Capillary gas chromatography of C1−C4 alkyl tert-butyl ethers

Summary The separation of C₁–C₄ alkyl tert-butyl ethers with the general formula (CH₃)₃C–O–R (R-alkyl substituent) on fused-silica capillary columns coated with dimethylsilicone and cyanopropylmethylsilicone stationary phases was investigated. Retention indices were determined at two temperatures in order to understand their chromatographic behaviour. The respective standard deviations were 0.3 and 0.5 i.u.     

Gas chromatographic retention indices for alkenes on OV-101 and squalane capillary columns

Summary Gas chromatographic retention indices for 47 C₅ to C₈ alkenes on OV-101 dimethylsilicone at 50 and 70 °C were determined within a standard deviation of 0.3i.u. Data obtained on OV-101 are compared with those measured on squalane. The comparison of the retention index and dl/dT values from both columns is presented as linear regression equations with correlation coefficients greater than 0.98.     

Gas chromatographic analysis of C1–C4 nitroparaffins. Separation and identification

Summary The separation of C₁–C₄ nitroparaffins on SE-30, PEGA and Porapak R stationary phases was investigated. The nitroparaffin mixture was obtained from a real technological process. The best separation was achieved on Porapak R at 190°C. The fact that each peak obtained from this column corresponded to a single compound was checked by utilizing the linear relationship between the peak widths and the adjusted retention times (t _R ). Peak identification was carried out using the chromatographic data only, with help of plots of log t _R vs. carbon number and log t _R vs. boiling point; some of the results were also confirmed with comparing the retention times with those of pure substances and IR investigation of the collected chromatographic fraction.     

Retention indices of alkenes and the corresponding epoxides on a capillary column coated with cyanopropyl methyl silicone phase

Summary Retention indices or five 1-alkenes, seven branched alkenes and five cycloalkenes and the corresponding epoxides were determined at two temperatures on a fused-silica capillary column coated with cyanopropyl methyl siloxane to interpret their chromatographic behaviour. The standard deviation was 0.2 index units.     

Capillary gas chromatography of hydrogenation products of 1,5,9-cyclododecatriene stereoisomers

Summary The separation of the products obtained by the hydrogenation of 1,5,9-cyclododecatriene stereoisomers on fused-silica capillary columns coated with dimethylsilicone and cyanopropylmethylsilicone stationary phases was investigated. Retention indices of cyclododecatrienes, cyclododecadienes, cyclododecenes and cyclododecane were determined at three temperatures. The respective standard deviations were 0.3 and 0.6 i.u. The influence of the polarity of the stationary phases on the chromatographic retention of these cyclic hydrocarbones is discussed.     

Glass capillary gas chromatography of C1−C4 mononitroalkanes. Pre-calculation of the relative retention

Summary The separation of C₁–C₄ mononitroalkanes on four wall-coated glass open tubular (capillary) columns (liquid phases: OV-101, Ucon-LB-550X, NPGS and Carbowax 20M) was investigated. Retention indices were determined and the influence of the different factors (analysis temperature, method of determining the gas holdup time and the nature of the stationary phases) on their reproducibility were studied. Linear regression equations permit the pre-calculation of the retention indices of C₁–C₄ mononitroalkanes from their properties on all liquid phases studied.     

Effect of electric-field-induced capillary attraction on the motion of particles at an oil-water interface

Here, we investigate experimentally and theoretically the motion of spherical glass particles of radii 240-310 microm attached to a tetradecane-water interface. Pairs of particles, which are moving toward each other under the action of lateral capillary force, are observed by optical microscopy. The purpose is to check whether the particle electric charges influence the particle motion, and whether an electric-field-induced capillary attraction could be detected. The particles have been hydrophobized by using two different procedures, which allow one to prepare charged and uncharged particles. To quantify the hydrodynamic viscous effects, we developed a semiempirical quantitative approach, whose validity was verified by control experiments with uncharged particles. An appropriate trajectory function was defined, which should increase linearly with time if the particle motion is driven solely by the gravity-induced capillary force. The analysis of the experimental results evidences for the existence of an additional attraction between two like-charged particles at the oil-water interface. This attraction exceeds the direct electrostatic repulsion between the two particles and leads to a noticeable acceleration of their motion.     

Intensities of two-quanta cascades at different excitation energies of compound nuclei146Nd,174Yb and183W

Intensities of two-quanta cascades are obtained (measured) for 2–3 final low-lying levels of the following nuclei¹⁴⁶Nd,¹⁷⁴Yb and¹⁸³W. These measured intensities are compared with the intensities calculated in the frame of various models at primary transition energies ranging from about 0.5 MeV to the neutron binding energy. Some excitation energy intervals are revealed, experimentally obtained intensities of cascade are inconsistent with model calculations.     

Use of Stang's reagent, PhI(CN)OTf, to promote Pummerer-like oxidative cyclization of 2-(phenylthio)indoles

Treatment of various 2-(phenylthio)indoles, bearing nucleophilic groups tethered to C(3), with PhI(CN)OTf initiated an oxidative cyclization sequence that afforded 3,3-spirocyclic 2-(phenylthio)indolenines or oxindoles in moderate yield.