Mitigation of the inhibitory effects of co-existing substances on the Fenton process by UV light irradiation.

Co-existing substances (substances not targeted for degradation) can negatively affect wastewater treatment process performance. Here, we quantitatively evaluated the effects of propanal, a common co-existing substance, on the degradation of the azo-dye Orange II, a common pollutant, by the Fenton process to provide data for the development of measures to reduce the effects of co-existing substances on this wastewater treatment process. Inhibition rate (IR; ratio of the reaction rate constants obtained in the absence and presence of propanal) was calculated to examine the effects of propanal on the degradation of Orange II. The IRs for the Fenton process in the first phase and the second phase were 1.6 and 4.2, respectively. However, addition of ultraviolet irradiation to the Fenton process (i.e., the photo-Fenton process) resulted in a comparable IR for the first phase but a markedly lower IR for the second phase. We attributed this to the improvement of the photo-reduction reaction rate due to complexation of propanal with ferric ions, which compensated for the scavenger effects (the trapping of OH radicals) of propanal. Thus, ultraviolet irradiation reduced the inhibitory effects of propanal on the degradation of Orange II by the Fenton process.

UV-C suppression on hazardous metabolites in Microcystis aeruginosa: Unsynchronized production of microcystins and odorous compounds at population and single-cell level.

The effectiveness of UV-C towards the toxin and odor of M. aeruginosa at population and single cell levels were investigated in three ways. In the absence of UV-C, MC-LR and ß-cyclocitral production show similar pattern of incremental rate with growth rate on population level shown as intracellular concentrations of MC-LR (CMC) and ß-cyclocitral (CBCC), but the cellular quota of MC-LR (QMC) and ß-cyclocitral (QBCC) at single-cell level reached the maximum values, 37.5 ± 1.2 fg cell-1 and 4.3 ± 0.1 fg cell-1, just after the early exponential phase. Second, upon UV-C irradiation, the CMC consistently decreased by 10-41% with increase of UV-C dosage (50-200 mJ cm-2) while CBCC increased by 2-14%. Third, during the 14 days' post-UV incubation, UV-C at 75-200 mJ cm-2 induced remarkable suppressing effects on both CMC and CBCC for 3-14 days. The suppressing effects on QMC and QBCC were induced by UV-C at 100 mJ cm-2 and above, with shorter suppressing periods by 1-4 days and lower decremental rates by 21%-30% than that of CMC and CBCC, indicating interruptions on biosynthesis processes partially contribute to suppression effects of CMC and CBCC. The suppression effect on either CBCC or QBCC, with higher decrement rates while lower recovery rates, was more severe than CMC and QMC.

Characterization of the Aldehydes and Their Transformations Induced by UV Irradiation and Air Exposure of White Guanxi Honey Pummelo (Citrus Grandis (L.) Osbeck) Essential Oil.

Aldehydes are key aroma contributors of citrus essential oils. White Guanxi honey pummelo essential oil (WPEO) was investigated in its aldehyde constituents and their transformations induced by UV irradiation and air exposure by GC-MS, GC-O, and sensory evaluation. Nine aldehydes, i.e., octanal, nonanal, citronellal, decanal, trans-citral, cis-citral, perilla aldehyde, dodecanal, and dodecenal, were detected in WPEO. After treatment, the content of citronellal increased, but the concentrations of other aldehydes decreased. The aliphatic aldehydes were transformed to organic acids. Citral was transformed to neric acid, geranic acid, and cyclocitral. Aldehyde transformation caused a remarkable decrease in the minty, herbaceous, and lemon notes of WPEO. In fresh WPEO, ß-myrcene, d-limonene, octanal, decanal, cis-citral, trans-citral, and dodecenal had the highest odor dilution folds. After the treatment, the dilution folds of decanal, cis-citral, trans-citral, and dodecenal decreased dramatically. This result provides information for the production and storage of aldehyde-containing products.

Portable photocatalytic air cleaners: efficiencies and by-product generation.

Portable photocatalytic air cleaners were investigated in 24 and 48 m(3) emission test chambers with regard to efficiency and by-product generation. For this purpose, formaldehyde, decane, 1,2-dichlorobenzene, toluene, α-pinene and heptanal were doped at sub-ppm concentration levels into the chambers individually and in mixtures. By way of specified test protocols, efficiencies could be distinguished but were strongly dependant on the choice of test compounds, especially on whether single or multi compound dosing was used, and on long-term effects. Initial clean air delivery rates (CADRs) up to 137 m(3)/h were measured. Typical by-products were found in significant concentrations. The main ones were formaldehyde up to 50 ppb (62 µg/m(3)) and acetone up to 80 ppb (190 µg/m(3)). Other aldehydes were also found, but at smaller levels. The detection of chloroacetone, a strong irritating compound, at concentrations up to 15 ppb (57 µg/m(3)) strengthens the importance of such investigations especially in cases were chloro-organic compounds are involved.

Attenuated UV Radiation Alters Volatile Profile in Cabernet Sauvignon Grapes under Field Conditions.

This study aimed to explore the effect of attenuated UV radiation around grape clusters on the volatile profile of Cabernet Sauvignon grapes (Vitis vinifera L. cv.) under field conditions. Grape bunches were wrapped with two types of polyester films that cut off 89% (film A) and 99% (film B) invisible sunlight of less than 380 nm wavelength, respectively. Solar UV radiation reaching the grape berry surface was largely attenuated, and an increase in the concentrations of amino acid-derived benzenoid volatiles and fatty acid-derived esters was observed in the ripening grapes. Meanwhile, the attenuated UV radiation significantly reduced the concentrations of fatty acid-derived aldehydes and alcohols and isoprenoid-derived norisoprenoids. No significant impact was observed for terpenes. In most case, these positive or negative effects were stage-dependent. Reducing UV radiation from the onset of veraison to grape harvest, compared to the other stages, caused a larger alteration in the grape volatile profile. Partial Least Square Discriminant Analysis (PLS-DA) revealed that (E)-2-hexenal, 4-methyl benzaldehyde, 2-butoxyethyl acetate, (E)-2-heptenal, styrene, α-phenylethanol, and (Z)-3-hexen-1-ol acetate were affected most significantly by the attenuated UV radiation.

Pulsed corona discharge oxidation of aqueous lignin: decomposition and aldehydes formation.

Lignin is the mass waste product of pulp and paper industry mostly incinerated for energy recovery. Lignin is, however, a substantial source of raw material for derivatives currently produced in costly wet oxidation processes. The pulsed corona discharge (PCD) for the first time was applied to lignin oxidation aiming a cost-effective environmentally friendly lignin removal and transformation to aldehydes. The experimental research into treatment of coniferous kraft lignin aqueous solutions was undertaken to establish the dependence of lignin oxidation and aldehyde formation on the discharge parameters, initial concentration of lignin and gas phase composition. The rate and the energy efficiency of lignin oxidation increased with increasing oxygen concentration reaching up to 82 g kW-1 h-1 in 89% vol. oxygen. Oxidation energy efficiency in PCD treatment exceeds the one for conventional ozonation by the factor of two under the experimental conditions. Oxidation at low oxygen concentrations showed a tendency of the increasing aldehydes and glyoxylic acid formation yield.

Ultrasound-assisted phase-transfer catalysis method in an aqueous medium to promote the Knoevenagel reaction: advantages over the conventional and microwave-assisted solvent-free/catalyst-free method.

Given the broad spectrum of uses of acrylonitrile derivatives as fluorescent probes, AChE inhibitors, and others, it is necessary to find easy, efficient and simple methods to synthesize and diversify these compounds. We report the results of a comparative study of the effects of three techniques on the reactions between heterocyclic aldehydes and 2-(benzo[d]thiazol-2-yl)acetonitrile: stirring; ultrasound coupled to PTC conditions (US-PTC); and MW irradiation (MWI) under solvent and catalyst-free conditions. The effects of conditions on reaction parameters were evaluated and compared in terms of reaction time, yield, purity and outcomes. The US-PTC method is more efficient than the MWI and conventional methods. The reaction times were considerably shorter, with high yields (>90%) and good levels of purity. In addition, X-ray diffraction analysis and quantum mechanical calculations, at the level of density functional theory (DFT), ratify obtaining acrylonitrile isomers with E configurations. The crystal structure of 3c is stabilized by weak C-Ho⋯N intermolecular interactions (Ho⋯NC=2.45 Å, Co⋯NC=3.348(3) Å, Ho⋯NC=162°), forming centrosymmetric ring R2(2) (20) along the crystallographic a axis.

Volatile organic compounds characterized from grapevine (Vitis vinifera L. cv. Malbec) berries increase at pre-harvest and in response to UV-B radiation.

Ultraviolet-B solar radiation (UV-B) is an environmental signal with biological effects in plant tissues. Recent investigations have assigned a protective role of volatile organic compounds (VOCs) in plant tissues submitted to biotic and abiotic stresses. This study investigated VOCs in berries at three developmental stages (veraison, pre-harvest and harvest) of Vitis vinifera L. cv. Malbec exposed (or not) to UV-B both, in in vitro and field experiments. By Head Space-Solid Phase Micro Extraction-Gas Chromatography-Electron Impact Mass Spectrometry (HS-SPME-GC-EIMS) analysis, 10 VOCs were identified at all developmental stages: four monoterpenes, three aldehydes, two alcohols and one ketone. Monoterpenes increased at pre-harvest and in response to UV-B in both, in vitro and field conditions. UV-B also augmented levels of some aldehydes, alcohols and ketones. These results along with others from the literature suggest that UV-B induce grape berries to produce VOCs (mainly monoterpenes) that protect the tissues from UV-B itself and other abiotic and biotic stresses, and could affect the wine flavor. Higher emission of monoterpenes was observed in the field experiments as compared in vitro, suggesting the UV-B/PAR ratio is not a signal in itself.

A convenient and efficient protocol for the synthesis of acylals catalyzed by Brønsted acidic ionic liquids under ultrasonic irradiation.

The synthesis of acylals (1,1-diacetates) via the reactions of aldehydes with acetic anhydride was carried out in 85-97% yields at room temperature under ultrasound irradiation catalyzed by the Brønsted acidic ionic liquid [bmpy]HSO(4). This method provides several advantages, such as solvent-free conditions, operational simplicity, higher yields, and reduced environmental consequences. The ionic liquid was recovered and reused.

Rapid and efficient synthesis of fused heterocyclic pyrimidines under ultrasonic irradiation.

Some fused heterocyclic pyrimidines have been synthesized in high yields using ultrasound irradiation in a one-pot, three-component and efficient process by condensation reaction of barbituric acids, aldehydes and a series of enamines in water. Prominent among the advantages of this new method are operational simplicity, good yields in short reaction times and easy work-up procedures employed.

The allylation reactions of aromatic aldehydes and ketones with tin dichloride in water.

The allylation reactions of aromatic aldehydes and ketones were carried out in 31-86% yield using SnCl(2)-H(2)O system under ultrasound irradiation at r.t. for 5h. The reactions in the same system gave homoallyl alcohols in 21-84% yield with stirring at r.t. for 24h. Compared with traditional stirring methods, ultrasonic irradiation is more convenient and efficient.

Microwave enabled umpulong mechanism based rapid and efficient four- and six-component domino formations of 2-(2'-azaaryl)imidazoles and anti-1,2-diarylethylbenzamides.

Concise and efficient six-component and four-component domino approaches to anti-1,2-diarylethylbenzamides and highly substituted 2-(2'-azaaryl)imidazoles have been developed under solvent-free and microwave-irradiation conditions. The reactions showed a broad scope of substrates in which a wide range of common commercial aromatic aldehydes and heteroaryl nitriles can be used. The syntheses were finished within short periods (15-34 min) with good to excellent chemical yields and stereoselectivity that avoided tedious workup isolations. New mechanisms involving an umpolung have been proposed for these two reaction processes.

Acceleration of arylzinc formation and its enantioselective addition to aldehydes by microwave irradiation and aziridine-2-methanol catalysts.

The formation and 2-amino alcohol catalyzed addition of arylzinc reagents from and with boronic acids, respectively, is drastically accelerated to a few minutes under microwave irradiation without loss of enantioselectivity (up to 98% ee). Of the amino acid derived catalysts tested, the conformationally restricted bulky substituted aziridine-2-methanols derived from serine show the best overall performance in the formation of diarylmethanols.

Diels-Alder cycloadditions by microwave-assisted, continuous flow organic synthesis (MACOS): the role of metal films in the flow tube.

Thin Pd films have been deposited on the inside of capillary-sized tubes through which compounds undergoing Diels-Alder reactions have been flowed while being heated with microwave irradiation; dramatic rate accelerations are observed in the presence of the film, which has been shown to play both a heating and catalytic role.

Microwave-assisted organocatalytic anomerization of alpha-C-glycosylmethyl aldehydes and ketones.

The use of l-proline (30 mol %) and MW irradiation (13 W) with cooling promotes in a few hours the almost quantitative anomerization of alpha-C-glycosylmethyl aldehydes into beta-isomers. An open-chain enamine-based mechanism is postulated for this transformation. The anomerization of alpha-ketones was instead achieved by the pyrrolidine/TFA couple and MW irradiation at 120 degrees C (enamine mechanism) and by DBU as Brønsted base (enolate mechanism).

Microwave assisted condensation reactions of 2-aryl hydrazonopropanals with nucleophilic reagents and dimethyl acetylenedicarboxylate.

The reaction of methyl ketones 1a-g with dimethylformamide dimethylacetal (DMFDMA) afforded the enaminones 2a-g, which were coupled with diazotized aromatic amines 3a,b to give the corresponding aryl hydrazones 6a-h. Condensation of compounds 6a-h with some aromatic heterocyclic amines afforded iminoarylhydrazones 9a-m. Enaminoazo compounds 12a,b could be obtained from condensation of 6c with secondary amines. The reaction of 6e,h with benzotriazolylacetone yielded 14a,b. Also, the reaction of 6a,b,d-f,h with glycine and hippuric acid in acetic anhydride afforded pyridazinone derivatives 17a-f. Synthesis of pyridazine carboxylic acid derivatives 22a,b from the reaction of 6b,e with dimethyl acetylenedicarboxylate (DMAD) in the presence of triphenylphosphine at room temperature is also reported. Most of these reactions were conducted under irradiation in a microwave oven in the absence of solvent in an attempt to improve the product yields and to reduce the reaction times.

Aerobic oxidation of benzyl- and allylic alcohols under visible light irradiation of a fluorescent lamp in the presence of catalytic iodine.

Benzyl alcohols and allylic alcohols were found to be oxidized to the corresponding aldehydes in the presence of a catalytic amount of iodine under irradiation of a fluorescent lamp.

Facile aerobic photo-oxidation of aldehydes in the presence of catalytic lithium bromide.

Aldehydes were found to be oxidized to the corresponding carboxylic acid in the presence of catalytic lithium bromide under photo-irradiation.

Photoelectron imaging of propanal by resonant multiphoton ionization via the 3s Rydberg state.

We report the conformationally- and vibrationally-selected photoelectron spectroscopy of propanal obtained by resonance-enhanced multiphoton ionization (REMPI) using photoelectron imaging. These photoelectron spectra, employing (2 + 1) ionization via the (n, 3s) Rydberg transitions in the range from 365 to 371 nm, confirm that there are two stable conformer origins in the lowest ionic state, the cis conformer with a co-planar CCCO geometry and a gauche conformer with a approximately 119 degrees CCCO dihedral angle. From ab initio calculations at the B3LYP/6-311++G** level, we find the gauche conformer is slightly more stable, with the energy difference between two conformers determined to be only 65 cm(-1). In our photoelectron spectra, the vertical ionization potential (IP) for the cis conformer of propanal was then determined to be 9.999 (+/-0.003) eV, while that of the gauche conformer of propanal was estimated to be 9.944 eV. A long vibrational progression in the in-plane CCCO deformation vibrational mode, v, for the cis conformer is systematically observed in all photoelectron spectra in which this mode is excited, suggesting that the geometry of the ground ionic state is significantly different from that of the 3s Rydberg state, particularly along the v(15) coordinates.

An efficient carbonyl-alkene metathesis of bicyclic oxetanes: photoinduced electron transfer reduction of the Paternò-Büchi adducts from 2,3-dihydrofuran and aromatic aldehydes.

The bicyclic oxetanes and resulting from photocycloaddition of aromatic aldehydes to 2,3-dihydrofuran, were efficiently cleaved by means of electron-transfer reduction, photoinduced by the electronically excited reductants 1-methoxynaphthalene (MN) and 2,7-dimethoxynaphthalene (DMN) in acetonitrile. The fluorescence quenching rates of DMN/MN by and were determined by static methods, the triplet quenching rates were determined by means of laser flash photolysis (LFP). The product analysis established a "photo-photo metathesis" where both cycloaddition and cycloreversion processes are induced by photochemical processes.