Acetone from decomposition

Yields of excited states from 1,2-dioxetane decomposition have been determined by two methods. Using a photochemical method (17,18) excited acetone from TMD is trapped with /n j -l,2-dicyanoethylene (DCE). Triplet acetone gives i7j -l,2-dicyanoethylene with DCE, whereas singlet acetone gives 2,2-dimethyl-3,4-dicyanooxetane. By measuring the yields of these two products the yields of the two acetone excited states could be determined. The yields of triplet ketone (6) from dioxetanes are determined with a similar technique. 

During reciystallisation of technical material from acetone, explosive decomposition occurred. Non-explosive decomposition occurred when the nitrile was heated alone, or in presence of methanol. 

The quantum yield for decomposition of acetone from the triplet state is about 0.40 at 40°, and the quantum yield of phosphorescence is about 0.02.308 At least 407o of the initially excited molecules are not accounted for by either emission or chemical reaction, and thus must undergo some kind of radiationless decay to the ground state, presumably mostly from the triplet state. Recent studies of hexafluoro-acetone317 indicate that approximately half the triplet molecules formed by intersystem crossing undergo radiationless decay. 

The formation of large yields of acetone from n-pentane, however, has led to the suggestion that decomposition analogous to that of the of-dihydroperoxides is important... 

The population of surface defects and coordination vacancies drives alkoxide and carboxylate formation and decomposition. When cations have at least two coordination vacancies, bimolecular reactions are possible (e.g., acetone from acetate ions, dimethylether from methoxy groups). 

With the exception of formic acid, the lower fatty acids are quite stable np to relatively high temperatures. Cahours and Berthelot early notedos the thermal stability of these acids, and the latter reported that acetic acid did not decompose until above a dull red heat. More recently Senderens showed that acetic, propionic, /i-butyric, isobutyric, and isovaleric acids were perfectly stable at temperatures as high as 460° C.os At higher temperatures these acids undergo pyrogenic decomposition to yield simple and stable substances. In the case of acetic acid, Nef 01 reported the presence of methane, carbon dioxide, carbon monoxide, ethylene, hydrogen, and acetone in the products from decomposition. 

McMillan (1962) photolyzed r-butyl nitrite at 253.7 and 313.0 nm and found that acetone was the major product, with CH3ONO2 and N2 as minor products. He noticed that the acetone quantum yield decreased with increasing pressure. Therefcne he interpreted the acetone as coming from decomposition of an excited r-butoxyl radical, which could be stabilized by collision. Thus the primary process is... 

It may be destroyed in several ways. One method is as follows (Aldrich 1995). The solid or its solution is dissolved or diluted in large volume of water. Diluted acetic acid or acetone is then slowly added to this solution in a well-ventilated area. Hydrogen generated from decomposition of borohydride should be carefully vented out. The pH is adjusted to 1. The solution is then allowed to stand for several hours. It is then neutralized to 7, and the solution is then evaporated to dryness. The residue is then buried in a landfill site approved for hazardous waste disposal. Sodium borohydride may be destroyed in the laboratory by alternative methods mentioned for other hydrides. 

The hydroperoxide concentrate is fed to a second reactor where a selective decomposition takes place in the presence of dilute sulfuric acid and well-controlled reaction conditions yielding primarily phenol and acetone. The reactor effluent is passed through a separator to remove the water, acid, and salts followed by a series of fractionation steps to isolate both the phenol and acetone from undesired by-products. 

The ORR electrochemistry in gas saturated 0.05 mol dm" H SO was investigated at 25 °C using a platinum RDE, with or without organic impurities in the solution. These organic impurities are supposed to come into the cathode catalyst layer through the catalyst ink or MEA binders (2-propanol, Triton-X 100), from decomposition products from MEA binders and membranes (acetone, 1-hexanal, and 1-octanal) or from crossed-over anode fuel (methanol) through the polymer electrolyte in the case of direct methanol fuel cells. 

Surprisingly, the yield of excited products (triplet and singlet acetone) from dimethyl-dioxetanone (21) is only 5% of that observed in tetramethyl dioxetane decomposition, although the thermolysis of (23) is ca 84 kJ/mol. more exothermic... 

Dissolve 13 g. of sodium in 30 ml. of absolute ethanol in a 250 ml. flask carrying a reflux condenser, then add 10 g. (9 5 ml.) of redistilled ethyl malonate, and place the flask on a boiling water-bath. Without delay, add a solution of 5 3 g. of thiourea in a minimum of boiling absolute ethanol (about 100 ml.). The sodium salt of thiobarbituric acid rapidly begins to separate. Fit the water-condenser with a calcium chloride guard-tube (Fig. 61, p. 105), and boil the mixture on the water-bath for 1 hour. Cool the mixture, filter off the sodium salt at the pump and wash it with a small quantity of cold acetone. Dissolve the salt in warm water and liberate the acid by the addition of 30 ml. of concentrated hydrochloric acid diluted with 30 ml. of water. Cool the mixture, filter off the thiobarbituric acid, and recrystallise it from hot water. Colourless crystals, m.p. 245 with decomposition (immersed at 230°). Yield, 3 5 -4 0 g. 

Some unsaturated ketones derived from acetone can undergo base- or acid-catalyzed exothermic thermal decomposition at temperatures under 200°C. Experiments conducted under adiabatic conditions (2) indicate that mesityl oxide decomposes at 96°C in the presence of 5 wt % of aqueous sodium hydroxide (20%), and that phorone undergoes decomposition at 180°C in the presence of 1000 ppm iron. The decomposition products from these reactions are endothermic hydrolysis and cleavage back to acetone, and exothermic aldol reactions to heavy residues. 

Excitation appears to be general for this reaction but yields of excited products vary substantially with the substituent R. The highest yield reported is from tetramethyl-l,2-dioxetane [35856-82-7] (TMD) where the yield of triplet acetone is 50% of total acetone formed (18,19). Probably only one carbonyl of the two produced can be excited by the thermal decomposition, and TMD provides 100% of the possible yield of triplet acetone. Singlet excited acetone is also formed, but at the low yield of 0.1—0.3% (17—21). Other tetraaLkyldioxetanes behave similarly to TMD (22). 

A (4-Hydroxyphenyl)glycine. This derivative (23) forms aggregate spheres or shiny leaflets from water. It turns brown at 200°C, begins to melt at 220°C, and melts completely with decomposition at 245 —247°C. The compound is soluble in alkaU and mineral acid and sparingly soluble in water, glacial acetic acid, ethyl acetate, ethanol, diethyl ether, acetone, chloroform, and benzene. 

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