1,721,098 research outputs found
Influenza del tipo di confezione sulla conservazione del patrimonio vitaminico e delle proprietà organolettiche del latte
No full textla ricerca è stata condotta utilizzando un lotto di latte pastorizato di alta qualità, confezionato parte in Tetra Brik, parte in Tetra Rex e parte in bottiglie PET. Dai risultati ottenuti risulta evidente che riducendo l'impatto della luce, attraverso l'impiego di un materiale di confezionamento reso opaco alle radiazioni luminose, o di un multistrato a base cartoncino Tetra Pak, è possibile preservare il patrimonio vitaminico in modo pressochè completo e di conseguenza l'intero suo valore nutrizionale
Fe-0 initiated halogen atom transfer radical addition of methyl 2-Br-2-Cl-carboxylates to olefins
No full textThe halogen atom transfer radical addition (HATRA) of methyl 2-Br-2-Cl-carboxylates to alkenes is obtained in good yields by catalytic amounts of iron filings in dimethylformamide/1,2-dichloroethane at 80 degrees C under argon
Oxidation of nitrobenzene, chlorobenzenes and chlorophenols using liquid-phase ruthenium catalysts
No full textRuthenium trichloride and various ruthenium(II) complexes, such as [Ru(H2O)(2) (L)(4)](BF4)(2) and [RuCl2(L)(4)] (L=DMSO), are effective catalysts for the complete oxidation of substituted aromatics at ambient temperature and in the liquid phase (double phase or water with suitable amounts of a surfactant agent) in the presence of an oxidizing agent, preferably monopersulfate. The oxidation of benzoic acid, chloro-, bromo-, iodo- and nitrobenzene and a number of polychlorobenzenes and polychlorophenols was followed by monitoring the nature and the relative amounts of the final products; chlorinated substrates are mainly converted into hydrochloric acid and carbon dioxide. Factors such as solvent, substrate, oxidant and concentration affect the reactions. The most favorable reaction conditions require the presence of polar media, like nitromethane or water. The fate of the catalyst during the various stages of the reactions was followed, which gave indications of the nature of the active species involved. The overall results imply that a strongly oxidizing ruthenium derivative is responsible for the effective oxidation with monopersulfate, tentatively a highly reactive peroxoruthenium species [Ru-O-O-SO3H]. Oxidation of chlorobenzene is first order in both the substrate and the catalysts and an n (or inverse) kinetic isotope effect is measured. The rates of the oxidation of mono-substituted benzenes depend upon the degree of deactivation of the aromatic ring, thus suggesting an initial electrophilic attack followed by a series of faster steps. Phenol and polychlorophenols are more sensitive to oxidation than substituted benzenes
Stereoselective Dehydrobromination of alkyl alpha-Br-alpha-Cl-carboxylates
No full text(Z)-Alkyl alpha-Cl-alpha,beta-unsaturated esters are prepared in excellent yields by stereoselective dehydrobromination of alkyl alpha-Br-alpha-Cl-carboxylates with LiCl-Li2CO3 in dimethylformamide
Coordination behavior of N-protected amino acids. Structural and spectroscopic study of complexes of CoII, NiII and CuII with N-(4-aminobenzoyl)glicine
No full textThe structural and spectroscopic properties of complexes of N-(4-aminobenzoyl)glycine (HL) with Co(II), Ni(II) and Cu(II) have been investigated. The complex [{CoL2(H2O)2}n].2nH2O crystallizes in the space group P1BAR, with a = 8.027(2), b = 8.031(2), c = 10.033(1) angstrom, alpha = 96.52(2)degrees, beta = 100.17(2)degrees, gamma = 119.19(2)degrees and Z = 1; the nickel(II) homologue is isomorphous. The complex [(CuL2)n].4nH2O crystallizes in the space group P2(1)/n, with a = 4.673(1), b = 20.476(1), c = 12.026(1) angstrom, beta = 97.38(2)degrees and Z = 2. The cobalt(II) co-ordination geometry is tetragonally distorted octahedral with four oxygens from two water molecules and two carboxylate groups in the basal plane and two amino nitrogens in the apical position. The copper(II) complex shows a strongly distorted tetragonal-octahedral geometry with two oxygens and two amino nitrogens of different amino acidate anions in the basal plane and two oxygens in the off-z-axis position. The ligand acts as bidentate bridging giving rise to a polymeric one-dimensional chain in the cobalt(II) complex and two-dimensional layers in the copper(II) one
Ferrocene promoted addition of methyl 2,2-dichloro-carboxylates to 1-alkenes
No full textThe Kharasch addition of methyl 2,2-dichlorocarboxylates to 1-alkenes is promoted by ferrocene in DMF at 100 degrees C, affording 1:1 adducts in satisfactory yields
The CuBr/Fe promoted olefin alkylation of 2-Br-2-Cl-carboxylate methyl esters
No full textMethyl 2-Br-2-Cl-carboxylates react with 1-octene in DMF/CH2Cl2 in a radical process promoted by CuBr/Fe, yielding 2-alkyl-2-Cl-4-Br-carboxylates smoothly and efficiently
Acetals by AlFe-pillared montmorillonite catalysis
No full textAlFe-pillared montmorillonite is an efficient catalyst for acetals preparation in CH2Cl2 at room temperatur
A tuning point in plant acoustics investigation
No full textIn a very recent book called Sensory Biology of Plants, published by renowned publisher Springer Nature, the authors stated that the scientific literature gathered so far regarding knowledge around the field of Plant Acoustics allows us to divert the focus from the question "whether plants perceive sound" toward the questions "how and why they are doing it" Some phenomena are well known: roots perceive the sound of flowing water and display a sound-mediated growth toward the water source, while the buzz pollination process allows plants to minimize the pollen lost and maximize which is collected by true pollinators. But plants are far more perceptive and responsive to their environment than we generally consider them to be, and they are communicating far more information than we realize if we only took all their signals (VOCs, sound, exudates, etc.) into a greater picture. Could Volatile Organic Compounds (VOCs) be involved in mediating more responses than we imagine? VOC synthesis and release is known to be elicited also by electrical signals caused by mechanical stimuli, touching and wounding being among these, serving as info-chemicals in the communication between plants ("eavesdropping"), and within the organs of the same plant, in order for it to get synchronized with its surroundings. This paper is an overview of the discoveries around plant perception with a focus on the link between mechanical stimuli, as sound vibrations are, and changes in plant physiology leading to VOC emission
Mechanism of Inactivation of Prostaglandin H2 Synthase 1 (PGH2S-1) by Resveratrol and its Analogs
No full text3,4',5-Trihydroxy-trans-stilbene (resveratrol) is a natural product derived from grapes that has anti-inflammatory, anti-coagulation, and cancer chemopreventive properties. It inhibits both the cyclooxygenase (cox) and peroxidase (perox) activities of Prostaglandin H2 Synthase 1 (PGH2S-1). Resveratrol was rapidly oxidized by the perox activity, but unlike other co-reductants inactivated both enzyme activities. The irreversible loss of cox and perox activity was accompanied by the oxidation of resveratrol to yield the inactivator and had an absolute requirement for a peroxide substrate. Resveratrol represents a new class of inhibitors for PGH2S-1 that inactivate both the cox and perox activities of the enzyme, but require catalytic activation to exert their effects. Perox inhibitors are attractive because catalytic intermediates formed in the perox reaction are potent oxidants, which can generate reactive species that can damage biological macromolecules
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