Cooling transfer

Pure dimethylaniline from commercial dimethylaniline. Into a 250 ml. round-bottomed flask fitted with a reflux condenser place 50 g. (52-5 ml.) of a good commercial sample of dimethylaniline and 25 g. (23 ml.) of acetic anhydride. Heat vmder reflux for 3 hours, and allow to cool. Transfer to a 100 ml, Claisen flask equipped for distillation, and distil using a wire gauze or, better, an air bath (Fig. II, 5, 3). Some acetic acid and the excess of acetic anhydride passes over first, followed by pure dimethylaniline (a colourless liquid) at 193-194°, There is a small dark residue in the flask. The yield depends upon the purity of the commercial sample, but is usually 30-40 g. 

Triturate 20 g. of dry o-toluidine hydrochloride and 35 5 g. of powdered iodine in a mortar and then grind in 17 -5 g. of precipitated calcium carbonate. Transfer the mixture to a conical flask, and add 100 ml. of distilled water with vigorous shaking of the flask. Allow the mixture to stand for 45 minutes with occasional agitation, then heat gradually to 60-70° for 5 minutes, and cool. Transfer the contents of the flask to a separatory funnel, extract the base with three 80 ml. portions of ether, diy the extract with anhydrous calcium chloride or magnesium sulphate, and remove the excess of solvent. The crude 5-iodo-2-aminotoluene separates in dark crystals. The yield is 32 g. Recrystallise from 50 per cent, alcohol nearly white crystals, m.p. 87°, are obtained. 

Rapidly add 2.0 g of zinc to the vessel A, immediately insert the stopper, and allow the gases to bubble through the solution for 30 minutes. At the end of this time the solution in D should still contain some iodine. Disconnect the delivery tube C and leave it in the absorption tube. Add 5.0 mL of the ammonium molybdate-hydrazine reagent and a drop or two of sodium disulphite solution. Heat the resulting colourless solution in a water bath at 95-100 °C, cool, transfer to a lOmL graduated flask, and make up to volume with water. 

Procedure. Dissolve a suitable weight of the sample of lead in 6M nitric acid add a little 50 per cent aqueous tartaric acid to clear the solution if antimony or tin is present. Cool, transfer to a separatory funnel, and dilute to about 25 mL. Add concentrated ammonia solution to the point where the slight precipitate will no longer dissolve on shaking, then adjust the pH to 1, using nitric acid or ammonia solution. Add 1 mL freshly prepared 1 per cent cupferron solution, mix, and extract with 5 mL chloroform. Separate the chloroform layer, and repeat the extraction twice with 1 mL portions of cupferron solution + 5 mL of chloroform. Wash the combined chloroform extracts with 5mL of water. Extract the bismuth from the chloroform by shaking with two 10 mL portions of 1M sulphuric acid. Run the sulphuric acid solution into a 25 mL graduated flask. Add 3 drops saturated sulphur dioxide solution and 4 mL of 20 per cent aqueous potassium iodide. Dilute to volume and measure the transmission at 460 nm. 

Pipette a 25 mL or 50 mL aliquot of the clear sample solution into a 250 mL conical flask, add 5 mL concentrated sulphuric acid, 5 mL 85 per cent phosphoric(V) acid, and 1-2 mL of 0.1 M silver nitrate solution, and dilute to about 80 mL. Add 5 g potassium persulphate, swirl the contents of the flask until most of the salt has dissolved, and heat to boiling. Keep at the boiling point for 5-7 minutes. Cool slightly, and add 0.5 g pure potassium periodate. Again heat to boiling and maintain at the boiling point for about 5 minutes. Cool, transfer to a lOOmL graduated flask, and measure the absorbances at 440 nm and 545 nm in 1 cm cells. 

The cooling bath is then replaced by a steam bath, and the reaction mixture is refluxed for 16 hours. It is then cooled, transferred to a one-necked, 1-1., round-bottomed flask, and concentrated to dryness on a rotary evaporator. The dark residue is dissolved in a mixture of 200 ml. of water, 200 ml. of dichloromethane, and 20 ml. of triethylamine, and the aqueous phase is separated and washed with two 200-ml. portions of dichloromethane. The organic phases are combined and washed with 300 ml. of saturated aqueous sodium chloride, dried over anhydrous magnesium sulfate, and filtered. Removal of the solvent on a rotary evaporator gives a red oil, which solidifies on storage at 0-5° (Note 5). Recrystallization of this solid from 40 ml. of absolute ethanol gives 7.6-8.4 g. (34-37%) of ethyl 4-amino-3-(methylthiomethyl)-benzoate, m.p. 83-85°. A second crop of l.l-2.5g. of crystalline material, m.p. 78-83°, may be obtained by concentration of the mother liquors (Note 6). 

Thionyl chloride method. Mix 100 g. of pure p-nitrobenzoic acid and 126 g. (77 ml.) (1) of redistilled thionyl chloride in a 500 ml. round-bottomed flask. Fit the flask with a double surface reflux condenser carrying a calcium chloride (or cottou wool) guard tube and connect the latter to an absorption device e.g., Fig. II, 8, 1. c). Heat the flask on a water bath with occasional shaking for 1 hour or until the evolution of hydrogen chloride and sulphur dioxide ahnost ceases. Allow the reaction mixture to cool, transfer it cautiously to a Claisen flask connected with a water-cooled condenser and a receiver (compare Fig. II, 13, 1). Distil off the excess of thionyl chloride (b.p. 77°) slowly and continue the distillation until the temperature rises rapidly to about 120° this will ensure that all the thionyl chloride is remov. Allow to cool, and distil the residual p-nitrobenzoyl chloride under diminished pressure as detailed in the Phosphorus Pentachloride Method. The resulting p-nitrobenzoyl chloride (a yellow crystalline solid) weighs 107 g. and melts at 72-73°. 

Heat and reflux a 5-g portion of soil sample with 50 mL of methanol-phosphate buffer (pH 7)-water (15 7 28, v/v/v) solvent mixture in a round-bottom flask for 1 h. After cooling, transfer a 10-mL portion of the supernatant to a test-tube and mix with 11 mL of 0.02M H3PO4 solution. Load this solution on to a silica-based SPE cartridge (Analytichem International Clin-Elut 1020) at a flow rate of 1-2 drops per second. Discard this fraction. Elute the analytes with 30 mL of dichloromethane. Concentrate the eluate to dryness with air in a water-bath at a temperature of 40 °C (do not use vacuum). Dissolve the residues in 5mL of HPLC injection solution [900 mL of water - - 50 mL of phosphate buffer (pH 7) 4-50 mL of ACN 4-4 g of TBABr]. Pinal analysis is performed using liquid chromatography/ultraviolet detection (LC/UV) with a three-column switching system. 

Heat the flask gently until frothing ceases, more strongly until the solution clears, and then for a further 1 h with the sulphuric acid condensing in the lower part of the neck of the flask. Allow to cool, carefully add approximately 100 ml of water and warm to dissolve the soluble material. When cool, transfer quantitatively into a 250-ml volumetric flask and dilute to 250 ml. Retain the diluted digest for the determination of ammonium nitrogen. 

In a 500-mI. flask equipped with a reflux condenser are placed 48.4 g. (0.20 mole) of a-phenyl-a-carbethoxyglutaronitrile/ 225 ml. of hydrochloric acid (sp. gr. 1.19), and 50 ml. of acetic acid. The mixture is heated under reflux for 10 hours. The solution is cooled, transferred to a 1-1. separatory funnel, and diluted with 300 ml. of water. The a-phenylglutaric acid is extracted with five 100-ml. portions of ether-ethyl acetate (1 1) (Note 1). The extracts are combined, washed once with saturated sodium chloride solution, and dried over anhydrous magnesium sulfate. The solvents are removed as completely as possible by distillation from a steam bath, and the residue is transferred to a 200-ml. flask. Acetic anhydride (50 ml.) is added, and the solution is heated under gentle reflux for 1 hour. The excess acetic anhydride is removed by distillation at atmospheric pressure, and the residue is distilled under reduced pressure through a short (15-cm.) Vigreux column with an air-cooled side arm. The product is collected at 178-188°/0.5-l mm. (Note 2). The yield is 31.1-32.7 g. (82-86%) m.p. 90-94°. 

Solubiliiy in Nitric Acid. Add an 80 g sample with stirring to 100 g of 97.5 to 99-0% nitric acid in a 200 ml beaker. After allowing the soln to cool, transfer a 100 ml portion to a 100 ml Goetz (or equal) oil sedimentation tube and centrifuge at 1800 rpm for 20 mins, using an 8-in centrifuge head. 

To prepare the solution measure out 333 ml of I 8 0 M H2SO., ancj dilute >3 to 2 00 liters in a volumetric flask Shake well for uniformity Because the interaction of concentrated H2S04 with HzO evojves mm h j,eat ancj can cause hazardous splattering, it is better to do a partial dilution with about one liter of water first in a beaker Then, after cooling, transfer the contents to the volumetric flask, and complete the dilution The final dilution to the mark must be made with the solution at room temperature... 

Method II.—10 gms. of p-nitrotoluene and a crystal of iodine dissolved in 100 c.cs. of carbon tetrachloride are placed in a silica flask provided with a reflux condenser. The solution is covered with water (about 50 c.cs.) and heated to gentle boiling, while situated about 15 cms. from a mercury vapour lamp (Fig. 46). A solution of 15 gms. bromine in 50 c.cs. carbon tetrachloride is then run in drop by drop from a dropping funnel at the top of the condenser. When all the bromine is in, boiling is continued until the solution becomes almost colourless. The contents of the flask are cooled, transferred to a separating funnel, and the lower carbon tetrachloride layer run into a distilling flask. Carbon tetrachloride is distilled off over a water bath, and the residue of p-nitrobenzyl bromide recrystallised from alcohol or petroleum ether. 

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