Oxygen balloons

It is recommended to replace the oxygen balloon for an argon balloon after 3.5 hours extensive exposure to 02 can have an adverse influence on the reaction. 

In 2007, Fujii, Ohno and their coworkers developed an efficient one-pot Buch-wald-Hartwig /V-arylation and oxidative coupling reaction to synthesize carbazoles (Scheme 27) [95]. Typically, Pd-catalyzed N-arylation of anilines with aryl triflates was conducted in toluene under the standard conditions. After completion of the N-ary I at ion as determined by TLC, acetic acid was added and an oxygen balloon was connected to the reaction flask (oxygen conditions) or it was subjected to air by an open system (air conditions). The protocol afforded various types of functionalized carbazoles in good to excellent yields (46->99%). 

Oestxeich found that the direct arylation of indolines could be accomplished without over oxidation to the corresponding indole under palladium-catalysis with air (open flask), oxygen (balloon), or copper(II) acetate as the oxidant. Indolines can be unsubstituted or substituted as C2/C3 and the reaction performs well on gram scale (250, 18 examples, 18—90% isolated yield) (140L6020).A directed C2-functionalization/C7-alkenylation was discovered by Xu,Yi, and colleagues. With a rhodium catalyst, indole derivatives were functionalized with acetates at C2 (22 examples, 62—92% yield) the newly obtained products could be alkenylated at C7 with a rhodium/copper system (251,3 examples, 68—78% yield) (14CC6483). 

Catalytic reaction. To a solution of a-azidostyrene (43.6 mg, 0.30 mmol) and 1-phenylcyclopropanol (48.4 mg, 0.36 mmol) in MeOH (3.0 mL) was added Mn(acac)3 (10.6 mg, 0.03 mmol) at room temperature under nitrogen atmosphere. After 5 min, HCl (0.20 mL, 0.60 mmol, 3.0 M in MeOH) was added and the nitrogen balloon was then replaced by oxygen balloon. The reaction mixture was heated at 40°C for 1 h and quenched with pH 9 ammonium buffer, and then extracted twice with ethyl acetate. The combined organic extracts were washed with brine, dried over MgS04, and concentrated. Purification of the crude product by flash column chromatography (silica gel hexane ethyl acetate = 98 2) afforded the pure product. 

Methylene blue (5.00 mg, 0.0170 mmol) was added to a solution of ( )-tri-dachiahydropyrone (9) (28.0 mg, 0.0850 mmol) in methanol (10 mL). The mixture was purged with oxygen for 30 min via an oxygen balloon and outlet needle, after which time the outlet needle was removed, and the solution irradiated with a mercury lamp (125 W) for 5 h. The mixture was then concentrated under reduced pressure, and the residue purified by preparative TLC (10 % EtOAc in petrol) to afford oxytridachiahydropyrone (10) (30.0 mg, 97 %) as a colourless oil. 

Reaction conditions Toluene, room temperature, oxygen (balloon)... 

Reactions of benzyl alcohol with ketones. CS2CO3 (980 mg, 3 nunol) and the catalyst, Au/ AIO(OH) (69 mg, 1.0 mol % of Au) were added to a solution of ketonic compound 3(1 mmol) and benzyl alcohol (324 mg, 3 mmol) in toluene (3 mL) in a 10 mL tube. The tube with a rubber stopper was connected with an oxygen balloon through a needle, and the mixture was stirred at room temperature for 24-30 h. On completion of the reaction, the crude a,p-unsaturated carbonyl compound product 4 was obtained by removal of the solvent from the filtrate followed by proper purification. Characterization of each product was done on the basis of GC and spectral data. 

Now here is a post from a very influential chemist named Spice-boy who has contributed quite a bit to this science (hypothetically of course). She decided to go ahead and apply the idea of using benzoquinone as the oxygen source. If this works it would mean that one would not have to use a balloon of O2 at all. thus making the entire apparatus much more simpler and causing an increase in the efficiency of oxygen uptake and transfer by the system. So let s see what Spiceboy dreamt might happen if this were actually applied ... 

This model is useful, first, because we can calculate in mathematical detail just how much push a billiard ball exerts on a cushion at each rebound, and, second, because exactly the same mathematics describes the pressure behavior of gas in a balloon. The success of the model leads to new directions of thought. For example, we might now wonder whether the pressure-volume behavior of oxygen, as shown in Table l-II (p. 14), can be explained in terms of the particle model of a gas. 

FIGURE 13.33 A small amount of catalyst—in this case, potassium iodide in aqueous solution—can accelerate the decomposition of hydrogen peroxide to water and oxygen, (a) The slow inflation of the balloon when no catalyst is present, (b) Its rapid inflation when a catalyst is present. 

A balloon filled with a mixture of hydrogen and oxygen is stable until a source of energy, such as a spark or flame, initiates the reaction. After the reaction begins, the formation of water releases enough energy to cause an explosion. 

After 80 minutes the connection with argon was replaced by a balloon filled with oxygen. The reaction mixture was stirred for 2.5 hours without removing the balloon filled with oxygen. 

PP/TTR-V consumer goods requiring low permeability to moisture, air and oxygen, competing with butyl rubber for example, inner tubes for bikes, bladders for balloons... 

The experiments on CO forms of the synthetic compounds were done with sample concentrations adjusted to 50 pM to give an absorbance of 1 over a 1 mm optical path at the Soret maximum. For the oxygen experiments, the samples were prepared as the CO complexes and covered with a balloon containing 3 1 mixture of CO to O. An additional photographic strobe lamp having a flash duration... 

If small volume experiments are carried out under exclusion of oxygen, an approved method is to use a balloon filled with inert gas attached to an otherwise closed apparatus. Likewise, using a balloon can easily compensate for changes in pressure. It is also recommended to use glove boxes when smaller amounts are to be handled under an inert gas. 

Because it is the lightest known gas, hydrogen was once used to float airships and aeronautical balloons. But it happens to be also extremely dangerous, and will burn readily (sometimes explosively) in oxygen. After a couple of spectacular disasters, the idea of passenger airships was abandoned in favor of airliners. Today, gas-filled balloons (often used for weather surveys) contain helium, which is also light, and safer than hydrogen. 

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