Search results for " reactivity"

New insights in chemical reactivity from quantum chemical topology.

2021

International audience; Based on the quantum chemical topology of the modified electron localization function ELFx, an efficient and robust mechanistic methodology designed to identify the favorable reaction pathway between two reactants is proposed. We first recall and reshape how the supermolecular interaction energy can be evaluated from only three distinct terms, namely the intermolecular coulomb energy, the intermolecular exchange‐correlation energy and the intramolecular energies of reactants. Thereafter, we show that the reactivity between the reactants is driven by the first‐order variation in the coulomb intermolecular energy defined in terms of the response to changes in the numbe…

Unravelling [3+2] Cycloaddition Reactions through the Molecular Electron Density Theory

2018

Después de la primera clasificación de las reacciones 32CA en reacciones de tipo zw y pr, establecidas en el año 2014, la estructura y reactividad de los TACs más importantes utilizados en las reacciones 32CA ha sido completamente caracterizado en base a la MEDT propuesta recientemente. Entre la gran cantidad de trabajo desarrollado a lo largo de la presente tesis doctoral, se han seleccionado y discutido ocho publicaciones representativas, que permitieron caracterizar dos nuevos tipos de reactividad y consolidar la reactividad original de tipo zw. Así, dependiendo de las cuatro estructuras electrónicas diferentes de los TACs, es decir, pseudodiradical, pseudoradical, carbenoide y zwitterió…

Initial stages of metal oxides thin films growth by MOCVD: physicochemical characterisation of the film/substrate interface

2006

The initial stages of Metalorganic Chemical Vapour Deposition (MOCVD) of TiO2 thin films on Si(100) were studied in situ by surface analyses (XPS, ARXPS, AES). An original experimental set-up was built for this purpose and developed. Information obtained from these in situ experiments was completed by ex situ characterisations (HRTEM, SIMS, GIXRD...).The formation of an interfacial SiOy<2 layer resulting of the interaction of the precursor Ti(OCH(CH3)2)4 with the substrate takes place before the formation of stoichiometric TiO2 and leads to the presence of carbon at the interface. At the deposition temperature, 675 °C, silicon diffusion within the TiO2 external layer was also revealed. Conc…

Fabrication and characterization of barium silicate ultrathin films as an alternative gate oxide

2008

Down-scaling of elementary CMOS elements requires the replacement of SiO2 as a gate oxide. By the identification of the formation conditions of barium silicate in direct contact of a silicon substrate, this study revealed a potential candidate. First of all, a reaction between Ba and SiO2 leading to the formation of barium silicate as been evidenced by in-situ XPS and SR-PES analyses. Then, barium silicate films have been elaborated by oxygen and barium co-deposition at 580 °C. Thermal treatments under vacuum showed that barium silicate was thermally stable up to 900 °C. TEM and SIMS ex-situ analyses revealed a sharp interface with the substrate. Finally, an experimental setup dedicated to …

Are hedonic responses to food odours linked to food liking in infants at 12 and 22 months?

2013

Communication orale (résumé 1 p.) ; http://www.pangborn2013.com/; International audience

Photochemistry of oxidized Hg(I) and Hg(II) species suggests missing mercury oxidation in the troposphere.

2020

8 pags., 5 figs., 2 tabs.

New oxygenated eudesmanolides from artemisia herba-alba

1990

Abstract The aerial parts of Artemisia herba-alba Asso subsp.valentina Lam. (Asteraceae) yielded the new eudesmanolides 1-11 and the new sesquiterpene-monoterpene adducts 12-13. The absolute configuration of compound 6 was confirmed with the aid of X-ray diffraction analysis. Some aspects of the thermal and photochemical reactivity of 2,4-cyclohexadienones are discussed.

Photochemical Functionalization of Allyl Benzoates by C-H Insertion

2013

The photoreactivity of allyl benzoates, containing an electron-rich double bond, has been explored by irradiation at 305 nm in different solvents. Solvent addition products arising from an insertion of the alpha H–C bonds of THF, dioxane, and i-PrOH to the allylic double bond was realized. The observed reactivity depended on reaction conditions and substitution pattern of the substrate. A DFT study on this unusual reaction was performed allowing the formulation of two mechanistic pathways.

1972

Photochemical reactivity of 6α-hydroxy, 7-keto neoclerodane diterpenoids

2006

Abstract The photochemical reactivity, in methanol at λ  = 254 nm, of two 6α-hydroxy-7-keto neoclerodane, isoeriocephalin ( 1 ) and teucrolivin B ( 2 ) was evaluated. From the first compound, two new products were obtained: the 6β-hydroxy epimer ( 3 ) and the ɛ-lactone ( 4 ). The second one yielded exclusively the new spiro γ-lactone ( 5 ). The formation of these new products can be explained by the well-known radical mechanism Norrish type I.