Temperature solvent system evaporation

B. 2,2-(Trimethylenedithio)cyclohexanone. A solution of 3.02 g. (0.02 mole) of freshly distilled 1-pyrrolidinocyclohexene, 8.32 g. (0.02 mole) of trimethylene dithiotosylate4 (Note 2), and 5 ml. of triethylamine (Note 3) in 40 ml. of anhydrous acetonitrile (Note 4), is refluxed for 12 hours in a 100-ml., round-bottom flask under a nitrogen atmosphere. The solvent is removed under reduced pressure on a rotary evaporator, and the residue is treated with 100 ml. of aqueous 0.1 N hydrochloric acid for 30 minutes at 50° (Note 5). The mixture is cooled to ambient temperature and extracted with three 50-ml. portions of ether. The combined ether extracts are washed with aqueous 10% potassium bicarbonate solution (Note 6) until the aqueous layer remains basic to litmus, and then with saturated sodium chloride solution. The ethereal solution is dried over anhydrous sodium sulfate, filtered, and concentrated on a rotary evaporator. The resulting oily residue is diluted with 1 ml. of benzene and then with 3 ml. of cyclohexane. The solution is poured into a chromatographic column (13 x 2.5 cm.), prepared with 50 g. of alumina (Note 7) and a 3 1 mixture of cyclohexane and benzene. With this solvent system, the desired product moves with the solvent front, and the first 250 ml. of eluent contains 95% of the total product. Elution with a further 175 ml. of solvent removes the remainder. The combined fractions are evaporated, and the pale yellow, oily residue crystallizes readily on standing. Recrystallization of this material from pentane gives 1.82 g. of white crystalline 2,2-(trimethylenedithio)cyclo-hexanone, m.p. 52-55° (45% yield) (Note 8). 

It is important for all sample custodians to maintain the sample in its original physical and chemical condition so that it remains representative of the bulk system in terms of the analyte identity and concentration. Possible changes to avoid are 1) loss of sample matrix or solvent through evaporation or other means, 2) loss of analyte through evaporation, chemical reaction, temperature effects, bacterial... 

Aromatic aldehydes (10 mmol) and trimethylorthoformate (20 mmol) was added to a mixture of sulfonamide (10 mmol), finely powdered calcium carbonate (9 g) and K-10 clay (2 g). The solid homogenized mixture was placed in a modified reaction tube which was connected to a removable cold finger and sample collector to trap the ensuing methanol and methyl formate. The reaction tube is inserted into Maxidigest MX 350 (Prolabo) microwave reactor equipped with a rotational mixing system. After irradiation for a specified period, the contents were cooled to room temperature and mixed thoroughly with ethyl acetate (2 x 20 mL). The solid inorganic material was filtered off and solvent was evaporated to afford tlie residue which was crystallized from the mixture of hexane and ethyl acetate. 

Method. The amino acid derivatives are prepared by adding disyl chloride (1 mg/ml in acetone) to an equal volume of a solution of the amino acid (ca. 5 10 4 jumoles/ml in 0.1 M sodium bicarbonate solution). The reaction is allowed to proceed for 3 h at room temperature. The solvent is evaporated and the residue is dissolved in 1 ml of acetone-methanol (1 1) for application to a thin-layer plate of silica gel. A number of solvent systems used for the separation of amino acid derivatives is given in Table 4.14. After chromatography, the plates are dried at 10S °C for S min, cooled to room temperature and dipped in a solution of sodium ethoxide (S g of sodium per 100 ml of 96% ethanol). The plate is observed immediately under UV light at 365 nm. The amino acid derivatives appear yellow-green. 

This adhesive is a resin/solvent adhesive material compounded to supply satisfactory initial tack. The solvent system has been carefully selected for somewhat rapid evaporation, thereby requiring minimum temperature and ventilation. Useful in textiles and paper board industries. 

A mixture of 7.8 g. (0.062 gram atom) of iodine and 1 g. of red phosphorus is put in a flask equipped with an air condenser on which is placed a calcium chloride tube to protect the system from atmospheric moisture. The flask is heated in an oil or metal bath to a temperature of 100°, and 15.6 g. (0.058 mole) of n-octadecyl alcohol is added. The bath temperature is then raised to 180° and held there for 1 hour. The cooled reaction mixture is extracted with petroleum ether (b.p. 70-80°), and the resulting solution is boiled with fuller s earth and filtered. The solvent is evaporated from the filtrate, giving 21.5 g. (97.5%) of n-octadecyl iodide melting at 34.5-35°. 

Redox processes involving 178 have also been studied.Anodic oxidation of thianthrene has been eifected in a wide variety of solvents. Use of trifluoracetic acid gives stable solutions of 178 and, if perchloric acid is included, the solid perchlorate salt may be isolated on evaporation of the solvent after electrolysis. Dichloromethane at low temperatures has been used and, at the opposite extreme, fused aluminum chloride-sodium chloride mixtures. " Propylene carbonate permits the ready formation of 178, whereas the inclusion of water in solvent mixtures gives an electrochemical means of sulfoxidizing thianthrene. Reversible oxidation of 178 to thianthrenium dication may be brought about in customary solvents such as nitriles, nitro compounds, and dichloromethane if the solvent is treated with neutral alumina immediately before voltammetry addition of trifluoracetic anhydride to trifluoracetic acid equally ensures a water-free medium. The availability of anhydrous solvent systems which permit the reversible oxidation and reduction of 178 has enabled the determination of the equilibrium constants for the disproportionation of the radical and for its equilibria with other aromatic materials. ... 

Vapour pressure of solutions. The Clausius equation can be applied directly to the evaporation of a solution if we make the restriction that the concentration of the solution shall not alter appreciably when 1 mol. of the solvent is evaporated, which is the case if we are dealing with a very large volume of the solution. The system solution-vapour is then monovariant, and has a definite vapour pressure p at every temperature. If the dissolved substance (solute) has no appreciable vapour pressure, this pressure p is equal to the partial pressure of the solvent. If not, the vapour pressure is equal to the total pressure, i.e. to the sum of the partial pressures of all the components of the solution. In the meantime we shall restrict ourselves to the first case. 

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