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PubMed2005

Coupled cluster calculation of the n --> pi* electronic transition of acetone in aqueous solution.

The combined linear response coupled cluster/molecular mechanics (CC/MM) scheme including mutual polarization effects in the coupling Hamiltonian is applied together with supermolecular CC methods to the study of the gas-to-aqueous solution blue shift of the n --> pi* excitation energy in acetone. The aug-cc-pVDZ basis set is found to be adequate for the calculation of this excitation energy. In the condensed phase, the shift in the excitation energy is obtained by statistical averaging over 800 solute-solvent configurations extracted from a molecular dynamics simulation. We find the shift to be around 1100-1200 cm(-1) depending on the specific model used to describe solvent polarization. The importance of including explicit polarization in both the molecular dynamics simulation as well as the CC/MM calculations is emphasized. Furthermore, the significant dependence of the excitation energy on the CO bond length of acetone is discussed.

Journal Article↗
PubMed2006

Structure and oxidation state of silica-supported manganese oxide catalysts and reactivity for acetone oxidation with ozone.

Silica-supported manganese oxide catalysts with loadings of 3, 10, 15, and 20 wt % (as MnO2) were characterized with use of X-ray absorption spectroscopy and X-ray diffraction (XRD). The edge positions in the X-ray absorption spectra indicated that the oxidation state for the manganese decreased with increasing metal oxide loading from a value close to that of Mn2O3 (+3) to a value close to that of Mn3O4 (+2(2)/3). The XRD was consistent with these results as the diffractograms for the supported catalysts of higher manganese oxide loading matched those of a Mn3O4 reference. The reactivity of the silica-supported manganese oxide catalysts in acetone oxidation with ozone as an oxidant was studied over the temperature range of 300 to 600 K. Both oxygen and ozone produced mainly CO2 as the product of oxidation, but in the case of ozone the reaction temperature and activation energy were significantly reduced. The effect of metal oxide loading was investigated, and the activity for acetone oxidation was greater for a 10 wt % MnOx/SiO2 catalyst sample compared to a 3 wt % MnOx/SiO2 sample.

Journal Article↗
PubMed2006

Computational study of the reaction of atomic oxygen with acetone in the gas phase.

Mechanisms and kinetics of the reaction of atomic oxygen with acetone have been investigated using ab initio quantum chemistry methods and transition state theory. The structures of the stationary points along the possible reaction pathways were obtained using the second-order Møller-Plesset theory and the coupled-cluster theory with single and double excitations with the triple-zeta quality basis sets. The energetics of the reaction pathways were calculated at the reduced second-order Gaussian-3 level and the extrapolated full coupled-cluster/complete basis set limit. The rate coefficients were calculated in the temperature range 200-3000 K, with the detailed consideration of the hindered internal rotation and the tunneling effect using Eckart and the semiclassical WKB approximations. It is shown that the predominant mechanism is the direct hydrogen abstraction producing hydroxyl and acetonyl radicals. Although the nucleophilic OC addition/elimination channel leading to CH3 and CO2 involves comparable barrier with the direct hydrogen abstraction channel, kinetically it cannot play any role in the overall reaction. It is predicted that the rate coefficients show positive temperature dependence in the range 200-3000 K and strong non-Arrhenius behavior. The tunneling effect plays a significant role. Moreover, the reaction has strong kinetic isotope effect. The calculated results are in good agreement with the available experimental data. The present rigorous theoretical work is helpful for the understanding of the characteristics of the reaction of atomic oxygen with acetone.

Journal Article↗
PubMed2006

Infrared spectra of the complexes of trifluoroethene with dimethyl ether, acetone, and oxirane: a cryosolution study.

Infrared spectra of solutions of trifluoroethene and dimethyl ether, acetone, or oxirane in liquid krypton and liquid argon have been studied. For each Lewis base the formation of a 1:1 complex with the Lewis acid was observed. The C-H stretching of trifluoroethene being perturbed by a strong Fermi resonance, the complexes with trifuloroethene-d were also investigated and showed that in each case the hydrogen bond between the acid and base is of the traditional, red-shifting type. The structures of the complexes were investigated using ab initio calculations. These indicate that with dimethyl ether and acetone two different isomeres can be formed, but with a single one detected in the solution in each case. The Fermi resonance in the complex with unlabeled trifluoroethene is discussed using data derived form ab initio potential and dipole hypersurface calculations. The complexation enthalpies of the complexes were obtained from temperature dependent studies of the solutions and are discussed in relation to the ab initio complexation energies and Monte Carlo free energy perturbation calculations of solvent effects.

Journal Article↗
PubMed2003

Photochemical alpha-cleavage of ketones: revisiting acetone.

The photochemical [small alpha]-cleavage of acetone is analyzed in view of recent results obtained for the isolated molecule in supersonic jets. The fluorescence decay time of the isolated molecule spans a range of more than six orders of magnitude, from approximately 10(-6) s near the origin of the S(0)-S(1) transition to less than 10(-12) s at about 20 kcal x mol(-1) excess energy. In contrast, the decay time of the excited singlet (S(1), (1)n pi) in the bulk is around 10(-9) s and independent of excitation wavelength. Initial excitation to the (1)npi state is followed by internal conversion (IC) to the ground state and intersystem crossing to the lowest-lying triplet. The rate constants of these processes are comparable to the radiative decay rate constant for excess energy up to 7 kcal x mol(-1) above the origin of the S(0)-S(1) transition. Beyond that energy, the triplet state becomes dissociative and the ISC rate becomes much larger than other processes depleting S(1). The primary reaction on the triplet surface is a barrier-controlled alpha-cleavage to form the triplet radical pair CH(3)(*)+ CH(3)CO(*). Direct reaction from the S(1) is negligible, and the non-quenchable reaction (by triplet quenchers) observed in the bulk gas phase is due to hot triplet molecules that dissociate on the timescale of 10(-12) s or less. The singlet-state decay time measured in the bulk (approximately 1-2 ns) arises from collision-induced processes that populate low-lying levels of S(1). The analysis is aided by detailed state-resolved studies on related molecules (in particular formaldehyde and acetaldehyde) whose photophysics and photochemistry parallel those of acetone.

Journal Article↗
PubMed2000

The effect of occlusion on epidermal penetration of parabens from a commercial allergy test ointment, acetone and ethanol vehicles.

The efficacy of topical allergy screening systems relies on the ability of test agents to effectively penetrate the stratum corneum from applied vehicles and reach the viable cells involved in the cutaneous immune response system. There is very little evidence in the dermatologic literature to justify the choice and suitability of vehicles used in many allergy test systems and the effectiveness of occlusion, reported to have variable effects on solute penetration, often employed in combination with these systems. In this study we evaluated the in vitro human epidermal penetration of a mixture of paraben ester preservatives from a commercially available test ointment and two commonly employed solvent vehicles (acetone and ethanol), together with the effect of occlusion on the rate of delivery from these systems. Parabens were applied as finite doses (5 mg per cm2) to epidermal membranes mounted in horizontal Franz-type diffusion cells. At intervals of 2 h for a total of 10 h the receptor phase (20% ethanol in distilled water) was completely removed and replaced. Occlusion was effected by the placement of a piece of high density polyethylene (20 microm) over the application site immediately after dosing. Concentrations of parabens in receptor fluid and remaining in the epidermis at the end of the study were determined by high-performance liquid chromatography. There was a significant change in the epidermal flux of parabens from each of the vehicles following occlusion. Whereas increases were observed for the acetone and ethanol vehicles a decrease was seen following occlusion of the ointment formulation. Changes in flux appeared to result from a significant decrease in the epidermal partitioning of the esters following occlusion of the ointment and primarily by an increase in paraben epidermal diffusivity (estimated from changes in flux/retention) following occlusion of the solvent vehicles. These studies show that the effects of occlusion are strongly vehicle dependent, having wide implications for optimization of this technique with a range of topically applied solutes.

Cell Membrane Permeability↗
PubMed2005

Ab initio n-electron valence state perturbation theory study of the adiabatic transitions in carbonyl molecules: formaldehyde, acetaldehyde, and acetone.

The application of the recently developed second-order n-electron valence state perturbation theory (NEVPT2) to small carbonyl molecules (formaldehyde, acetaldehyde, and acetone) is presented. The adiabatic transition energies are computed for the singlet and triplet n-->pi(*), pi-->pi(*), and sigma-->pi(*) states performing a full geometry optimization of the relevant states at the single state CASSCF level and taking into account the zero point energy correction in the harmonic approximation. The agreement with the known experimental values and with previously published high level calculations confirms that NEVPT2 is an efficient tool to be used for the interpretation of molecular electronic spectra. Moreover, different insight into the nature of the excited states has been obtained. Some of the transitions presented here have never been theoretically computed previously [(3)(pi-->pi(*)) and (3)(sigma-->pi(*)) adiabatic transitions in acetaldehyde and acetone] or have been studied only using moderate level (single reference based) ab initio methods (all adiabatic transitions in acetaldehyde). In the present work a consistent disagreement between NEVPT2 and experiment has been found for the (3)(pi-->pi(*)) adiabatic transition in all molecules: this result is attributed to the low intensity of the transition to the first vibrational levels of the excited state. The n-->pi(*) singlet and triplet vertical transition energies are also reported for all the molecules.

Journal Article↗
PubMed2002

Spectrophotometric determination of some chemotherapeutic agents using acetyl acetone.

Acetyl acetone is introduced as a new coupling agent for the spectrophotometric determination of some chemotherapeutic agents, such as metoclopramide, dapsone, p-aminobenzoic acid, and cisapride in both pure and dosage forms. The method is based on the diazo-coupling reaction of these chemotherapeutic agents with a new coupling agent, acetyl acetone, in an alkaline medium. The optimum reaction conditions and other analytical parameters are evaluated. The influence of the substrates commonly employed as excipients with these chemotherapeutic agents has been studied. The method is simple, rapid, and sensitive. The results obtained compare favorably with those obtained with other reference methods.

4-Aminobenzoic Acid↗
PubMed1981

Specific binding of the tumor promoter TPA in various mouse organs as measured by a "cold acetone-filter assay'.

Rapid, specific, saturable and partially reversible binding of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate ([3H]TPA) to a particulate fraction of mouse brain can be demonstrated by means of a "cold acetone-filter assay'; by washing with cold acetone at -20 degree C, nonspecific binding of the highly lipophilic [3H]TPA to membranes can be reduced to approximately 10% of the total binding. A comparative study of homogenates of several organs with this test revealed specific [3H]TPA binding/microgram DNA in the order brain much greater than lung approximately equal to spleen approximately equal to liver approximately equal to kidney approximately equal to thymus approximately equal to ovaries. Specific binding sites were also detected in 600 x g supernatant fractions of homogenates from epidermis, forestomach, glandular stomach and small intestine. Competition experiments showed displacement of [3H]TPA by TPA greater than phorbol-12,13-didecanoate greater than 12-deoxyphorbol-13-tetradecanoate greater than phorbol-12,13-dibutyrate (PDBu) greater than phorbol-12,13-diacetate greater than 4-O-methyl-TPA greater than 4 alpha-phorbol-12,13-didecanoate in the brain particulate fraction. Specific [3H]TPA binding is sensitive to heat, periodate and dithiothreitol, but is relatively insensitive to urea or to 1-5% solutions of several common detergents. It is estimated that the present binding test is approximately 500 times more sensitive than the widely-accepted [3H]PDBu assay; perhaps more important, the present method employs TPA, which is extremely effective both as a tumor promoter in vivo and as a pleiotropic effector of cells in vivo and in vitro.

Animals↗
PubMed1985

Extinction coefficients of chlorophyll a and B in n,n-dimethylformamide and 80% acetone.

We found inconsistencies in the commonly used data for chlorophyll analysis in 80% acetone. Recently developed extinction coefficients for chlorophyll b in N,N-dimethylformamide (DMF) based on values from 80% acetone are low as a result of these inconsistencies. We determined extinction coefficients of chlorophyll a (Chl a) and chlorophyll b (Chl b) in DMF for wavelengths of 618 to 665 nanometers. The simultaneous equations necessary for quantifying Chl a, Chl b, or total Chl in DMF in the absence of other chlorophyllous pigments are: Chl a = 12.70A(664.5) - 2.79A(647); Chl b = 20.70 A(647) - 4.62A(664.5); total Chl = 17.90A(647) + 8.08A(664.5), where A = absorbance in 1.00 centimeter cuvettes and Chl = milligrams per liter.N,N-Dimethylformamide is a very convenient solvent for Chl extraction since it is effective on intact plant parts and Chl is quite stable in DMF. There was no difference in the amount of Chl extracted when plant tissue was stored for 1 or 3 days at three temperatures, with or without solvent added.

Journal Article↗
PubMed2004

Bis(acetone-kappaO)bis(N,N'-dimethylethylenediamine-kappa(2)N,N')copper(II) diperchlorate.

The title compound, [Cu(C(4)H(12)N(2))(2)(C(3)H(6)O)(2)](ClO(4))(2), is the first structurally characterized Cu(II) complex having acetone as axial ligands. The complex adopts an elongated octahedral trans-[CuN(4)O(2)] coordination geometry, with the Cu atom having 222 site symmetry. The axial Cu-O(acetone) and in-plane Cu-N bond lengths are 2.507 (5) and 2.041 (3) A, respectively.

Journal Article↗
PubMed2006

An unusual example of a linearly coordinated acetone ligand in a six-coordinate iron(II) complex.

The title compound, acetonediaqua[2,6-bis(3-tert-butylpyrazol-1-yl)pyridine]iron(II) bis(tetrafluoroborate) acetone disolvate, [Fe(C19H25N5)(C3H6O)(H2O)2](BF4)(2).2C3H6O, contains a C2-symmetric six-coordinate complex dication, with an acetone ligand in its equatorial plane that is linearly coordinated by symmetry (Fe-O=CMe2=180 degrees). This is a consequence of close steric contacts between the coordinated carbonyl group and the two distal tert-butyl substituents on the tridentate ligand.

Journal Article↗
PubMed2001

Mechanistic aspects of cyanogenesis from active-site mutant Ser80Ala of hydroxynitrile lyase from Manihot esculenta in complex with acetone cyanohydrin.

The structure and function of hydroxynitrile lyase from Manihot esculenta (MeHNL) have been analyzed by X-ray crystallography and site-directed mutagenesis. The crystal structure of the MeHNL-S80A mutant enzyme has been refined to an R-factor of 18.0% against diffraction data to 2.1-A resolution. The three-dimensional structure of the MeHNL-S80A-acetone cyanohydrin complex was determined at 2.2-A resolution and refined to an R-factor of 18.7%. Thr11 and Cys81 involved in substrate binding have been substituted by Ala in site-directed mutagenesis. The kinetic measurements of these mutant enzymes are presented. Combined with structural data, the results support a mechanism for cyanogenesis in which His236 as a general base abstracts a proton from Ser80, thereby allowing proton transfer from the hydroxyl group of acetone cyanohydrin to Ser80. The His236 imidazolium cation then facilitates the leaving of the nitrile group by proton donating.

Aldehyde-Lyases↗
PubMed1977

Acne vulgaris: treatment with topical benzoyl peroxide acetone gel.

The topical effect on acne of a benzoyl peroxide acetone gel was studied over an eight week period and simultaneously compared with the effect of a benzoyl peroxide lotion and a vitamin A acid cream. The three formulations produced a significant reduction in the number of comedones. The two benzoyl peroxide formulations substantially reduced the number of papules, but this effect was not observed to a significant degree with the vitamin A acid. Burning sensation following application, a common problem with the benzoyl peroxide alcohol gels, was not reported by patients using the benzoyl peroxide acetone gel.

Acne Vulgaris↗
PubMed2004

[Isolation and elucidation of antioxidant constituents from acetone extract in root of Scutellaria rehderiana].

OBJECTIVE: To isolatate and elucidate the antioxidant constituents from acetone extract of Scutellaria rehderiana. METHOD: Chemical constituents were isolated by several column chromatographies and their structures were elucidated on the basis of standard compounds and spectral analysis. RESULT: Five compounds, oroxylin A, wogonin, baicalein, ganhuangenin, ganhuangemin were isolated from acetone extract of S. rehderiana. Baicalin was obtained from methanol extract of S. rehderiana. CONCLUSION: Ganhuangemin was isolated from the plant for the first time. Baicalein and ganhuangenin have stronger antioxidant activity than that of BHT (butylated hydroxytoluene).

Antioxidants↗
PubMed1977

Detection of antilymphocyte antibodies in patients with systemic lupus erythematosus by indirect immunofluorescence on acetone-fixed lymphocytes.

Antilymphocyte antibodies in normal and SLE sera were found to react with lymphocytes fixed in acetone at -30 degrees C. for 10 minutes. At a dilution of 1:40, 3.7 per cent of normal and 90.9 per cent of SLE sera were positive with the use of indirect immunofluorescence with a pepsin-digested, FITC-labeled anti-Fab serum. The reaction was independent of temperature between 4 degrees and 37 degrees C. Three patterns of staining were seen in the lymphocyte surface: reticular, ring, and globular. The ring pattern appeared to correlate with IgM, and the reticular and globular patterns with IgG antilymphocyte antibodies. Absorption with lymphocytes, insolubilized extracts of rat liver and kidney, and human brain revealed that antilymphocyte and ANA activity could be independently removed. Variation in reactivity with cells from different normal donors was similar to that seen with the microcytotoxicity test. Acetone-fixed lymphocytes appear to be a much more sensitive target than viable cells in suspencion in IIF tests for antilymphocyte antibodies. The IIF test with fixed cells also appears slightly more sensitive than cytotoxicity testing and has the advantage of allowing storage of target cells.

Antibodies, Antinuclear↗
PubMedDate not supplied

[Hygienic evaluation of acetone cyanohydrin transformation in water].

The study of acetone cyanohydrin (ACH) showed that it is an unstable substance. Its stability in water depends on pH of water and less so on its initial concentration; water temperature and biota are insignificant. Acetone and cyanid-ion, forming from ACH, after 20 days are transformed into a complex of cyan compounds.

Biodegradation, Environmental↗