Spectrophotometric determination of tellurium in trace quantities by use of an ion-association complex.
The formation of an ion-association complex by the interaction of iodotellurate(IV) with cetyltrimethylammonium bromide is used as the basis of an extractive procedure to determine tellurium in the range 2.5-12.5 mug in a final aqueous phase volume of 20 ml. The method is simple, reliable and sensitive. Selectivity is achieved by separation of tellurium on aluminium hydroxide as collector.
The atomic absorption spectroscopy of Tellurium
Abstract Selenium can be determined in aqueous solution by atomic absorption spectroscopy at 1960, 2040,2063 or 2075 A; the sensitivities for these lines with a Techtron 10-cm air-acetylene burner are in the ratio of 1:9:60:93. When a Beckman tripleburner (air-hydrogen) and a triple-pass optical system are used, the most sensitive1960 A line provides a sensitivity of 0.5 p.p.m. and a detection limit of 1.0 p.p.m. The performence in air-hydrogen and air-acetylene flames is described,and optimum experimental conditions determined.With the Se 1960 A line and a Techtron 10-cm air-acetylene burner, selenium extracted into methyl isobutyl ketone as its diethyldithiocarbamate complex gives a sensitivity of 0.30 p.p.m.,which is a 2.4-fold increase over that found in aqueous solution.
Highly enantio- and diastereoselective synthesis of β-methyl-γ-monofluoromethyl-substituted alcohols.
Enanatiopure β-methyl-γ-monofluoromethyl alcohols were prepared from the allylic alkylation between fluorobis(phenylsulfonyl)methane with Morita-Baylis-Hillman carbonates. The reaction was catalyzed by using the Cinchona alkaloid derivative, (DHQD)(2)AQN. The origin of the stereoselectivity was verified by DFT methods. Calculated geometries and relative energies of various transition states strongly support the observed stereoselectivity.