Thin-layer chromatography temperature control

Substituted adducts similar to 50 have been obtained from the reactions carried out in chlorobenzene and in toluene 19>. Whereas methanesulphonyl azide does not thermolyze appreciably below 120 °C, when a solution of CH3SO2N3 in benzene was heated at 80 °C for 100 hr, 47 (ca. 0.5%) could be detected by thin layer chromatography but no 49 38>. Almost all the azide remained undecomposed. Similarly, very small, amounts of 47 were observed, together with much tar and undecomposed azide, on photolysis of CH3SO2N3 in benzene at room temperature or at 80 °C 10). This confirms that azepine formation is the kinetically controlled process, while the anilides are the products of thermodynamic control. 

Argentation thin-layer chromatography is an extemely useful procedure for the separation of methyl esters of fatty acids. Saturated fatty acids have the highest Rf values, which decrease with the increasing degree of unsaturation, and for a particular acid, the trans isomer usually travels ahead of its corresponding cis isomer. The solvents most commonly used contain hexane and diethyl ether (9 1) although a mixture of 4 6 is used to separate compounds with more than two double bonds. In order to separate positional isomers of the same acid, conditions must be carefully controlled and multiple development in toluene at low temperatures is often necessary. 

Different sizes of films were formed. The samples were cut to measure film properties and to establish a film thickness control equation. The small-diameter films were used for the water vapor permeability (WVP) and puncture strength (PS) large ones for tensile strength and elongation at break (%) measurement. The volume of solution was added over PVC plates at volume constant using a thin layer chromatography spreader. The plates were placed on a leveled surface to achieve uniform films and dried at room condition (25 2°C and 58 3% HR) for 24 to 48 h. Films used for each property measurement were manufactured and stored under the same temperature but at different relative humidity conditions. 

The IR-spectra of 41 tobacco alkaloids and related compounds have been tabulated (S5). Nornicotine, nicotine, myosmine, nicotyrine, anabasine, anatabine, and dihydronicotyrine were separated from an extract of tobacco alkaloids by countercurrent partition (86). Thin-layer chromatography has been used to separate nicotine, nornicotine, anabasine, and nicotyrine (57). The use of gas chromatography to separate tobacco alkaloids has been studied. The retention times of 11 tobacco alkaloids on polyethylene glycol columns has been reported (88) and the effect of the column packing on the retention times of pyridine bases has been described (89). Mixtures containing pyrrolidine, piperidine, pyridine, and various alkylated pyridines have been separated using programed temperature control (90). 

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