Studies towards the stereoselective electrophilic amination of carbanions

Filip SV. Studies towards the stereoselective electrophilic amination of carbanions. Bielefeld (Germany): Bielefeld University; 2002.A rapid development of novel and more efficient amination methods has been recorded during the past decade, mostly regarding the electrophilic amination. There are only few efficient methods for reagent-controlled stereoselective electrophilic amination compared to those based on chiral substrates or chiral catalysts. An effective stereoselective amination reagent allows greater method flexibility, due to the high availability of prochiral nucleophilic substrates. In the present work the reactivity of three types of enantiomerically pure electrophilic amination reagents (N-lithiated N-pinenyl hydroxylamines, [alpha]-chloronitroso camphor and mannofuranose derivatives, and 1-deoxy-2,3:5,6-di-O-isopropylidene-1-nitro-[alpha]-D-mannofuranose) towards carbon nucleophiles (enolates and allyl organometallic compounds) was investigated, with the aim to provide a valuable method for the stereoselective synthesis of [alpha]-amino ketones and [alpha]-amino acids

Evaluation of thermal and oxidative stability of three generations of phenolic based novel dendritic fuel and lubricant additives

Antioxidants, particularly those designed for use in hydrocarbon media, suffer from a variety of limitations including high volatility and poor solubility. Using 2,2-bis(hydroxymethyl)propionic acid as the branching unit, a series of novel dendrons featuring 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic ester chain ends have been synthesised to provide improved solubility of such hindered phenolic antioxidants. The thermal stability, assessed by thermogravimetric analysis, revealed that all the functionalised dendrons have enhanced thermal stability when compared to commercial antioxidants (BHT, Irganox L135 and Irganox L57). Antioxidant ability was evaluated using pressurised differential scanning calorimetry and when blended with a lubricant base oil, at 0.5% w/w, an increase in antioxidant performance was observed when compared to the commercial antioxidants

Synthesis, characterisation, and performance evaluation of tri-armed phenolic antioxidants

In this study, a series of core units (glycerol, triethanolamine and triisopropanolamine derivatives) were investigated for their use in tri-armed phenolic antioxidants. The antioxidant ability of these tri-armed phenolic compounds featuring different core units were then evaluated in a hydrocarbon lubricant using differential scanning calorimetry (DSC) and compared to the commercially available antioxidants Irganox L135 and Irganox L57. An impressive oxidation induction time of ca. 9-12 minutes was observed for the glycerol based antioxidants when compared to the commercial antioxidants (ca. 4-6 minutes), whereas in contrast in the case of triethanolamine and triisopropanolamine derived antioxidants, a solubilising unit was incorporated in order to provide appropriate solubility within the hydrocarbon medium and revealed an excellent oxidation induction time of ca. 11-12 minutes

Competitive Adsorption of a Multi-functional Amine and Phenol Surfactant with Ethanol on Hematite from Non-Aqueous Solution

Surfactants, which contain phenol and amine groups, are commonly used in industries to protect metallic surfaces, and their efficiency depends strongly on factors such as pressure and temperature, solvent properties, and the presence of other surfactants in the system. In this work, we present a molecular simulation study of the competitive adsorption between a multifunctional phenol and amine surfactant model and ethanol at the oil/solid interface formed between iso-octane and a model hematite (α-Fe2O3) slab. We show that the surfactant strongly adsorbs at the iso-octane/hematite interface in the absence of ethanol at moderate temperatures. As the concentration of ethanol is increased, the ethanol molecules compete effectively for the adsorption sites on the iron oxide surface. This competition drives the surfactant molecules to remain in the bulk solution, while ethanol forms ordered and strongly coordinated layers at the oil/solid interface, despite the well-known complete miscibility of ethanol in iso-octane in bulk under standard conditions. Potential of mean force calculations show that the free energy of adsorption of the surfactant is approximately two times larger than that for a single ethanol molecule, but the simulations also reveal that a single surfactant chain needs to displace up to five ethanol molecules to adsorb onto the surface. The end result is more favorable ethanol adsorption which agrees with the experimental analysis of similar oil/iron oxide systems also reported in this work.Industr

From food to mobility: investigating a screening assay for new automotive antioxidants using the stable radical DPPH

By taking inspiration from the food industry, an assay was investigated as a potential screening tool to test the efficiency of new phenolic antioxidants. The method was based on the spectrophotometric measurement of the stable free radical 1,1-diphenyl-2-picryl hydrazyl (DPPH) which, in its radical form, has an absorbance maxima at 515 nm. The disappearance of this absorbance band, upon reaction with an antioxidant, was monitored to reveal the kinetic pathway of the reaction, which was defined simply as either fast, medium or slow. Adaptation of the assay was attempted for application to biofuels and oil-based automotive fluids whereby the effect of polar and non-polar solvents on the kinetics of the reaction was investigated. In addition, the stoichiometry of the radical scavenging reaction was also analysed to give an insight into the structure-activity relationships of phenolic antioxidants

Adsorption of 4-n-Nonylphenol, Carvacrol, and Ethanol onto Iron Oxide from Nonaqueous Hydrocarbon Solvents.

The adsorption of 4-n-nonylphenol (4NP), carvacrol, and ethanol onto the surface of iron oxide from nonaqueous solutions is presented. It is found that adsorption of 4NP from alkanes is strong and proceeds to monolayer formation, where the molecules are essentially "upright". However, at high relative concentrations, ethanol successfully out-competes 4NP for the iron oxide surface. Estimates of the enthalpy and entropy of binding of 4NP were found to be exothermic and entropically disfavored. Sum frequency generation vibrational spectroscopy data indicate some evidence of binding through a phenolate anion, despite the nonpolar, nonaqueous solvent. Carvacrol is also found to adsorb as a monolayer where the molecules are lying "flat". The adsorption of ethanol onto iron oxide from dodecane was investigated through the use of quantitative NMR, which is a convenient analytical technique for measuring adsorption isotherms. It was concluded that ethanol does not form adsorbed monolayers on the surface. Instead, it partitions onto the surface as a surface-enhanced local phase separation related to its poor solubility in alkane solvents.B

Facile Synthesis of Functionalised Hyperbranched Polymers for Application as Novel, Low Viscosity Lubricant Formulation Components

A novel, previously unreported, method for synthesising hyperbranched (HB) materials is detailed. Their use as additives to produce lubricant formulations that exhibit enhanced levels of wear protection and improved low-temperature oil viscosity and flow is also reported. The lubricant formulations containing HB additives were found to exhibit both significantly lower viscosities and improved in-use film-forming properties than the current industry standard formulations. To achieve this, alkyl methacrylate oligomers (predominantly dimers and trimers) were synthesised using catalytic chain transfer polymerisation. These were then used as functional chain transfer agents (CTA) to control the polymerisation of divinyl benzene (DVB) monomers to generate highly soluble, high polydispersity HB polymers. The level of dimer/trimer purification applied was varied to define its influence on both these HB resultant structures and the resultant HB additives’ performance as a lubricant additive. It was shown that, while the DVB acted as the backbone of the HB, the base oil solubility of the additive was imparted by the presence of the alkyl chains included in the structure via the use of the oligomeric CTAs

New records and noteworthy data of plants, algae and fungi in SE Europe and adjacent regions, 12

This paper presents new records and noteworthy data on the following taxa in SE Europe and adjacent regions: red algae Hildenbrandia rivularis, saprotrophic fungus Cryptomarasmius corbariensis, lichenised fungi Lecanora stenotropa, Micarea misella and Sticta sylvatica, liverworts Fossombronia caespitiformis and Peltolepis quadrata, mosses Dicranoweisia cirrata and Fissidens exilis, horsetail Equisetum × moorei, gymnosperm Juniperus virginiana, monocots Galanthus reginae-olgae subsp. vernalis and Spiranthes spiralis and dicots Linaria pelisseriana, Parthenocissus quinquefolia, Pilosella rhodopea and Taraxacum erythrospermum are given within SE Europe and adjacent regions

Increasing the antioxidant capability via the synergistic effect of coupling diphenylamine with sterically hindered phenol

A series of novel diphenylamine-phenol antioxidants were synthesised that combined the two antioxidant types into a single molecule. These antioxidants were then functionalised with alkyl chains to aid their solubility in hydrocarbon media. As part of a structure-activity study, diphenylamine derivatives were also generated bearing carboxylic acid functionalities in either the ortho, meta or para position with respect to the secondary amine. Methyl or ethyl spacers were also incorporated between the carboxylic acid and the aromatic ring. The antioxidant ability of the diphenylamine-phenols was evaluated using Differential Scanning Calorimetry (DSC) and compared to commercially available antioxidants Irganox L135 and Irganox L57 both as individual components and when blended together. The diphenylamine-phenol antioxidant with an ethyl spacer between the diphenylamine and carboxylic acid in the meta position with respect to the secondary amine functionality showed an impressive oxidation induction time of ca. 24 minutes in direct comparison with the blend of Irganox L135 and Irganox L57 (ca. 16 minutes)

Measurements of the charge asymmetry in top-quark pair production in the dilepton final state at s √ =8 TeV with the ATLAS detector

Measurements of the top-antitop quark pair production charge asymmetry in the dilepton channel, characterized by two high-pT leptons (electrons or muons), are presented using data corresponding to an integrated luminosity of 20.3  fb−1 from pp collisions at a center-of-mass energy s√=8  TeV collected with the ATLAS detector at the Large Hadron Collider at CERN. Inclusive and differential measurements as a function of the invariant mass, transverse momentum, and longitudinal boost of the tt¯ system are performed both in the full phase space and in a fiducial phase space closely matching the detector acceptance. Two observables are studied: AℓℓC based on the selected leptons and Att¯C based on the reconstructed tt¯ final state. The inclusive asymmetries are measured in the full phase space to be AℓℓC=0.008±0.006 and Att¯C=0.021±0.016, which are in agreement with the Standard Model predictions of AℓℓC=0.0064±0.0003 and Att¯C=0.0111±0.0004