Atmosphere free oxygen

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. 

Graphite is chosen for use in nuclear reactors because it is the most readily available material with good moderating properties and a low neutron capture cross section. Other features that make its use widespread are its low cost, stabiHty at elevated temperatures in atmospheres free of oxygen and water vapor, good heat transfer characteristics, good mechanical and stmctural properties, and exceUent machinabUity. 

There are two ways to produce acetaldehyde from ethanol oxidation and dehydrogenation. Oxidation of ethanol to acetaldehyde is carried out ia the vapor phase over a silver or copper catalyst (305). Conversion is slightly over 80% per pass at reaction temperatures of 450—500°C with air as an oxidant. Chloroplatinic acid selectively cataly2es the Uquid-phase oxidation of ethanol to acetaldehyde giving yields exceeding 95%. The reaction takes place ia the absence of free oxygen at 80°C and at atmospheric pressure (306). The kinetics of the vapor and Uquid-phase oxidation of ethanol have been described ia the Uterature (307,308). 

Deaerated water is prepared as follows. A boiling stone is added to distilled water which is then boiled under reflux for at least 5 minutes it is cooled in ice to room temperature under an atmosphere of oxygen-free nitrogen. 

The wavelengths at which most of the components of a primitive Earth atmosphere absorb lie, with few exceptions, under 200 nm. The exceptions include ammonia (< 230 nm), hydrogen sulphide (<260 nm) and ozone (180-300 nm). However, ozone was probably present in the primeval atmosphere only in trace amounts, since free oxygen was only available in extremely low concentrations. The young Earth thus had no protective ozone layer, so short-wavelength UV irradiation could readily penetrate the atmosphere. 

CC12FCC1F2. These compounds are non-toxic and non-flammable, and their thermodynamic properties are ideally suited for the compression/ expansion cycle in cooling and heat pump appliances. However, CFCs are chemically very inert, so when they are vented into the atmosphere, they do not react with atmospheric constituents. They diffuse unscathed first into the troposphere, then penetrate slowly into the stratosphere. There, the solar UV radiation photodissociates these compounds, liberating free chlorine atoms (the C-Cl bond is weaker than the C-F bond). The chlorine atoms react with atmospheric O3 to form chlorine oxide, which in turn reacts with atmospheric atomic oxygen regenerating chlorine atoms ... 

Before the appearance of photosynthetic organisms, there was no free oxygen in the atmosphere. Oxygen accumulated slowly as the numbers of photosynthesizing green algae and plants increased. 

All operations must be carried out under a nitrogen atmosphere, free from oxygen and moisture. The solvents must be dried by the usual methods and be saturated with nitrogen.13... 

The various kinds of pitch used here were carbonized in a porcelain boat within a heated horizontal cylindrical retort. The temperature of the sample, which was measured by means of a thermocouple placed just above the boat, could be maintained constant to within 1°C. All carbonization runs were carried out with an atmosphere of oxygen-free nitrogen. The heated material was cooled to room temperature before examination. 

There was no free oxygen or nitrogen in the primitive atmosphere. How and why did the composition of air change ... 

Astronomical observations in red-giant stars of molecular bands in the molecules TiO and TiC have provided a sensitive test of the transition from an O-rich star to a C-rich star ( carbon star ). Ifthe star s atmosphere contains more oxygen than carbon, free oxygen remains after chemically forming as much of the tightly bound CO molecule as is possible. Such stars reveal bands ofTiO in their spectra. Conversely, in carbon stars, excess C remains after the formation of the maximum amount of CO molecules. These stars reveal bands of TiC in their spectra. And it is from the atmospheres of such stars that the mainstream SiC presolar grains are recovered in meteorites. 

A ligandless and base-free Gu-catalyzed protocol for the coupling of arylboronic acids and potassium aryltrifluoro-borates with primary and secondary aliphatic amines and anilines was developed. The process utilized catalytic copper(n) acetate monohydrate or CuCl2 and 4 AMS in dichloromethane at slightly elevated temperatures under an atmosphere of oxygen (Equation (232)).1019-1021... 

Octakis[f-butyl]-l,2,3,4,5-telluratetrastannolane1 All operations are performed under an argon atmosphere with oxygen-free solvents. Hydrogen telluride is passed for 1 h through a solution of 5.0 g (4.2 mmol) of 1,4-diiodo-l, 1,2,2,3,3,4,4-octakis[f-butyl]tetrastannane n a mixture of 100 ml of toluene and 1 ml of triethylamine. The mixture is then filtered to remove precipitated triethylammonium iodide, the solvent is evaporated from the filtrate, and the residue is recrystallized from chloroform/hexane yield 2.4 g (55%) m.p. 170° (dec.). 

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