Stirred solutions

C. Palladium on carbon catalyst (5 per cent. Pd). Suspend 41-5 g. of nitric acid - washed activated carbon in 600 ml. of water in a 2-litre beaker and heat to 80°. Add a solution of 4 1 g. of anhydrous palladium chloride (1) in 10 ml. of concentrated hydrochloric acid and 25 ml. of water (prepared as in A), followed by 4 ml. of 37 per cent, formaldehyde solution. Stir the suspension mechanically, render it alkaUne to litmus with 30 per cent, sodium hydroxide solution and continue the stirring for a further 5 minutes. Filter off the catalyst on a Buchner funnel, wash it ten times with 125 ml. portions of water, and dry and store as in B. The yield is 46 g. 

In a 500 ml. bolt-head flask provided with a thermometer (reaching almost to the bottom) and a calcium chloride (or cotton wool) guard tube, place 100 g. of a-bromo-wo-valerj l bromide and 50 g. of dry, finely-divided urea. Start the reaction by warming the flask on a water bath the temperature soon rises to about 80°. Maintain this temperature for about 3 horns the mass will liquefy and then resolidify. Transfer the sticky reaction product to a large beaker containing saturated sodium bicarbonate solution, stir mechanically and add more saturated sodium bicarbonate solution in small quantities until effervescence ceases. Filter at the pump, suck as dry as possible and dry the crude bromural upon filter paper in the air. RecrystaUise the dry product from toluene. Alternatively, recrystaUise the moist product from hot water (ca. 700 ml.). The yield of pure brommal, m.p. 154-155°, is 28 g. 

Add 40 ml. of ethyl alcohol to 21 -5 g. of 70 per cent, ethylenediamine solution (0 -25 mol) dissolve 36 -5 g. of adipic acid (0 -25 mol) in 50 ml. of a 6 1 mixture of ethyl alcohol and water. Mix the two solutions, stir and cool. Filter off the resulting salt and recrystalliae it from 60 ml. of a 6 1 ethyl alcohol - water mixture, and dry the salt in the air. Heat the salt in an atmosphere of oxygen-free nitrogen or of carbon dioxide in an oil bath until it melts (ca. 160°) the product will sohdify after a short time. Reduce the pressure to 15 mm. of mercury or less and raise the temperature of the oil bath until the product remelts (about 290°) and continue the heating for 4r-5 hours. Upon coohng, a nylon type polymer is obtained. 

The next day comes and the hung-over chemist wakens to see a dark red solution stirring away. In some cases where the chemist had made an enormous batch of this stuff, there may be seen a small mass of crystalline precipitate at the bottom of the flask. This is no big deal and will go away in the next step. If the chemist had made this in a flat-bottomed flask (which she really should have for convenience) then the ice tray is removed, the flask returned to the stir plate, a distillation setup attached, and the acetone is vacuum distilled from the flask. After all the acetone has come over the chemist can proceed in two different ways. One way is to just keep on distilling the solution until all of the formic acid has been removed. The chemist knows that just about all the formic has been removed when there is about 300mL of thick black liquid remaining in the reaction flask and hardly any clear formic acid is dripping over into the collection flask. If one were to swirl the reaction flask, the liquid will appear syrupy and kind of coat the sides of the flask. This is more evident when the flask cools. A quick sniff of the flask may indicate that some formic is still in there, but it should be too minimal to be of any concern. 

Do everything else the same except let the solution stir in the O atmosphere for 72 hours. You ll need to check the balloon every 12 hours or so. Replace as needed (when it starts to sag). The... 

Then add a bit of NaHCOs (4 grams) and salt to saturate solution. Stir a bit more. Separate layers, Extract one more time and distill. Time depends on reaction speed. Reaction speed depends on the amount of catalyst and temperature. 60 C seems to be good, more catalyst, less time. More temperature May be more byproducts, this is what happen when acetic acid is the solvent. Probably a good way will be also acetic acid and 40-50 C, but dual phase is easy to extract ans uses less chemicals. 

The flask is placed in a plastic tray because an ice bath may be necessary and stirring is again started. Ice is added as necessary so that the temperature stays below 50°C and the solution stirs... 

To do the reaction the chemist places a flask in an ice bath on top of the stirplate and into it is added lOOmL acetonitrile (CH3CN) and 65g anhydrous mercuric nitrate. A small separatory funnel that has 33g of safrole or 24g allylbenzene is placed over the flask so that everything looks just like that of fig. 9. The safrole is then slowly dripped in so that the temperature stays between 20-28 C. A yellow precipitate will form as the mercuric nitrate latches on to the safrole. After the addition is finished, the ice bath is removed and the solution stirred at room temperature for 1 hour. 

Silver sulfate, Ag2S04—A713 (saturated solution) stir mechanically 10 g of the salt in a liter of water for 3 hours decant and use the clear liquid. 

In order to find optimal conditions for the soluble copper determination we examined the influence of electrolysis potential, electrolysis time, and the solution stirring rate on the accuracy and sensitivity of determination. We found that the optimal parameters for PSA determination of copper were electrolysis potential of -0.9 V vs. 3.5 mol/dm Ag/AgCl, electrolysis time of 300 s, and solution stirring rate of 4000 rpm. The soluble copper content in samples investigated in this study varied from 1.85 to 4.85 ppm. Very good correlation between the copper content determined by PSA and AAS indicated that PSA could be successfully applied for the soluble copper content determination in various dental materials. 

The time necessary for completion of the reaction may vary from 0.5 to 4 hours, depending on the actual activity of the alumina. The progress of conversion should be monitored by infrared analysis of a concentrated sample of the solution. Stirring should be continued for 15 minutes after the nitroso band at 1540 cm. has disappeared. A strong diazo band at about 2100 cm. will then be present. The carbonyl band at 1750 cm. initially due to nitrosocarbamate, will usually not disappear completely during the reaction, because some diethyl carbonate is formed in addition to carbon dioxide and ethanol. Diethyl carbonate is removed during the work-up procedure. 

Reduction of 6p, 9-Oxidoprogesterone to 9-Hydroxyprogesterone. Zinc powder Note 2) (4. g) is added in small portions to a solution of 2 g of 6)5,19-oxidoprogesterone in 40 ml glacial acetic acid Note i). The mixture is stirred for 40 min, then an additional 4 g zinc is added and stirring is continued for another 40 min at 30°. The cooled solution is filtered, the inorganic residue washed with methanol and the filtrate evaporated under reduced pressure. The resultant crude product is dissolved in 60 ml of chloroform and filtered. Concentrated hydrochloric acid (0.6 ml) is added and the solution stirred for 10 min at 25°. The reaction mixture is diluted with ether, washed successively with water, sodium bicarbonate solution and again with water, dried and evaporated under reduced pressure. The... 

The next step yields 1-(3-acetylthio-2-methylpropanoyl)-L-proline tert-butyl ester. L-proline tert-butyl ester (5.1 g) is dissolved in dichloromethane (40 ml) and the solution stirred and chilled in an ice bath. Dicyclohexylcarbodiimide (15 ml) is added followed immediately by a solution of 3-acetylthio-2-methylpropanoic acid (4.9 g) in dichloromethane (5 ml). After 15 minutes stirring in the ice bath and 16 hours at room temperature, the precipitate is filtered off and the filtrate is concentrated to dryness in vacuo. The residue is dissolved in ethyl acetate and washed neutral. The organic phase is dried over magnesium suifateand concentrated to dryness in vacuo. The residue 1-(3-acetylthio-2-methylpropanoyl)-L-proline tert-butyl ester is purified by column chromatography (silica gel-chloroform), yield 7.9 g. 

Synthesis of 16,16-dimethyl-trans-A -PGEi 2.35 g of the bis-tetrahydropyranyl ether were dissolved in 6 ml of tetrahydrofuran and 60 ml of 65%-acetic acid aqueous solution and the solution stirred at 60°C to 70°C for 20 minutes. The reaction mixture was extracted with ethyl acetate, and the organic layer was washed with water, dried and concentrated under reduced pressure. The residue was purified by column chromatography on silica gel using ethyl acetate-cyclohexane (2 3) as eluent to yield 270 mg of the title compound. 

A solution of sodium borohydride (8 grams) in water (16 ml) was added to a stirred solution of 2(3,16(3-bis-piperidino-5a-androstan-3a-ol-17-one (17 grams) in tetrahydrofuran (70 ml) and methanol (30 ml) and the solution stirred at room temperature for 16 hours. The product was precipitated by the addition of water, filtered off, dried, and crystallized from acetone to give the diol (14.9 grams). 

N-methyl-1 -(methylthio)-2-nitroetheneamine (230 g) in water (400 ml) was stirred and heated at 45°C to OO t. 2-[ [ [5-(Dimethylamino)methyl-2-furanyl] methyl] thiol ethanamine (321 g) was added dropwise over 4 hours and the resultant solution stirred for a further 3 A hours. 

Forced convection can be achieved in a variety of ways, e.g. by agitating the solution (stirring mechanically, sparging with gas bubbles, ultrasonic radiation, etc.) or by moving or rotating the metal electrode, and this will result in more rapid transport of the reacting species to the electrode than when the solution is unagitated. 

Procedure. Weigh out accurately about 2.5 g of finely powdered mercury(II) chloride, and dissolve it in 100 mL of water in a graduated flask. Shake well. Transfer 25.0 mL of the solution to a conical flask, add 25 mL water, 2mL 1M hydrochloric acid, and excess of 50 per cent phosphorous(III) acid solution. Stir thoroughly and allow to stand for 12 hours or more. Filter the precipitated mercury(I) chloride through a quantitative filter paper and wash the precipitate moderately with cold water. Transfer the precipitate with the filter paper quantitatively to a 250 mL reagent bottle, add 30 mL concentrated hydrochloric acid, 20 mL water, and 5 mL carbon tetrachloride or chloroform. Titrate the mixture with standard 0.025M potassium iodate in the usual manner (Section 11.127). 

A solution of a 4-azidoquinoline (0.5-0.6 g) and NaOMe (0.3 0.35 g, large excess) in a mixture of MeOH (75 mL) and dioxane (75 mL) was irradiated for 20-30 min with a 400-W high-pressure Hg lamp under N2. A further quantity of NaOMe (1.0-2.0 g) was added and the solution stirred at 20 C for 7-8 h and then concentrated in vacuo. The residue was treated with ice-water (30 mL) and the mixture was extracted with Et20. The extract was washed with sat. brine, dried and evaporated under reduced pressure. The residue was chromatographed (silica gel, Et20) to give the 3//-1,4-benzodiazepine as a yellow oil. 

The drop in current that occurs in coulometric experiments may arise not only from the decrease in bulk concentration of the substance being analyzed, but also from a decrease in its surface concentration caused by the development of concentration gradients (see Section 11.2.1). Low values of current density and strong solution stirring are used to avoid the interference of such effects. Thin-layer cells where the electrodes are very close together (tens of micrometers) and the parameter ratio SIV is high, are often used to shorten the experiments. 

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