PubMed · 11605327
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2001. Acetone.. https://pubmed.ncbi.nlm.nih.gov/11605327/
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A detailed thermochemical analysis of the alpha-cleavage and decarbonylation reactions of acetone and several ketodiesters was carried out with the B3LYP/6-31G* density functional method. The heats of formation of several ground-state ketones and radicals were calculated at 298 K to determine bond dissociation energies (BDE) and radical stabilization energies (RSE) as a function of substituents. Results show that the radical-stabilizing abilities of the ketone substituents play a very important role on the thermodynamics of the alpha-cleavage and decarbonylation steps. An excellent correlation between calculated values and previous experimental observations suggests that photochemical alpha-cleavage and decarbonylation in crystals should be predictable from knowledge of excitation energies and the RSE of the substituent.
Mn(hfacac)(3) is an easily prepared and reactive oxidant (hfacac = hexafluoroacetylacetonate). It forms stable solutions in benzene and methylene chloride but is rapidly reduced in acetonitrile, DMSO, acetone, and ethers. It is reduced by ferrocene to give the Mn(II) complex [Cp(2)Fe][Mn(hfacac)(3)], which has been structurally characterized. Mn(hfacac)(3) also rapidly oxidizes 1-acetylferrocene, 1,1'-diacetylferrocene, and tris(4-bromophenyl)amine. Based on an equilibrium established with tris(2,4-dibromophenyl)amine, a redox potential of 0.9 +/- 0.1 V vs Cp(2)Fe(+/0) is calculated. Mn(hfacac)(3) oxidizes 9,10-dihydroanthracene (DHA) cleanly to anthracene, with a bimolecular rate constant of 6.8 x 10(-4) M(-1) s(-1) at 25 degrees C in benzene solution. In the presence of small amounts of water, the manganese(II) product is isolated as cis-Mn(hfacac)(2)(H(2)O)(2), which has also been structurally characterized. Mn(hfacac)(3) also oxidizes xanthene to 9,9'-bixanthene, 1,4-cyclohexadiene to benzene, and 2,4-di-tert-butylphenol to the phenol dimer. Toluene and substituted toluenes are oxidized to tolylphenylmethanes. Product analyses and relative rates--for instance that p-methoxytoluene reacts much faster than toluene--indicate that the more electron rich substrates react by initial electron transfer to manganese. For the less electron rich substrates, such as 1,4-cyclohexadiene, a mechanism of initial hydrogen atom transfer to Mn(hfacac)(3) is suggested. The ability of Mn(hfacac)(3) to abstract H* is reasonable given its high redox potential and the basicity of [Mn(hfacac)(3)](-). In CH(2)Cl(2) solution, oxidation of DHA is catalyzed by chloride ion.
Removal of low levels of organic pollutants can be quite challenging to many water treatment processes. Ketones, such as acetone, are often found in groundwaters and wastewaters at levels too low for supporting a bioreactor, yet since acetone is so soluble, it does not adsorb onto activated carbon very well, nor does it volatilize from water influent using air stripping. This study was undertaken to evaluate three advanced oxidation processes for their comparative ability to remove acetone from aqueous media. Optimization of the oxidation processes was attempted via adjustments of oxidizer inputs. The results indicated that all of the AOPs tested showed promise for removing acetone from water; however, ozonated systems undergoing UV photolysis achieved the highest rate and extent of treatment observed.