Enige aspecten van de moderne analyse

No abstrac

Möglichkeiten und Grenzen der Identifizierung von Stoffen aus ihrem Verhalten bei der isothermen Eluierungsgaschromatographie

\u3cp\u3eIt is recommended to use partition coefficients for the identification of compounds and to determine these by a simple gas-chromatographic procedure, which allows the control of the measuring conditions. This recommendation combines a relative method of measurement with the determination of absolute quantities. The accuracy of the measurement, which is decisive for the identification, was investigated and it was found that the accuracy in most cases will be limited by the resolving power of the column. For the evaluation of the results obtained with columns with different stationary phases a method was tested in which the partition coefficients measured on two different columns were combined. A table of partition coefficients of 80 hydrocarbons at 50,0° C on squalane and dinonylphthalate as stationary phases was compiled. On the basis of this table the identification of the C\u3csub\u3e5\u3c/sub\u3e-C\u3csub\u3e7\u3c/sub\u3e hydrocarbons in a crack product was carried out.\u3c/p\u3

Qualitative analysis of hydrocarbons by pyrolysis and gas chromatography

\u3cp\u3eA recent paper by Dhont\u3csup\u3e1\u3c/sup\u3e has described the application of pyrolysis to the detection of benzene rings in organic compounds, the pyrolysis products being analysed by gas chromatography. He suggests that the technique may be generally useful for identification of small amounts of material, for example, those separated by gas chromatographic columns.\u3c/p\u3

Highly active and efficient catalysts for alkoxycarbonylation of alkenes

Carbonylation reactions of alkenes constitute the most important industrial processes in homogeneous catalysis. Despite the tremendous progress in this transformation, the development of advanced catalyst systems to improve their activity and widen the range of feedstocks continues to be essential for new practical applications. Herein a palladium catalyst based on 1,2-bis((tert-butyl(pyridin-2-yl)phosphanyl)methyl)benzene L3 (py(t)bpx) is rationally designed and synthesized. Application of this system allows a general alkoxycarbonylation of sterically hindered and demanding olefins including all kinds of tetra-, tri- and 1,1-disubstituted alkenes as well as natural products and pharmaceuticals to the desired esters in excellent yield. Industrially relevant bulk ethylene is functionalized with high activity (TON: >1,425,000; TOF: 44,000 h(−1) for initial 18 h) and selectivity (>99%). Given its generality and efficiency, we expect this catalytic system to immediately impact both the chemical industry and research laboratories by providing a practical synthetic tool for the transformation of nearly any alkene into a versatile ester product