Search results for "ACETONE"
showing 10 items of 350 documents
Clerodane diterpenoids from Salvia splendens.
2006
Four new clerodane diterpenoids, salvisplendins A-D (1-4), have been isolated from an acetone extract of the flowers of SalVia splendens, together with an artifact (5), arising from salvisplendin D (4) by addition of diazomethane, and the already known clerodane olearin (6). The structures of the new compounds (1-5) were established mainly by 1D and 2D NMR spectroscopic studies and, in the case of salvisplendin A (1), by chemical correlation with splenolide B (7). Complete 1H and 13C NMR assignments for olearin (6), not published hitherto, are also reported.
Concave macrobicycles: Absorption spectra, luminescence properties, and endocavital complexation of neutral organic guests
1996
By a mild modified Eglinton coupling a series of diynebridged macrobicyclic hosts capable of endocavital complexation were synthesized and their structures and complexation properties investigated by X-ray analysis. The inclusion of DMSO in 7 suggests a direct correlation between steric fit and orientation of the guest. On the basis of this hypothesis, the orientation of acetone in an endocavital inclusion of 2 was predicted and verified by X-ray analysis. Comparison of the single-crystal X-ray structures of the vacant macrobicycle 3 and of a family of macrobicycles showing endocavital or “pocket” complexation of neutral organic guests suggests that torsion of the cavities upon complexation…
The oligomerisation of 3-hydroxy-1-alkynes with palladium(II) diketonates and phosphorus ligands as the catalytic system
1993
Abstract 3-Methylhex-1-yne-3-ol has been oligomerised by use of Pd(II) acetylacetonate with 31 different phosphorus ligands as catalyst, yielding a dimer (2,4-disubstituted but-1-en-3-yne) and a linear trimer (1,4,6-trisubstituted hexa-1,3-dien-5-yne) as the two main products. By input-output relations a variation of the diketonate and the P ligand, as weil as an alteration of the phosphorus/palladium ratio, has been connected with product ratios as dependent variables. Phosphines produced three association steps up to a cone angle of 170°; the third step representing a stop complex. For the first association the activity of the catalytic system and the portion of the 2,4-dimer increased wi…
A theoretical study of carbon-carbon bond formation by a Michael-type addition.
2012
A theoretical study of the Michael-type addition of 1,3-dicarbonyl compounds to α,β-unsaturated carbonyl compounds has been performed in the gas phase by means of the AM1 semiempirical method and by density functional theory (DFT) calculations within the B3LYP and M06-2X hybrid functionals. A molecular model has been selected to mimic the role of a base, which is traditionally used as a catalyst in Michael reactions, an acetate moiety to modulate its basicity, and point charges to imitate the stabilization of the negative charge developed in the substrate during the reaction when taking place in enzymatic environments. Results of the study of six different reactions obtained at the three di…
Ionic Liquids as Entrainers in Extractive Distillation: Isobaric Vapor−Liquid Equilibria for Acetone + Methanol + 1-Ethyl-3-methylimidazolium Triflu…
2006
Isobaric vapor−liquid equilibria for the binary systems acetone + methanol, acetone + 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][triflate]), and methanol + [emim][triflate] as well as the vapor−liquid equilibrium for the acetone + methanol + [emim][triflate] ternary system have been obtained at 100 kPa using a recirculating still. The addition of the ionic liquid to the solvent mixture produced an important salting-out effect, and the azeotrope tended to disappear for small contents of ionic liquid. The experimental binary data sets were independently fitted with the electrolyte NRTL model, and the parameters of Mock's model were estimated for each binary system. These pa…
Characteristics of haloethylene-induced acetonemia in rats.
1980
A series of halogenated ethylenes (vinyl chloride, vinylidene fluoride,cis- andtrans-1,2-dichloroethylene, perchloroethylene) induces increased acetone exhalation in rats. Exposures of differently pre-treated rats to vinylidene fluoride suggest that a metabolite of the haloethylene must be envolved in eliciting this formation of acetone. This conclusion is based on (a) dependence of acetone exhalation on the concentration of vinylidene fluoride, (b) effect of inducing agents, (c) effect of pyrazol, a metabolic inhibitor, (d) effect of cysteine, (e) effect of hypoxia and (f) the time course of acetone exhalation.
Nanocomposites based on esterified colophony and halloysite clay nanotubes as consolidants for waterlogged archaeological woods
2017
We have designed an innovative protocol for the consolidation of waterlogged archaeological woods by using acetone mixtures of halloysite clay nanotubes and a chemically modified colophony (Rosin). Firstly, we have investigated the thermal properties of HNTs/Rosin nanocomposites, which have been prepared by means of the casting method from acetone. The HNTs content have been systematically changed in order to study the influence of the inorganic filler on the thermal stability and glass transition process of Rosin. We have observed that the thermal properties of the hybrids are affected by the specific HNTs/Rosin interactions. Then, acetone dispersions of HNTs/Rosin composites at variable f…
Assessment of the antioxidant and antibacterial activities of different olive processing wastewaters.
2017
Olive processing wastewaters (OPW), namely olive mill wastewater (OMW) and table-olive wastewaters (TOW) were evaluated for their antibacterial activity against five Gram-positive and two Gram-negative bacteria using the standard disc diffusion and thin layer chromatography (TLC)-bioautography assays. Disc diffusion screening and bioautography of OMW were compared to the phenolic extracts of table-olive brines. Positive activity against S. aureus was demonstrated. The optimization of chromatographic separation revealed that hexane/acetone in the ratio of 4:6 was the most effective for phenolic compounds separation. A HPLC-MS analysis was performed showing that only two compounds, hydroxytyr…
Complexes of organometallic compounds
1972
Abstract The configurations of (CH 3 ) 3 PbNCS, (C 6 H 5 ) 3 PbNCS, (C 6 H 5 ) 2 Pb(NCS) 2 , (C 6 H 5 ) 3 Pb(NCS) 2 − and (C 6 H 5 ) 2 Pb(NCS) 4 2− have been investigated in the solid and (except for the insoluble diphenyl derivative) in solution. From infrared spectroscopy it is deduced that the compounds are isothiocyanates in both states, and there is evidence for a polymeric nature of the solid neutral species involving bridging through NCS. PMR and osmometric investigations show that five-coordinate species (CH 3 ) 3 Pb(NCS)·(CH 3 ) 2 CO are present in acetone solution. Possible configurations are discussed.
Production of a Recombinant Catechol 2,3-Dioxygenase for the Degradation of Micropollutants
2017
Phenolic compounds such as catechol represent a particular type of micropollutant whose high stability prevents rapid decay and metabolization in the environment. We successfully cloned a catechol 2,3-dioxygenase (C2,3O) from Pseudomonas putida mt-2 and expressed it in Escherichia coli BER2566. The biomass isolated from shake-flask fermentations was used to partially purify the enzyme. The enzyme proved unstable in clarified liquid fractions (50 mM Tris buffer, pH 7.6) and lost more than 90% of its activity over 7 h at 25 °C. In the presence of 10% acetone, the process was slowed down and 30% residual activity was still present after 7 h incubation. Storage of the enzyme in clear liquid fr…