A study of the radiation degradation of styrene/alkane and α-methylstyrene/alkane copolymers

The effects of copolymer composition and microstructure on the radiation chemistry of styrene/alkane and alpha-methylstyrene/alkane copolymers have been studied. The primary radical species formed on radiolysis of the copolymers at 77 K, and identified by ESR spectroscopy, are the same as those formed during radiolysis of the homopolymers. The yields of radicals for the copolymer are as predicted assuming that the cross-section is proportional to the electron density of each component; however, there is some evidence of radical migration to aromatic groups at 77 K. Changes in molecular structure on irradiation were detected by using C-13 NMR spectroscopy. Evidence of the consumption of terminal double bonds, and chain scission in alpha-methylstyrene/alkane copolymers was found. Measurements of viscosity supported the mechanism of cross-linking predominating in styrene/alkane copolymers, while in alpha-methylstyrene/alkane copolymers chain scission was the major result of irradiation. (C) 2003 Society of Chemical Industry.

Scorpionate complexes as catalysts for alkane functionalization

A survey of the scorpionate tris(pyrazolyl)methane complexes synthesized by our group is presented, as well as their structural features and catalytic applications toward the funtionalization of linear and cyclic light alkanes.

A Hexanuclear Mixed-Valence Oxovanadium(IV,V) Complex as a Highly Efficient Alkane Oxidation Catalyst

The new hexanuclear mixed-valence vanadium complex [V3O3(OEt)(ashz)(2)(mu-OEt)](2) (1) with an N,O-donor ligand is reported. It acts as a highly efficient catalyst toward alkane oxidations by aqueous H2O2. Remarkably, high turnover numbers up to 25000 with product yields of up to 27% (based on alkane) stand for one of the most active systems for such reactions.

Electrochemical porperties of (H5-C5Me5)-rhodium and – iridium complexes Bis(pyrazolyl)alkane ligands

The electrochemical properties of rhodium(III) 1-3 and iridium(III) 4-6 complexes containing bis(pyrazolyl)alkane ligands [MCp*Cl(R2C(3,5-R'2pz)2)]X (M = Rh (1) or Ir (4), R = R' = H, X = Cl; M = Rh (2) or Ir (5), R=H,R'=Me,X=Cl;M=Rh(3) or Ir (6), R=Me,R'=H,X=OTf;pz=pyrazolyl;Cp*=η5-C5Me5) were investigated by cyclic voltammetry and controlled potential electrolysis. They exhibit two sequential irreversible reductions assigned to the MIII → MII and MII → MI reductions, which are dependent on the methylation of the bis(pyrazolyl)alkane ligands.

Application of the N-alkane molecular alloys to thermally protected containers for catering

A thermally controlled transport device was designed and tested. As hot food needs to be transported at temperatures between 60 and 70ºC in order to avoid contamination by microorganisms, the use of Molecular Alloy Phase Change Materials (MAPCM) can lead to improvements in this field of application. A heat transfer numerical simulation of the box used for transporting the food was conducted. Despite obvious simplifications, a good agreement between numerical simulation and experimental results was obtained. Furthermore, we compared our experimental results with those from other experiments related to the transport of hot food. Here, pizza is taken as the example, and it is shown that delivering time can be increased three-fold.

Correlation and prediction of mixing thermodynamic properties of ester-containing systems Ester+alkane and ester+ester binary systems and the ternary dodecane+ethyl pentonoate+ethyl ethanoate

[EN]Excess thermodynamic properties VE m and HE m, have been measured for the ternary mixture dodecane + ethyl pentanoate + ethyl ethanoate and for the corresponding binaries dodecane + ethyl pentanoate, dodecane + ethyl ethanoate, ethyl pentanoate + ethyl ethanoate at 298.15 K. All mixtures show endothermic and expansive effects. Experimental results are correlated with a suitable equation whose final form for the excess ternary quantity ME contains the particular contributions of the three binaries (i–j) and a last term corresponding to the ternary, all of them obtained considering fourth-order interactions.

Measurements and correlations of the isobaric vapor-liquid equilibria of binary mixtures and excess properties for mixtures containing and alkyl (Methyl, Ethyl) butanoate with an alkane (Heptane, Nonane) at 101.32 kPa.

[EN]In this work, the measurements of the isobaric vapor−liquid equilibrium (VLE) data at 101.32 kPa and the excess molar volumes (vE), obtained at 10 K intervals of temperature in the range (288.15 to 328.15) K, for four binary systems comprised of methyl or ethyl butanoate with two alkanes (heptane and nonane) are presented.

Improvements in the experimentation and the representation of thermodynamic properties (iso-p VLE and y) of alkyl propanoate+alkane binaries

[EN]This paper presents the experimental measurements of isobaric vapor−liquid equilibria (iso-p VLE) and excess volumes (vE) at several temperatures in the interval (288.15 to 328.15) K for six binary systems composed of two alkyl (methyl, ethyl) propanoates and three odd carbon alkanes (C5 to C9). The mixing processes were expansive, vE > 0, with (δvE/δT)p > 0, and endothermic. The installation used to measure the iso-p VLE was improved by controlling three of the variables involved in the experimentation with a PC.

n-Alkane analyses from an transect of marine surface sediments off southwest Africa

An isobathic transect of marine surface sediments from 1°N to 28°S off southwest Africa was used to further evaluate the potential of the chain length distribution and carbon stable isotope composition of higher plant n-alkanes as proxies for continental vegetation and climate conditions. We found a strong increase in the n-C29-33 weighted mean average d13C values from -33 per mil near the equator to around -26 per mil further south. Additionally, C25-35n-alkanes reveal a southward trend of increasing average chain length from 30.0 to 30.5. The data reflect the changing contribution of plants employing different photosynthetic pathways (C3 and C4) and/or being differently influenced by the environmental conditions of their habitat. The C4 plant proportions calculated from the data (ca. 20% for rivers draining the rainforest, to ca. 70% at higher latitude) correspond to the C4 plant abundance in continental catchment areas postulated by considering prevailing wind systems and river outflows. Furthermore, the C4 plant contribution to the sediments correlates with the mean annual precipitation and aridity at selected continental locations in the postulated catchment areas, suggesting that the C4 plant fraction in marine sediments can be used to assess these environmental parameters.

Age determination and n-Alkane concentration of Arctic Ocean sediment cores

We have reconstructed the surface water environment of the Arctic Ocean over the last ? 50,000 years using measurements of the organic nitrogen and carbon isotope ratios, carbonate and total organic carbon concentrations (TOC), and terrestrial biomarkers (lignin and long-chain n-alkanes) in four multicores. Variations in nitrogen isotope ratios that are concordant with TOC and carbonate concentrations (representing foraminifera and excluding ice-rafted-debris) reflect differences in relative nutrient utilization of phytoplankton in the surface waters. However, d15N variations also appear to be dependent on the stratification of the water column and therefore potentially track the exchange of nutrients between deep and surface waters. Low Last Glacial Maximum (LGM) d15N values and higher Holocene values are opposite to those recorded in the Southern Ocean. The Arctic Ocean with higher nutrient utilization today compared to the LGM therefore acts as a counterpart to the Southern Ocean, although the global impact on carbon dioxide variations compared to the Southern Ocean is probably low.