Nitrogen atmospheric concentration

To achieve the very low initial fluorine concentration in the LaMar fluorination process initially a helium or nitrogen atmosphere is used in the reactor and fluorine is bled slowly into the system. If pure fluorine is used as the incoming gas, a concentration of fluorine may be approached asymptotically over any time period (Fig. 3). It is possible to approach asymptotically any fluorine partial pressure in this manner. The very low initial concentrations of fluorine in the system greatiy decreases the probabiUty of simultaneous fluorine coUisions on the same molecules or on adjacent reaction sites. 

The above nitrite (0.93 g) is dissolved in 40 ml of dry benzene and irradiated for 1 hr at 0-5° in a nitrogen atmosphere with two 200 Watt mercury lamps. The resulting suspension is concentrated and filtered to give 0.59 g of essentially pure 20a-hydroxy-18-oximinopregn-4-en-3-one as a benzene solvate mp 110-125°. Recrystallization from acetone gives an analytical sample mp 184-186° [a] 149° (CHCI3). 

The reaction is carried out in a manner similar to that described above (Chapter 11, Section II). In a 250-ml flask fitted with stirrer, condenser, and dropping funnel is placed a solution of 19.25 g (0.0505 mole) of the phosphonium salt in 180 ml of THF. The nitrogen atmosphere is established and 0.05 mole of phenyllithium added (as a solution in benzene, available from Foote Mineral Co.). The mixture is stirred for 45 minutes at room temperature and then refluxed for 15 minutes. To the red-brown solution is added dropwise over 20 minutes 4.91 g (0.05 mole) of distilled cyclohexanone stirring is continued for 24 hours. The mixture is then concentrated by distillation at... 

A 250-ml three-necked flask is fitted with a condenser (drying tube). The system is flushed with dry nitrogen, and a dry nitrogen atmosphere is maintained. In the flask is placed a solution of potassium /-butoxide (2.8 g, 0.025 mole) in dry /-butyl alcohol (100 ml). 4-Benzoyloxycyclohexanone (5 g, 0.022 mole, Chapter 7, Section X) is added to the solution, the transfer being assisted by the use of 10-15 ml of dry /-butyl alcohol. The mixture is cautiously brought to reflux, and refluxing is continued for 45 minutes. The mixture is then cooled rapidly to room temperature and carefully acidified by the addition of 10 ml of 6 A hydrochloric acid (potassium chloride will precipitate). The mixture is placed on a rotary evaporator and the bulk of the solvent is removed. The residue is diluted with sufficient water to dissolve the potassium chloride and extracted three times with 50-ml portions of ether. The ether extracts are combined and extracted four times with 100-ml portions of aqueous 5% sodium bicarbonate solution. The bicarbonate extracts are combined and the solution is acidified by the addition of concentrated hydrochloric acid to pH 4. The mixture is now extracted three times with 100-ml portions of ether, the combined ethereal extracts are washed with water, then dried, and the solvent is removed. The residual product may be recrystallized from benzene-hexane. The acid has mp 65-68°. 

There were placed 120 g of Lthree-necked flask equipped with a stirrer thermometer and methanol/dry ice cooling and 1.5 liters of liquid ammonia were allowed to enter at -40°C. Then there were added under continuous cooling 50 g (2.17 mols) of sodium metal in portions of 1 to 2 g during the course of one hour. The end of the reaction was recognized by the continuation of the blue color. After the end of the reaction the excess sodium was destroyed by the addition of ammonium chloride and the ammonia vaporized at normal pressure. The residue was taken up in 500 ml of water and concentrated in a vacuum to 200 ml in order to remove residual ammonia, and again treated with 300 ml of water. The entire operations were carried out under a nitrogen atmosphere. 

A mixture consisting of 22.7 g potassium o-bromobenzoate, 16.6 g 2,6-dichloro-3-methvlani-line, 12 ml N-ethylmorpholine, 60 ml diethylene glycol dimethyl ether, and 1.0 g anhydrous cupric bromide is heated in a nitrogen atmosphere at 145 C to 155°C for 2 hours. The reaction mixture is diluted with 60 ml diethylene glycol dimethyl ether and acidified with 25 ml concentrated hydrochloric acid. The acidic mixture is diluted with 100 ml of water and the liquid phase decanted from the insoluble oil. The insoluble oil is stirred with methanol and the crystalline N-(2,6-dichloro-3-methylphenyl)anthranilic acid which separates is collected and washed with methanol. The product, after recrystallization from acetone-water mixture melts at 248 C to 250°C. 

Bj Preparation of 11 ji-Methoxy-A ° -Estratriene-3-ol-17-one 12.3 g of 11/3-methoxy-A -estradiene-3,17-dione were dissolved in 1,230 cc of methanol and then, under an atmosphere of nitrogen, 7.38 g of palladium hydroxide were added and the mixture was held at reflux for one hour under agitation and a nitrogen atmosphere. Then the reaction mixture was cooled to 30°C, filtered, vacuum filtered and washed with methanol. The metha-nolic solutions were concentrated to about 50 cc, allowed to stand overnight at room temperature and filtered. The precipitate formed was triturated in methanol and dried at 80°C to obtain 10.74 g (yield = 87.5%) of 11/3-methoxy-A " -estratriene-3-ol-17-one having a MP of 264°C. 

In order to prepare the monoacetate, the crude diacetate is suspended in 150 cc of methanol and, after adding 1.5 cc, concentrated hydrochloric acid, heated to boiling for 15 minutes in a nitrogen atmosphere. The crude monoacetate mhich separates upon the addition of meter after cooling is filtered off, meshed end dried in vacuo over calcium chloride at room temperature. The pure 17-ecetete, obtained after repeated recrystellizetions from methylene chloride/hexane has a MP of 161° to 162°C. 

In another representative procedure about 2.3 mols of 2,6-di-tert-butyl-4-mercaptophenol is dissolved in about 1,700 ml of methanol under a nitrogen atmosphere about 100 ml of concentrated hydrochloric acid and 1B0 ml of acetone are added, and the mixture is stirred and maintainedat a temperature of about 35°C to 50°C, for 1.5 hours. The mixture is then cooled to room temperature and filtered, and the bis(3,5-di-tert-butyl-4-hydroxyphenyl) acetone mercaptole product is collected as a colorless crystalline solid filter cake. The product is washed with water and aqueous sodium bicarbonate and purified by recrystallization from ethanol. 

The reduction of atmospheric concentrations of the sulfur and nitrogen oxides blamed for acid rain was a major issue in the debate that led to the 1990 Clean Ail-Act Amendments (CAAA). The final legislative action is one of the most complex and comprehensive pieces of environmental legislation ever written. 

A mixture of 1.4 g (10 mmol) of 4-chlorobenzaldehyde and 0.71 g (5 mol %) of the chiral polymer E is stirred in 10 mL of dry toluene for 15 h, under a dry nitrogen atmosphere, to form the Schiff base. After cooling to 0lC, 15 mL (15 mmol) of 1 M diethyl/inc in hexane is added and the mixture is stirred for a further 24 h at O C. 1 N HC1 is then added dropwise at O C, and the chiral polymer is removed by filtration. The polymer is washed several times with 11,0 and Et,0. The aqueous layer is separated and extracted with Et20. The combined organic layer is dried over MgS04 and concentrated under reduced pressure. The crude product is purified by column chromatography (silica gel, CHC1,) yield 1.61 g (95 %) 99 % ee [a]2,0 —23.9 (r = 4.93, benzene). 

Since high temperatures and a nitrogen atmosphere are necessary to obtain measurable rates of polyesterification and to remove the reaction water, a loss of volatile reactants can hardly be avoided, especially in early stages of polyesterification. In the last stages, the decrease of the concentration of the volatile reactants can be of the same order of magnitude as their concentration. Consequently, the ultimate points of the kinetic plot have possibly no significance. 

Because of their resistance to chemicai attack, nitrogen atoms are not iocked up in solid or liquid substances as are other eiements such as Si, Ai, Fe, and H. The most stabie form of the eiement nitrogen is a gaseous diatomic moiecuie with a very strong tripie bond. Therefore, the eiement nitrogen is concentrated in the Earth s gaseous atmosphere even though it is oniy a trace eiement in overaii abundance. 

An aqueous solution with an appropriate concentration of the nanocrystals was spin-coated onto PMMA-coated clean coverglasses. The samples were measured under nitrogen atmosphere at room temperature. 

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