Oxidative stability derivatives

FIGURE 6.45 Inability of 5a-substituted derivatives to form structures analogous to o-QM 3 causes increased oxidative stability as in compounds 71 and 72. 5-(p-Hydroxyphenyl)-y-tocopherol (73) is oxidized to the conjugatively stabilized o-QM 74, the phenylogous a-tocored (75). 

As part of a multi-technique investigation (see also discussion under mid-infrared spectroscopy later), Corrales et al. [13] plotted the carbonyl index for films prepared from three grades of polyethylenes a high-density PE (HDPE), a linear low-density PE (LLDPE) and a metallocene PE (mPE) (see Figure 5). In this study, the data trend shown in Figure 5 correlated well with activation energies derived from the thermal analysis, which showed that the thermal-oxidative stability followed the order LLDPE > mPE > HDPE, whereas the trend... 

J.-I. Lee, G. Klaemer, and R.D. Miller, Oxidative stability and its effect on the photoluminescence of poly(fluorene) derivatives end group effects, Chem. Mater., 11 1083-1088, 1999. 

Little is known about valence-shell expansion reactions among still higher row elements, but the considerable oxidative stability of silicones and of tetraalkyl derivatives of group IV elements suggests that valence shell-expansion doesn t provide an easy path for oxygen attack in this group. 

The stability of the products from coal-derived syncrudes must be examined carefully. Many unique compounds are present in these syncrudes peri-condensed aromatics and naphthenes, oxygen compounds, and asphaltene-like hydrocabons. Traces of these compounds may remain in the hydrotreated product and their effect on jet, thermal, and oxidation stabilities cannot be predicted from the behavior of petroleum products. 

For jet fuels, a visual rating of No. 1 or No. 2 is required at 260°C in the jet fuel thermal oxidation stability test (JFTOT-ASTM D 3241). Also, a pressure drop of less than 25 mm Hg is required in this test, As shown in Table XI, the 250°F+ product from hydrotreated Illinois H-Coal syncrude passes both parts of the JFTOT test, even when the jet fuel is not refined enough to pass three other specifications aromatic content, smoke point, and gum content. When jet fuels are prepared from coal-derived syncrudes, the smoke point appears to be the limiting specification. The gum content and end point specifications are met when the jet fuels are distilled at 600°F. 

Similarly to bis(octylphenoxy)dithiophosphate, one can obtain other bis(alkylphenoxy)derivatives of dithiophosphoric acid. As mentioned above, these ethers are veiy efficient additives for lubricant oils used in intensive operation engines. An addition of 1-5% of these substances greatly increases thermal oxidative stability and anticorrosion properties of lubricant oils and reduce varnish formation in engines. 

Muramatsu H, Hayashi T, Kim YA, Shimamoto D, Kim YJ, Tantrakarn K, Endo M, Terrenes M, Dresselhaus MS. Pore structure and oxidation stability of double-walled carbon nanotube-derived bucky paper. Chem Phys Lett 2005 414 444-448. 

The Biodiesel Stability (BIOSTAB) project, supported by the European Commission, was initiated in 2001 to establish clear criteria and analytical methods for the monitoring biodiesel fuel stability (Various, 2003 Prankl, 2002). The resulting unified method, EN 14112 (Anon., 2003c) established a means for measuring oxidative stability utilizing the Rancimat or oxidation stability instruments. This test method was essentially developed from standards employed in the fats and oils industry to measure isothermally the induction period for oxidation of fatty derivatives. At present, both biodiesel fuel standards ASTM D 6751 (Anon., 2007a) and EN 14214 (Anon., 2003b) include an oxidative stability specification based on measurement by method EN 14112. 

Anon. 2003c. In EN14112 Fat and Oil Derivatives - Fatty Acid Methyl Esters (FAME)— Determination of Oxidation Stability (Accelerated Oxidation Test. Brussels European Committee for Standardization. 

Loh, S. K., Chew, S. M., and Choo, Y. M. 2006. Oxidative Stability and Storage Behavior of Fatty Acid Methyl Esters Derived from Used Palm Oil. I. Am. Oil Chem. Soc., 83, 947-952. 

Most decaphenylmetailocenes also exhibit an unsurpassed thermal stability for sandwich complexes. The decaphenyl Ge, Sn, and Pb derivatives do not decompose until above 350°C (under nitrogen) (39), in contrast with around 100°C for the decabenzyl analogs (106). For sym-penta- and decaphenylferrocene and -ruthenocene an extraordinary degree of thermal and oxidative stability is noted (40) they are unchanged in air ( ) at 315°C and volatilize only at 250-300° C in the mass spectrometer. 

Ruthenium(II) complexes may also be used to oxidize N-Boc hydroxylamine in the presence of tert-butylhydroperoxide (TBHP) to the corresponding nitroso dieno-phile, which is subsequently trapped by cyclohexa-1,3-diene to give the hetero Diels-Alder adduct (Entry 1, Scheme 10.26) [51]. A triphenylphosphine oxide-stabilized ruthenium(IV) oxo-complex was found to be the catalytically active species. Use of a chiral bidentate bis-phosphine-derived ruthenium ligand (BINAP or PROPHOS) result in very low asymmetric induction (8 and 11%) (Entry 2, Scheme 10.26). The low level of asymmetric induction is explained by the reaction conditions (in-situ oxidation) that failed to produce discrete, stable diastereomerically pure mthenium complexes. It is shown that ruthenium(II) salen complexes also catalyze the oxidation of N-Boc-hydroxylamine in the presence of TBHP, to give the N-Boc-nitroso compound which can be efficiently trapped with a range of dienes from cyclohepta-1,3-diene (1 h, r.t., CH2CI2, 71%) to 9,10-dimethylanthracene (96 h, r.t., CH2CI2,... 

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