Silylation products of cyclic tri-aminal carbanions and their lithiation

The structure of 1,3,5-trimethyl-1,3,5-triaza-cyclohexane (TMTAC) was determined by single crystal X-ray diffraction and compared with earlier gas-phase data. It shows a preference for an aee-conformation in all phases. Lithiated TMTAC, [(RLi)(2)·(RH)] (1) (R = 2,4,6-trimethyl-2,4,6-triaza-cyclohex-1-yl), was reacted with Et(3)SiCl, Ph(3)SiCl and PhMe(2)SiCl to afford the substituted silanes Et(3)SiR (1), Ph(3)SiR (2) and PhMe(2)SiR (3) in moderate yields. They were characterised by NMR spectroscopy ((1)H, (13)C, (29)Si). 1 reacts with Me(2)SiCl(2) and Ph(2)SiCl(2) to give Me(2)SiR(2) (5) and Ph(2)SiR(2) (6) which were characterised by NMR spectroscopy. 5 was also identified by crystal structure determination. Analogous triple substitution could not be observed by employing trichlorosilanes. Quantumchemical calculations explain this by sterical overcrowding of the silicon atom. The reaction of 1 with SiCl(4) did not yield fourfold substitution but a formal insertion product of SiCl(2) into a C-N bond of the TMTAC ring (2,4,6-trimethyl-2,4,6-triaza-1,1-dichloro-1-sila-cycloheptane, 7) in very small quantities. It was identified by X-ray crystallography and shows an intramolecular Si···N dative bond. The reactions of (3) and (5) with n-butyl lithium afforded lithiation of the silicon bound methyl groups in both cases. The products, 8 and 9, were characterised by NMR spectroscopy ((1)H, (13)C, (29)Si), 8 was also characterised by X-ray crystallography.     

Fluorescent conjugated block copolymer nanoparticles by controlled mixing

Monitoring of the formation of stable fluorescent nanoparticles from controlled mixing of a THF solution of poly(fluorene ethynylene)-block-poly(ethylene glycol) in a microfluidic laminar flow crossjunction by spatially resolved fluorescence spectroscopy reveals the time scale of particle formation as well as incorporation of small molecule guests and the role of solvent mixing.     

Intrinsic point defects in niobium: Trapping at100Pd and111In impurities observed by PAC

Radiation-induced lattice defects in high-purity niobium have been investigated in the temperature range of 30K to 540 K by means of - perturbed angular correlation (PAC) measurements using the radioactive probes¹⁰⁰Pd/¹⁰⁰Rh and¹¹¹In/¹¹¹Cd. Both probes were produced within the niobium samples by means of heavy-ion nuclear reactions. At the Pd impurities trapping of defects occurred during heavy-ion irradiation at about 30 K in two defined configurations: defect 1(Pd) withv _Q1=e ² qQ/h=42(±2) MHz, ₁=0 and defect 2 (Pd) withv _Q2=(±2) MHz, ₂=1. Two defects were observed at the In impurities in annealing stage III (around 250 K) after heavy-ion as well as electron irradiations: defect 1(In) withv _Q1=87(±1) MHz, ₁=0 and defect 2(In) withv _Q2=105(±2) MHz, ₂=0.65(±0.02). A third defect (defect 3(In):v _Q3=177(±2) MHz, ₃0.2) appeared above 260 K after heavy-ion irradiation only. The data are interpreted in terms of interstitial trapping at the Pd impurities and vacancy trapping at the In impurities. Information on the microscopic structure of defect 1(In) and 2(In) is obtained from a PAC-single-crystal experiment. For defect 1(In) axial 111-symmetry is found, which leads us to identify this defect with a monovacancy as nearest neighbor with respect to the In probe. Defect 2(In) is the trapped divacancy for which an orientation is found that is consistent with both vacancies being nearest neighbor to the probe but second nearest neighbors to each other.     

Capabilities and Disadvantages of Combined Matrix-Assisted Laser-Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) and High-Performance Thin-Layer Chromatography (HPTLC): Analysis of Egg Yolk Lipids

JPC – Journal of Planar Chromatography – Modern TLC - Lipids are important natural products and essential in nutrition, cosmetic formulations, pharmaceuticals, etc. Lipids and,...     

Simultaneous quantification of propofol,ketamine and rocuronium in just 10 μL plasma using liquid chromatography coupled with quadrupole mass spectrometry and its pilot application to a pharmacokinetic study in rats

The combination of propofol, ketamine and rocuronium can be used for anesthesia of ventilated rats. However, reliable pharmacokinetic models of these drugs have yet to be developed in rats, and consequently optimal infusion strategies are also unknown. Development of pharmacokinetic models requires repeated measurements of drug concentrations. In small animals, samples must be tiny to avoid excessing blood extraction. We therefore developed a drug assay system using high‐performance liquid chromatography coupled with quadrupole mass spectrometry that simultaneously determines the concentration of all three drugs in just 10 μL rat plasma. We established a plasma extraction protocol, using acetonitrile as the precipitating reagent. Calibration curves were linear with R² = 0.99 for each drug. Mean recovery from plasma was 91–93% for propofol, 89–93% for ketamine and 90–92% for rocuronium. The assay proved to be accurate for propofol 4.1–8.3%, ketamine 1.9–7.8% and rocuronium ?3.6–4.7% relative error. The assay was also precise; the intra‐day precisions were propofol 2.0–4.0%, ketamine 2.7–2.9% and rocuronium 2.9–3.3% relative standard deviation. Finally, the method was successfully applied to measurement the three drugs in rat plasma samples. Mean plasma concentrations with standard deviations were propofol 2.0 μg/mL ±0.5%, ketamine 3.9 μg/mL ±1.0% and rocuronium 3.2 μg/mL ±0.8% during ventilation.     

Ueber die Untersuchung von Harzen

Ohne Zusammenfassung     

Novel cyclopentadienyl silanes and disilanes: synthesis, structure and gas-phase pyrolysis

The new chloro(cyclopentadienyl)silanes Cp′SiH_yCl_3−y (Cp′=Me₄EtC₅, y=1: 1; Cp′=Me₄C₅H, y=1: 2; y=0: 3; Cp′=Me₃C₅H₂, y=1: 4 and pentachloro(cyclopentadienyl)disilanes Cp′Si₂Cl₅ (Cp′=Me₅C₅ 5, Me₄EtC₅ 6, Me₄C₅H 7, Me₃C₅H₂ 8, Me₃SiC₅H₄ 9) are synthesized in good yields via metathesis reactions. Treatment of 1–9 with LiAlH₄ leads under Cl–H exchange to the hydridosilyl compounds Cp′SiH₃ (Cp′=Me₄EtC₅ 10, Me₄C₅H 11, Me₃C₅H₂ 12) and to the hydridodisilanyl compounds Cp′Si₂H₅ (Cp′=Me₅C₅ 13, Me₄EtC₅ 14, Me₄C₅H 15, Me₃C₅H₂ 16, Me₃SiC₅H₄ 17). Complexes 1–17 are characterized by ¹H, ¹³C, and ²⁹Si-NMR spectroscopy, IR spectroscopy, mass spectrometry and CH-analysis. The structures of 6, 7 and 9 are determined by single-crystal X-ray diffraction analysis. Pyrolysis studies of the cyclopentadienylsilanes 10–12 and disilanes 13–17 show their suitability as precursors in the MOCVD process.