Search results for "Alkane"

Cytotoxic Activity and Composition of Petroleum Ether Extract from Magydaris tomentosa (Desf.) W. D. J. Koch (Apiaceae)

2015

The petroleum ether extract of Magydaris tomentosa flowers (Desf.) W. D. J. Koch has been analyzed by GC-MS. It is mainly constituted by furanocoumarins such as xanthotoxin, xanthotoxol, isopimpinellin, and bergaptene. Other coumarins such as 7-methoxy-8-(2-formyl-2-methylpropyl) coumarin and osthole also occurred. The antiproliferative activity of Magydaris tomentosa flower extract has been evaluated in vitro on murine monocye/macrophages (J774A.1), human melanoma (A375) and human breast cancer (MCF-7) tumor cell lines, showing a major activity against the latter.

Isobaric Vapor−Liquid Equilibrium in the Systems 2,3-Dimethylpentane + Methyl 1,1-Dimethylethyl Ether, + Diisopropyl Ether and + Methyl 1,1-Dimethylp…

1999

New, consistent vapor−liquid equilibrium data for the binary systems 2,3-dimethylpentane + methyl 1,1-dimethylethyl ether, + diisopropyl ether, and + methyl 1,1-dimethylpropyl ether are reported at 101.3 kPa. The measured systems deviate slightly from ideal behavior, and only the system methyl 1,1-dimethylpropyl ether + 2,3-dimethylpentane presents an azeotrope. The activity coefficients for the solutions were correlated with their compositions by the Wilson, UNIQUAC, and NRTL models. Wisniak−Tamir equations were used to correlate the boiling points of the solutions with their compositions.

Adsorption and diffusion of linear and dibranched C6 paraffins in a ZSM-5 zeolite

2002

The adsorption of n-hexane and 2,2-dimethylbutane on a commercial ZSM-5 zeolite is studied under isothermal and isobaric conditions. ZSM-5 exhibits two different behaviours with linear and dibranched alkanes. A substep at 4 molec.uc−1 is observed on the adsorption isotherm of n-hexane at 348 K. A singular adsorption-desorption process is evidenced on the adsorption isobar at 5.5 kPa with 2,2-dimethylbutane at a temperature close to 343 K when the sample is activated at 298 K under vacuum. The diffusivities have been determined by fitting directly the uptake curves with a numerical resolution of second Fick's law based on finite difference method. Microporous diffusion seems to be rate limit…

Insights into the decomposition pathway of a lutetium alkylamido complex via intramolecular C–H bond activation

2017

Abstract Synthesis, characterization and reaction chemistry of lutetium alkylamido LLu(CH2SiMe3)(NHCPh3) (2), L = 2,5-[Ph2P=N(4-iPrC6H4)]2N(C4H2)–, is reported. Complex 2 undergoes cyclometalation of the NHCPh3 ligand at elevated temperatures to produce the orthometalated complex LLu(κ2−N,C-(NHCPh2(C6H4))) (3) which converts to 0.5 equivalents of bis(amido) LLu(NHCPh3)2 (4) upon heating at 80 °C for 24 h. Reaction of complex 2 with 4-dimethylaminopyridine (DMAP) does not promote alkane elimination nor imido formation. A kinetic analysis of the thermal decomposition of complex 2, supported by deuterium labelling studies and computational analysis (PBE0/def2-TZVP/SDD(Lu)), indicate direct Csp…

Measuring the Relative Reactivity of the Carbon-Hydrogen Bonds of Alkanes as Nucleophiles

2018

We report quantitative measurements of the relative reactivities of a series of C-H bonds of gaseous or liquid CnH2n+2 alkanes (n = 1-8, 29 different C-H bonds) towards insitu generated electrophiles (copper, silver, and rhodium carbenes), with methane as the reference. This strategy surpasses the drawback of previous model reactions of alkanes with strong electrophiles suffering from C-C cleavage processes, which precluded direct comparison of the relative reactivities of alkane C-H bonds.

Mo–V–Nb mixed oxides as catalysts in the selective oxidation of ethane

2003

Abstract Mo–V–Nb–O mixed metal oxides, obtained by heat-treatment in N 2 at 425 °C, have been studied as catalysts in the oxidative dehydrogenation of ethane. They present higher catalytic activity, while maintaining the same selectivity to ethylene, than the corresponding metal oxides calcined under air. Both amorphous and crystalline phases are present on active and selective catalysts. The implications of the presence of these phases as well as their physicochemical characteristics on the nature of active and selective sites are discussed.

2001

A new manganese(III) oxamato dimer possesing an unprecedented Mn2(μ-O2CR)(μ-OH2⋯O2 CR) core has been synthesised, structurally and magnetically characterised, and used as a catalyst for the oxidation of alkanes to alcohols and ketones by ButO2H and O2 in CH2Cl2 at rt.

Isomerization of C5–C7 n-alkanes on unidirectional large pore zeolites: activity, selectivity and adsorption features

2001

Abstract The hydroisomerization–hydrocracking of nC5–nC7 is studied with a 12MR unidirectional zeolite (ITQ-4). Selectivity and kinetic parameters indicate that differences in pore topology are more important than acidity for determining isomerization selectivity. The adsorption of the paraffins is determined by van der Waals interactions.

Liquid gas techniques for GC trace analysis

1990

Liquid gases (LG), i.e. low boiling compounds with vapor pressures below 5 bar at room temperature, are introduced as solvents for trace analyses. A system for preparin, diluting and handling LG solutions safely and conveniently in 5 to 500 μl amounts was developed as well as a syringe for direct injection of μl-LG samples into capillary GC. Even technical grade LG are of high purity. GC/FID of LG solutions (starting at −60°C) allows the separation of volatile traces from the solvent peak: e.g., dichloromethane can be measured in the picogram range.

Monolayers of dipalmitoylphosphatidylcholine at the oil-water interface

1995

Abstract Monolayers of dipalmitoylphosphatidylcholine at the interfaces waterbicylohexyl, waterdodecane and waterhexadecane were studied by fluorescence microscopy and thermodynamic measurements. The experiments show that the oil also partitions in the liquid condensed (LC) monolayer phase with concentration depending on the type of oil and the lateral pressure. In contrast to monolayers of dipalmitoylphosphatidylethanolamine the larger molecular area per head group enables oil partitioning in the LC phase even if there is a mismatch between the aliphatic tails of liquid and alkane.