Quantification of acetone emission from pine plants

Acetone emission from pine plants (pinus sylvestris) is measured by continuously stirred tank reactor. Under a constant light intensity, acetone emission rates increase exponentially with leaf temperature. When leaf temperature is kept constant, acetone emission increases with light intensity. And acetone emission in darkness is also detected. Acetone emitted from pine is quickly labeled by 13C when the plants are exposed to air with 630 mg/m313CO2. However, no more than 20% of acetone is 13C labeled. Acetone emission from pine may be due to both leaf temperature-controlled process and light intensity-controlled process. Based on these understandings, an algorithm is used to describe the short term acetone emission rates from pine.     

Palladium-catalyzed mono-α-arylation of acetone with aryl halides and tosylates

We report the first example of selective Pd-catalyzed mono-α-arylation of acetone employing aryl chlorides, bromides, iodides, and tosylates. The use of appropriately designed P,N-ligands proved to be the key to controlling the reactivity and selectivity. The reaction affords good yields with substrates containing a range of functional groups at modest Pd loadings using Cs(2)CO(3) as the base and employing acetone as both a reagent and the solvent.     

Derivatization of protonated peptides via gas phase ion—molecule reactions with acetone

The protonated [M + H]+ ions of glycine, simple glycine containing peptides, and other simple di- and tripeptides react with acetone in the gas phase to yield [M + H + (CH3)2CO]+ adduct ion, some of which fragment via water loss to give [M + H + (CH3)2CO - H2O]+ Schiff's base adducts. Formation of the [M + H + (CH3)2CO]+ adduct ions is dependent on the difference in proton affinities between the peptide M and acetone, while formation of the [M + H + (CH3)2CO - H2O]+ Schiff's base adducts is dependent on the ability of the peptide to act as an intramolecular proton "shuttle." The structure and mechanisms for the formation of these Schiff's base adducts have been examined via the use of collision-induced dissociation tandem mass spectrometry (CID MS/MS), isotopic labeling [using (CD3)2CO] and by comparison with the reactions of Schiff's base adducts formed in solution. CID MS/MS of these adducts yield primarily N-terminally directed a- and b-type "sequence" ions. Potential structures of the b1 ion, not usually observed in the product ion spectra of protonated peptide ions, were examined using ab initio calculations. A cyclic 5 membered pyrrolinone, formed by a neighboring group participation reaction from an enamine precursor, was predicted to be the primary product.     

Temperature dependent absorption cross-sections for acetone and n-butanone—implications for atmospheric lifetimes

Temperature dependent absorption cross-sections for acetone and n-butanone have been measured over the temperature range 260–360 K for 260 nm < λ < 360 nm. The temperature dependence of the cross-sections was fitted using simple, two-level models to allow the measured cross-sections to be extrapolated to upper tropospheric/lower stratospheric temperatures. Atmospheric photoexcitation rates were calculated as a function of altitude using both room temperature and temperature dependent cross-sections. Absorption in the 310–330 nm region makes the dominant contribution to solar photoexcitation in the troposphere and lower stratosphere. Neglect of the temperature dependence of the absorption cross-sections results in significant over-estimations of the solar photoexcitation rate for both acetone and n-butanone in the upper troposphere and lower stratosphere. Since the atmospheric lifetimes of these compounds are inversely proportional to the photoexcitation rate, current models may underestimate the upper atmospheric lifetimes of these compounds by ≈50%.     

Adsorbents for acetone in cyclohexane effuent employed in Ziegler-Natta catalyst process

Adsorption of acetone from cyclohexane on silica, alumina, coal, natural and leached chrysotile was investigated. Adsorption phenomenon was investigated by non-linear fitting, considering the Langmuir or Freundlich models. According to non-linear regression, coal present the highest K _L (12.07) and K _F (9.115) parameters. Silica and leached chrysotile exhibited similar behavior in terms of both K _L and K _F parameters. Alumina presented the highest adsorption capacity according to both Langmuir (q _m =58.689) and Freundlich (1/n=0.844) models. Non-supported Ziegler-Natta catalyst systems were shown to be more sensitive to acetone contamination. For the polymerization reactions carried on with contaminated solvent after the percolation through the adsorbents, good results were observed in the case of silica and alumina. Coal was not suitable for use in this catalyst system, probably due to leaching of organic components by the solvent (cyclohexane).     

Concentration dependences of the physicochemical properties of a water–acetone system

Concentration dependences of the UV spectrum, refractive index, specific electrical conductivity, boiling point, pH, surface tension, and heats of dissolution of a water–acetone system on the amount of acetone in the water are studied. It is found that the reversible protolytic interaction of the components occurs in all such solutions, resulting in the formation of hydroxyl and acetonium ions. It is shown that shifts of the equilibrium between the molecules and ions in the solution leads to extreme changes in their electrical properties. It is concluded that the formation of acetone solutions of water is accompanied by heat absorption, while the formation of aqueous solutions of acetone is accompanied by heat release.     

Direct asymmetric aldol reaction of acetone with α-ketoesters catalyzed by primary-tertiary diamine organocatalysts

Novel primary-tertiary diamine organocatalysts derived from l-serine were utilized to promote enantioselective aldol reaction of acetone with α-ketoesters. The desired products were obtained in high yields and with good to excellent enantioselectivities (up to 95% ee).     

Synthesis of azamacrocyclic compounds by cyclocondensation of aliphatic α,ω-diamines with acetone

Cyclocondensation of 1,4-diaminobutane and 1,6-diaminohexane with acetone afforded the corresponding 18- and 22-membered trans-azamacrocyclic Curtis compounds in high yield, which contain two azomethine and amine nitrogen atoms. A complex mixture of the products formed containing less than 25% of 16-membered azamacrocyclic cis- and trans-isomers when reacting 1,3-diaminopropane with acetone.     

Facile synthesis of mesoporous silica nanoparticles with controlled morphologies using water–acetone media

Mesoporous silica nanoparticles with controlled morphologies including nanococoons, nanorods and nanospheres have been synthesized in water–acetone media at room temperature using cetyltrimethylammonium bromide (CTAB) as the template. The obtained nanoparticles generally show hexagonal-like mesoporous structures with average pore size ranging from 2.7 to 3.3 nm and surface area from 806 to 1055 m²/g, respectively. It was found that the changes in water-to-acetone molar ratios have a dramatic impact on the morphologies of the mesoporous silica with different surface roughness, probably due to the solvent influence on the rate of the hydrolysis of tetraethoxy silane (TEOS) and the polymerization of inorganic species. Interestingly, the morphology of the mesoporous silica products can be controlled in shape from nanococoons to nanorods to nanospheres just by decreasing the water-to-acetone molar ratio from 75 to 30 to 15, respectively. From transmission electron microscopy (TEM) images, it was observed that mesoporous parallel channels run along the short axis in some areas in the nanorods, whereas the radially arranged mesopore channels are present in the nanospheres. Additionally, hydrothermal treatment leads to rougher surfaces while retaining the morphologies and nanostructures of these mesoporous silicas.     

Effect of epoxidation of natural rubber on the pervaporation separation of acetone–chlorinated hydrocarbon mixtures

The pervaporation separation and the swelling behavior of chlorinated hydrocarbon/acetone mixtures were investigated using natural rubber (NR) and epoxidized natural rubber (ENR) membrane with 25 and 50 mol% epoxidation, respectively. The swelling degree increases with increase in the epoxidation level. The flux and separation factor of the membranes were determined both as a function of mole percent epoxidation and of the feed mixture composition. The membranes were found to be permselective to chlorinated hydrocarbons from acetone–chlorinated hydrocarbon mixtures. The flux decreases with increase in epoxidation level, whereas the separation factor increases. The permeation decreases and separation factor increases with increase in the acetone feed concentration. The availability of raw materials, low cost of implementation and easy processability of the system makes this method of separation highly applicable and recommendable.     

Synthesis of β-octabromocalix[4]pyrroles and conformational diversity in their acetone inclusion complexes

Two β-octabromocalix[4]pyrroles were synthesized using a modified strategy, which provides the advantage of large scale preparation with rapid purification. The acetone inclusion complexes of these compounds show different structural orientations featuring diverse types of novel hydrogen bonding owing to varied meso-substitution along with the presence of eight peripheral bromine atoms.     

Ab initio study of mechanism of cycloaddition reaction between H2Ge = Ge: and acetone

The mechanism of the cycloaddition reaction between singlet H₂Ge = Ge: and acetone has been investigated with CCSD(T)//MP2/6-31G* method. From the potential energy profile, it could be predicted that the reaction has two competitive dominant reaction pathways. The reaction rule presented is that the two reactants firstly form a four-membered Ge-heterocyclic ring germylene through the [2 + 2] cycloaddition reaction. Because of the 4p-unoccupied orbital of Ge atom in the four-membered Ge-heterocyclic ring germylene and the π-orbital of acetone forming a π → p donor–acceptor bond, the four-membered Ge-heterocyclic ring germylene further combines with acetone to form an intermediate. Because the Ge atom in intermediate happens sp³ hybridization after transition state, then, intermediate isomerizes to a spiro-Ge-heterocyclic ring compound via a transition state. Simultaneously, the ring strain of the four-membered Ge-heterocyclic ring germylene makes it isomerize to a twisted four-membered ring product.     

Separation of acetone/water mixtures by a modified γ-alumina membrane via a new method

A new surface deposition method was researched to decrease pore size of ceramic membranes. CaCO₃ was chosen to modify the top layer of γ-alumina membranes prepared by sol–gel processes. Separation of gaseous acetone/water mixtures by vapor permeation was carried out to characterize the membranes. Improvement of membrane separation property after modifications and SEM photographs proved that this new method was effective to reduce the membrane pore size.     

Rhodium-catalyzed tandem aldol condensation–Robinson annulation between aldehydes and acetone: synthesis of 3-methylcyclohexenones

A simple catalytic, redox-neutral access to 3-methylcyclohexenones has been developed via rhodium catalysis in the presence of an amine additive and Ag₂CO₃. This process utilized simple aldehydes and acetone as substrates and tolerates a variety of functional groups. Disubstituted phenols were isolated in moderate yields when Cu(OAc)₂ was employed as an oxidant.     

Highly enantioselective and efficient organocatalytic aldol reaction of acetone and β,γ-unsaturated α-keto ester

An effective organocatalytic asymmetric aldol reaction of acetone to β,γ-unsaturated α-keto ester has been developed. In the presence of 5 mol % of 9-amino (9-deoxy)-epicinchona alkaloid and 10 mol % of 4-nitrobenzoic acid, the aldol adducts containing a chiral tertiary alcohol moiety were obtained in excellent yields and enantioselectivities.     

Spectral shift of the n → π* transition for acetone and formic acid with an explicit solvent model

In our recent work, a new form of the electrostatic solvation energy for the nonequilibrium polarization has been derived by introducing the method of constrained equilibrium state in the framework of continuous medium theory. Up until now, the idea of the constrained equilibrium state method has not been introduced into the explicit solvent model by others; therefore this nonequilibrium energy form was further equivalently extended to the explicit solvent model in this work based on the discrete representation of the solvent permanent charges and induced dipoles. Making use of this expression in explicit solvent model, we modified the nonequilibrium module in the averaged solvent electrostatic potential/molecular dynamics program to implement numerical calculations. Subsequently, the new codes were applied to study the solvatochromic shifts of the n → π* absorption spectra for acetone and trans-formic acid in aqueous solution. The calculation results show a good agreement with the experimental observations. When our results of spectral shift are compared with those achieved directly from the continuum model, it can be seen that both the explicit solvent model and continuum model derived based on the constrained equilibrium approach can give reasonable predictions. The hydrogen bond effect was also discussed and deemed to be a dominant contribution to the spectral shift by calculating the n → π* absorption spectra of acetone-water complexes.     

Surface tension isotherms of the dioxane–acetone–water and glycerol–ethanol–water ternary systems

The results of the experimental and theoretical studies of the concentration dependence of surface tension of aqueous solutions of the 1,4-dioxane–acetone–water and glycerol–ethanol–water ternary systems were given. The studies were performed by the hanging-drop method on a DSA100 tensiometer. The maximum error of surface tension was 1%. The theoretical models for calculating the surface tension of the ternary systems of organic solutions were analyzed.     

Adsorption of reaction components from propene oxidation to acetone on Sn?Mo?Ox catalysts

The adsorption of water, propene and acetone was carried out on Sn–Mo–O_x catalysts with different atomic ratios Mo/Mo+Sn. The number of active sites for adsorption of water, acetone and propene was found to go through a maximum at a molybdenum content of 15–20 at. %.

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, Sn–Mo–O_x Mo/Mo+Sn. , , 15–20 . %.