Search results for " aroma"
showing 10 items of 370 documents
Evolution of olfactory responses in the first two years of life : effect of early exposures and link with food behaviour
2013
The role of taste on food preferences has already been investigated, however, little is known about the role of olfaction. The main objectives of this work were to assess infants’ olfactory responses, their dynamic during the first two years of life, and also their links with early food exposures, food liking and infants’ food neophobia. This work was conducted within a longitudinal study named OPALINE (Observatory of food preferences in infants and children). Olfactory responses were assessed, in 8-, 12- and 22-month-old infants, towards pleasant odours, such as vanilla, and unpleasant odours, such as fish. The results reveal that, from 8 months, infants can discriminate pleasant and unple…
Are one-step aromatic nucleophilic substitutions of non-activated benzenes concerted processes?
2019
Aromatic nucleophilic substitution (SNAr) reactions of non-electrophilically activated benzenes have been studied within the Molecular Electron Density Theory (MEDT) at the B3LYP/6-311+G(d) computational level. These reactions, taking place through a one-step mechanism, present a high activation Gibbs free energy, ΔG≠ = 31.0 kcal mol-1, which decreases to 22.1 kcal mol-1 in the intramolecular process. A topological analysis of the electron localisation function along the reaction paths permits establishing the non-concerted nature of these SNAr reactions. A series of unstable structures, with similar electronic structures to those of Meisenheimer intermediates, are characterised. The presen…
Biomimetic oxidation of pyrene and related aromatic hydrocarbons. Unexpected electron accepting abilities of pyrenequinones
2014
We present a mild catalytic method to oxidize PAHs and, in particular, pyrene. The pyrenediones are much better electron acceptors than benzoquinone in the gas phase and present similar accepting abilities in solution.
Chapter 9 The electrophilicity index in organic chemistry
2007
Abstract We review in this chapter the applications of theoretical scales of global and local electrophilicity to rationalize the reactivity and selectivity for a significant number of reactions in organic chemistry. The model is based on the global electrophilicity index, formerly introduced by Maynard et al. and further formalized by Parr et al. The global electrophilicity index categorizes, within a unique absolute scale, the propensity of electron acceptors to acquire additional electronic charge from the environment. The local extension of this index provides useful information about the active sites of electrophiles, thereby allowing the characterization of the intramolecular selectiv…
The toxicity and concentrations of PAHs in creosote-contaminated lake sediment
1999
Sediment samplers, divided into three layers (0 – 10, 10 – 20 and 20 – 30 cm), were collected from 16 sites in Lake Jamsanvesi, Central Finland. The acute toxicity of pore waters and elutriates (sediment + water 1:4 v/v) were studied by bioluminescence inhibition test and by immobilisation of water fleas (Daphnia magna Straus). Concentrations of polycyclic aromatic hydrocarbons (PAHs) in sediments and elutriates were measured by gas chromatography using flame ionization detection (GC/FID). The highest total PAH concentration was 3.3 mg/g dry weight in the sediment and up to 1.7 mg/l in the elutriate of the uppermost (0 – 10 cm) layer, also being the most toxic to photoluminencent bacteria, …
Levels, fingerprint and daily intake of polycyclic aromatic hydrocarbons (PAHs) in bread baked using wood as fuel
2009
Concentrations, fingerprint and daily intake of 16 PAHs in 15 bread samples baked using wood as fuel are examined in this work. Analysis was performed by GC/MS after saponification of the samples and clean up of the extract. The total concentration of the 16 analytes varies from 6 to 230 microg/kg on dry weight (d.w.). The better extraction procedure was estimated by analyzing test-samples and using different extraction methods. Additionally, for every analyzed sample, the extraction yield has been determined by the use of surrogate standards. Extraction yields were never less than 77% and in most cases almost 100%. The profiles of PAHs (percentage) are similar for all the analyzed samples …
Chlorinated dioxins and dibenzothiophenes in fly ash samples from combustion of peat, wood chips, refuse derived fuels and liquid packaging boards
1995
Abstract Peat, wood chips, refuse derived fuel and liquid packaging board in different combinations were burned at a temperature of at least 850 °C. Fly ash samples from these combustions were analyzed for polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzothiophenes (PCDBTs) by high resolution GC/MS. The concentrations of tri- and tetrachlorodibenzothiophenes and tri-, tetra- and pentachlorodioxins were highest when mixtures of wood chips and refuse derived fuel (RDF) were burned. The fly ash from the combustion of pure peat pellets did not contain any polychlorinated dibenzothiophenes. When wood chips and RDF were burned the concentrations of chlorinated compounds in fly…
Biochar based remediation of water and soil contaminated by phenanthrene and pentachlorophenol
2017
Abstract Phenanthrene (Phe) and pentachlorophenol (PCP) are classified as persistent organic pollutants and represent serious concern for the environment as they are toxic and ubiquitous. Biochar based remediation is an emerging technology used in water and soil contamination. In this study we used poplar (BP) and conifer (BC) biochars to remediate water and soil contaminated by Phe and PCP. BP and BC were able to remove completely either Phe or PCP from contaminated water within one to three days. When biochar was confined in a porous membrane, BC and BP maintained their sorption efficiency for several remediation cycles. However, in these conditions BC allowed faster Phe removal. In soil …
Design, characterization and comparison of materials based on β and γ cyclodextrin covalently connected to microporous silica for environmental analy…
2018
Abstract Determination of organic pollutants in environmental samples presents great difficulties due to the lack of sensitivity and selectivity in many of the existing analytical methods. In this work, the efficiency of materials based on silica structures containing bounded γ-cyclodextrin has been evaluated to determinate phenolic compounds and polycyclic aromatic hydrocarbons in air and water samples, respectively, in comparison with materials made of β-cyclodextrin. According to the results obtained for the material characterization, the new γ-cyclodextrin solid phase does not apparently present any porosity when used in air samples, but it has been shown to work efficiently for the pre…
Phytoremediation of polyaromatic hydrocarbons, anilines and phenols
2002
International audience; Phytoremediation technologies based on the combined action of plants and the microbial communities that they support within the rhizosphere hold promise in the remediation of land and waterways contaminated with hydrocarbons but they have not yet been adopted in large-scale remediation strategies. In this review plant and microbial degradative capacities, viewed as a continuum, have been dissected in order to identify where bottle-necks and limitations exist. Phenols, anilines and polyaromatic hydrocarbons (PAHs) were selected as the target classes of molecule for consideration, in part because of their common patterns of distribution, but also because of the urgent …