298) = 7.5 kcal/Mol and ΔS°(298) = 5.3 ± 2 cl have been obtained.     

Analytical procedures for quantification of peptides in pharmaceutical research by liquid chromatography–mass spectrometry

Peptide quantification by liquid chromatography–mass spectrometry (LC–MS) combines the high resolving power of reversed-phase (RP) chromatography with the excellent selectivity and sensitivity of mass spectrometric detection. On the basis of comprehensive practical experience in the analysis of small molecules, pharmaceutical research is developing technologies for analysis of a growing number of peptidic drug candidates. This article is a detailed review of procedures based on LC–MS techniques for quantitative determination of peptides. With the focus on pharmaceutical applications several technologies for sample preparation, various aspects of peptide chromatography, important characteristics of ESI–MS, selectivity of MS-detection modes, the large variability of internal standards, and modern instrumentation are discussed. The demand for reliable, robust, sensitive, and accurate methods is discussed using numerous examples from the literature, complemented by experiments and results from our laboratory.