Acetone theoretical studies

Various liquid chromatographic techniques have been frequently employed for the purification of commercial dyes for theoretical studies or for the exact determination of their toxicity and environmental pollution capacity. Thus, several sulphonated azo dyes were purified by using reversed-phase preparative HPLC. The chemical strctures, colour index names and numbers, and molecular masses of the sulphonated azo dyes included in the experiments are listed in Fig. 3.114. In order to determine the non-sulphonated azo dyes impurities, commercial dye samples were extracted with hexane, chloroform and ethyl acetate. Colourization of the organic phase indicated impurities. TLC carried out on silica and ODS stationary phases was also applied to control impurities. Mobile phases were composed of methanol, chloroform, acetone, ACN, 2-propanol, water and 0.1 M sodium sulphate depending on the type of stationary phase. Two ODS columns were employed for the analytical separation of dyes. The parameters of the columns were 150 X 3.9 mm i.d. particle size 4 /jm and 250 X 4.6 mm i.d. particle size 5 //m. Mobile phases consisted of methanol and 0.05 M aqueous ammonium acetate in various volume ratios. The flow rate was 0.9 ml/min and dyes were detected at 254 nm. Preparative separations were carried out in an ODS column (250 X 21.2 mm i.d.) using a flow rate of 13.5 ml/min. The composition of the mobile phases employed for the analytical and preparative separation of dyes is compiled in Table 3.33. 

Vereecken, L. and Peelers, J. Theoretical study of the formation of acetone in the OH-initiated atmospheric oxidation of a-pinene, / PAjs. Chem. A, 104(47) 11140-11146, 2000. 

The predictive capabilities of results of theoretical calculations of isotope effects have again been questioned,94 following an experimental and theoretical study of the decarboxylation of 3-carboxybenzisoxazole at room temperature (Kemp s reaction). The experimentally determined 15N isotope effect in acetone is 1.0312 0.0006 and the 13C isotope effect (1.0448, 1.0445, 1.0472, and 1.0418 in 1,4-dioxane, acetonitrile, DMF, and water, respectively) is independent of solvent polarity even though the reaction rate is markedly solvent dependent. Theoretical models at die semiempirical (AMI, PM3, SAMI) and ab initio (up to B3LYP/6-31+ + G ) levels were all unable to predict die experimental results quantitatively. 

The hydroxymethyl cation forms of protonated ketones (264) and aldehydes (265) contribute to the resonance hybrid. Based on 13C NMR studies,94 548 551 the degree of contribution of the hydroxymethyl cation forms can be quite accurately estimated. Similar studies have been carried out using 170 NMR spectroscopy.552 Recent theoretical studies (MP2/6-31G level)553 for protonated acetone have supported the... 

Good test cases would be the solvent effects on the UV-vis absorption spectra of formaldehyde and acetone that have been the subject of innumerous theoretical studies. Innovative theoretical methods have been applied to formaldehyde (see also the compilation of results in [20,32,113,114,115,116]). Unfortunately the experimental result for formaldehyde in water is not clear because of chemical problems mostly associated to the aggregation and formation of oligomers. Therefore a better test case is the UV-vis spectra of acetone, because reliable experimental solvent shifts and several theoretical results are available (see the compilation of results in [117]). The Stokes shift of the n-rr transition of acetone has been critically discussed by Ohrn and Karlstrom [118], Grozema and van Duijnen [17] studied the solvatochromic shift of the absorption band of acetone in as much as eight different solvents. Acetone is known to shift the maximum of the n-rr band by 1500-1700 cm 1 when immersed in water [119,120,121], Using the conventional HF/6-31 G(d) point charges, Coutinho and Canuto [54] simulated acetone in water and performed INDO/CIS... 

Use of the tosyl derivative of cellulose for theoretical study is important. Cramer and Purves have prepared tosyl derivatives of acetone-soluble cellulose acetate. By treatment with sodium iodide, which replaces tosyl groups in the primary position by iodine, they have been able to measure the proportions of primary and secondary hydroxyl groups present in the original product. 

Sackett and Wolff83 measured the emission peaks of Nile Red in various polar solvents, ranging from 16260 cm-1 for acetone to 15040 cm-1 in water. A theoretical study of the absorption and emission solvatochromic properties of Nile Red (67) was presented recently by Han and coworkers84. The HB strength of the solvents around Nile Red was further studied by means of its fluorescence life time by Cser and coworkers85. A fourfold... 

Diau, E. W. G., Kotting, C., Zewail, A. H., Femtochemistry of Norrish Type I Reactions I. Experimental and Theoretical Studies of Acetone and Related Ketones on the S, Surface,... 

Sakurai, H., Kato, S., A Theoretical Study of the Norrish Type I Reaction of Acetone, THEOCHEM 1999, 462, 145 152. 

This range of possible adsorption modes for acetone prompted us to study the alternative adsorption possibilities for formaldehyde, as an example where the eno/ form is not possible, and acetone on Pt and Pd surfaces using periodic density functional theory. A previous theoretical study in this area has been published by Dumesic e al. however they have concentrated on the reaction pathway for hydrogenation of acetone over Pt(lll) assuming the r (0)-acetone is the only adsorbed state present. In this contribution we compare adsorption of acetone in the enol and keto isomers on both Pt(l 11) and Pd(l 11). 

Singlet sensitization of tetramethyl-l,2-dioxetan by pyrene results in the formation of triplet acetone.296 In a theoretical study related to the one reported in ref. 293, it was concluded that the triplet surface intersects the ground-state surface between (15) or (16) and cyclo-octatetraene. Evidence for triplet product... 

Recent theoretical studies of formaldehyde by Hachey et al. [64] and by the present authors [65] have revealed more features of the potential surfaces. The similarity between formaldehyde and acetone makes it possible to draw conclusions for the latter molecule based on the results obtained for formaldehyde, especially since the results obtained here for the states are similar in quality to those obtained by Hachey et al. The (o-- 77 ) potential has a minimum at r(CO) = 1.47A and crosses the Ai(t7— t7 ) surface close to this point. Bending the CH2 group out of the plane causes them to mix. The optimum bending angle was computed to be 46°. At shorter distances the surface mixes strongly with the n - 3d y) transition. It is likely that a similar situation obtains in acetone. Thus out-of-plane modes in combination with the CO stretch will allow for mixing of the and states. This will... 

Analysis of the liquid media influence on reaction (37.16) based on the experimental and theoretical studies shows that polar aprotic solvents (acetone, acetonitrile, etc.) can inhibit this process and the effective value increases by 20-30 kJ/mol (Table 37.6) [39]. 

Seminal studies by Gryko and co-workers revealed that replacement of the amide functionality with a thioamide group further increased catalyst acidity and thus activity [41], which has recently been confirmed by Shi s theoretical studies [42]. The addition of an acid proved to be beneficial for both the yield and enantio-selectivity [41b]. Aromatic aldehydes bearing either electron-withdrawing or electron-donating groups react with acetone in the presence of 0.2 mol% of... 

The initial rates at 25°C in isopropanol were studied as a function of the concentrations of water, acetone and acetophenone. The rate is inhibited by water (0-2.2 M) and by acetone (0.02-0.9 M) and shows saturation behavior with acetophenone above -0.05 M. The results were considered to be consistent wiA the direct transfer route since there was no kinetic evidence for hydride intermediates. Theoretical studies on analogous but greatly simplified systems have suggested a monohydride mechanism coupled with dissociation of one end of the diamine ligand, however, a later report supports a mechanism analogous to that discussed later in this section. 

This theoretical study is focused on the process combination of a distillation column and a pervaporation unit located in the side stream of the column. This hybrid membrane process can be applied for the separation of azeotropic mixtures such as acetone, isopropanol and water. Water is removed from the side stream of the column by pervaporation, while pure acetone and isopropanol are obtained at the top and bottom of the column. Detailed simulation studies show the influence of decisive structural parameters like side stream rate and recycle position as well as operational parameters like reflux ratio and mass flow on concentration profiles, membrane area and product compositions. 

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