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31.
Norman S. Allen Alfonso Chirinos-Padron John H. Appleyard Terence J. Henman 《Polymer Degradation and Stability》1983,5(2):105-112
The effect of calcium and nickel stearates on the photo-stabilising action and photo-decomposition of one calcium and two nickel metal chelates in polypropylene has been examined using infra-red and ultraviolet derivative spectroscopy. Whereas the presence of calcium stearate antagonises the photo-stabilising action of one nickel chelate, Irgastab 2002, it strongly synergises with the other, Cyasorb UV 1084. The presence of nickel stearate synergises with the calcium chelate, Irganox 1425, in unprocessed polymer whereas, in processed polymer, it exhibits antagonism. Rates of photo-decomposition of the metal chelates are also affected by metal stearates. The data suggests that, with these nickel chelates, there might be some degree of metal exchange with certain metal stearates. 相似文献
32.
Norman S. Allen Alfonso Chirinos-Padron John H. Appleyard 《Polymer Degradation and Stability》1982,4(3):223-237
The photo-stabilising action of three metal chelates—nickel (II) 2,2′ thiobis (4-tert-octylphenylato) n-butylamine and the nickel and calcium derivatives of bis (ethyl-3,5-di-tert-butyl-4-hydroxybenzyl) phosphonate, in polypropylene—is examined using normal and second order derivative ultraviolet, infra-red and phosphorescence spectroscopic techniques and hydroperoxide analysis. Whilst all three stabilisers quenched the phosphorescence emission of a powerful photo-sensitiser, benzophenone, there was no protective action during photo-sensitised oxidation of the polymer. In the case of anthraquinone, there was no quenching and no protection. Processing history plays a dominant rôle in controlling the photo-stabilising performance of the chelates. Each stabiliser operates differently, being dependent on its relative stability during processing and photo-oxidation and on the formation and destruction of polymeric and antioxidant hydroperoxides during processing. Metal chelates operate by inhibiting polymer hydroperoxide formation during processing and acting as ultraviolet stable chain terminators or by giving products during the early stages of photo-oxidation which are themselves effective stabilisers. 相似文献
33.
The C-methylation of the potassium salt of 1-t-butyl-2-phenyl-3-(p-phenylbenzoyl)azetidine ( 1a ) with methyl iodide was studied in three solvents, and the stereochemical outcome of the reaction was shown to be dependent upon the solvent used. These results are rationalized in terms of the probable relative rates of the reaction in the various solvents and/or the effect of solvent on the structure of the anionic intermediate. Similar treatment of the potassium salt of 1-t-butyl-2-phenyl-3-benzoylazetidine ( 3a ) in ethyl ether gave a comparable result. The configurations of the epimeric C-methyl products ( 2a and 2b , and 4a ) were assigned on the basis of their spectral properties. With the aid of spectral data for a model compound, l-t-butyl-3-benzoyl-azetidine ( 5 ), several stereostructure-spectra relationships for 3-azetidinyl ketones are presented. 相似文献
34.
Hettiarachchi K Green CE Ramanathan-Girish S Wu B Jackson CJ Ridge S Salem MA Lanser ME 《Journal of chromatography. A》2001,924(1-2):471-481
This paper describes a pharmacokinetic study performed in Sprague-Dawley rats after i.v. administration of a single 6-mg/kg dose of 2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-(3-iodo-E-allyl)nortropane (Altropane). Plasma samples were collected from the retro-orbital sinus at times up to 3 h after drug administration, extracted by solid-phase extraction, and the drug levels determined by capillary electrophoresis (CE). Pharmacokinetic parameters were determined by a standard noncompartmental model using WinNonlin version 1.5. The maximum plasma concentrations, clearances of the drug, and areas under the curve for male and female rats were 5.74 and 7.26 microg/ml, 135.7 and 98.5 ml/kg x min, and 44.23 and 60.92 microg x min/ml, respectively. The drug was cleared very rapidly from the systemic circulation, with a terminal t(1/2) of 7 to 10 min and a mean residence time of about 11 min for both sexes. The volume of distribution was approximately 1 l/kg. No metabolites were detected when the samples were analyzed individually. However, after samples were pooled and concentrated, traces of two unknown peaks that may represent metabolites were detected in concentrates from the last two timepoints. Part I of this work [J. Chromatogr. A, 895 (2000) 87] describes validation of CE methods for the analysis of aqueous and plasma samples of Altropane, including its solid-phase extraction from rat plasma. 相似文献
35.
Abstract —Semi-empirical formulas for the ultraviolet erythema dose derived in an earlier paper are used to deduce an ultraviolet photoclimatology. We calculate the climatology of daily erythema radiation doses for the northern hemisphere at 5d? latitude intervals. Similar dose calculations are also performed specifically for ten metropolitan areas. Effects of seasonal and geographic variations of ozone, turbidity, and cloudiness on the local erythema doses are also investigated. We present a simple approximate analytic formula for the annual erythema dose as a function of latitude, cloud cover, and ground albedo for use in connection with studies of the epidemiology of skin cancer. The implications of possible ozone depletion due to a future fleet of supersonic aircraft in the stratosphere are discussed. These calculations are made for a normal ozone thickness of 0.32 cm and for a 5, 10, 20, and 50 per cent ozone reduction. 相似文献
36.
Norman S. Allen Alfonso Chirinos-Padron John H. Appleyard 《Polymer Degradation and Stability》1984,6(3):149-176
The interactions of three metal chelates (nickel (II) 2,2′-thiobis (4-tertoctyl-phenolato), n-butylamine (Cyasorb UV 1084) and the nickel and calcium derivatives of bis(ethyl-3,5-di-tert-butyl-4-hydroxybenzyl) phosphonate (Irgastab 2002 and Irganox 1425)) with other commercial additives, in the stabilisation of polypropylene film, are examined using normal and second-order derivative ultraviolet and infra-red spectroscopic techniques. It is shown that the observed behaviour is dependent on the particular additive, the processing history of the polymer and the metal chelate concerned, and is therefore highly complex. All three chelates show antagonism with a hindered piperidine, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin 770), in unprocessed polymer, whereas one of the chelates behaves synergistically with this additive in processed samples. The chelates also show antagonism with a primary antioxidant, tris((3-(3′,5′-di-tert-butyl-4-hydroxybenzyl)-2′'-aceto-ethyl)) isocyanurate (Goodrite 3125), whereas, with a secondary antioxidant, distearyl pent-aerithrityl diphosphite (Weston 618), their behaviour is synergistic in both unprocessed and processed polymer. Two of the chelates show synergism with 2-hydroxy-4-n-octoxybenzophenone (Cyasorb UV 531), the remaining chelate showing antagonism. Mixtures containing a three-additive system show a more complex behaviour. The results are explained in terms of hydroperoxide decomposition, inhibition, stabiliser dispersion, ultraviolet stability and additive compatibility. 相似文献
37.
Tay-Yean Lin Charles A. Kingsbury Jules Adelfang Norman H. Cromwell 《Journal of heterocyclic chemistry》1985,22(4):1017-1020
The synthesis and spectral characteristics of certain bis(1-alkyl-3-phenyl-2-aziridinyl)ketones are reported. The reactions of 1,2,4,5-tetrabromo-1,5-diphenyl-3-pentanone ( 2 ) with primary amines are assumed to have a mechanism similar to that of a simple dibromo-ketone. The so-called cis, cis- or trans, trans-configurations of the bis-aziridinylketones were determined by 1H and 13C nmr spectra. 相似文献
38.
Synthesis of 9-methyl-1H-[1,4]thiazino[3,2-g]quinoline-2,5,10(3H)-trione (4), from N-(4-bromo-2,5-dimethoxyphenyl)acetamide (23) is described. Oxidative cyclisation of 2,2'-disulfanediylbis[N-(2,5-dimethoxyphenyl)acetamide] (19) to 5,8-dimethoxy-2H-1,4-benzothiazin-3(4H)-one (7b) is also reported. 相似文献
39.
Okamura WH Zhu GD Hill DK Thomas RJ Ringe K Borchardt DB Norman AW Mueller LJ 《The Journal of organic chemistry》2002,67(5):1637-1650
Isotope-labeled drug molecules may be useful for probing by NMR spectroscopy the conformation of ligand associated with biological hosts such as membranes and proteins. Triple-labeled [7,9,19-(13)C(3)]-vitamin D(3) (56), its 25-hydroxylated and 1 alpha,25-dihydroxylated metabolites (58 and 68, respectively), and other labeled materials have been synthesized via coupling of [9-(13)C]-Grundmann's ketone 39 or its protected 25-hydroxy derivative 43 with labeled A ring enyne fragments 25 or 26. The labeled CD-ring fragment 39 was prepared by a sequence involving Grignard addition of [(13)C]-methylmagnesium iodide to Grundmann's enone 28, oxidative cleavage, functional group modifications leading to seco-iodide 38, and finally a kinetic enolate S(N)2 cycloalkylation. The C-7,19 double labeling of the A-ring enyne was achieved by the Corey-Fuchs/Wittig processes on keto aldehyde 11. By employing these labeled fragments in the Wilson-Mazur route, the C-7,9,19 triple-(13)C-labeled metabolites 56, 58, and 68 as well as other (13)C-labeled metabolites have been prepared. In an initial NMR investigation of one of the labeled metabolites prepared in this study, namely [7,9,19-(13)C(3)]-25-hydroxyvitamin D(3) (58), the three (13)C-labeled carbons of the otherwise water insoluble steroid could be clearly detected by (13)C NMR analysis at 0.1 mM in a mixture of CD(3)OD/D(2)O (60/40) or in aqueous dimethylcyclodextrin solution and at 2 mM in 20 mM sodium dodecyl sulfate (SDS) aqueous micellar solution. In the SDS micellar solution, a double half-filter NOESY experiment revealed that the distance between the H(19Z) and H(7) protons is significantly shorter than that of the corresponding distance calculated from the solid state (X-ray) structure of the free ligand. The NMR data in micelles reveals that 58 exists essentially completely in the alpha-conformer with the 3 beta-hydroxyl equatorially oriented, just as in the solid state. The shortened distance (H(19Z))-H(7)) in micellar solutions as compared to that in the solid state is most easily rationalized on the basis that the 5(10)-torsion angle in 58 is decreased in micellar solutions as compared to that in the solid state. 相似文献
40.
[reaction: see text] Psymberin is a sponge-derived natural product that shows striking selectivity as a cytotoxic agent. Conformational mobility has precluded stereochemical assignment for the acyl fragment of this molecule (psymberic acid) by NMR. Herein we report stereoselective syntheses of all four stereoisomers of psymberic acid. A comparison of the acid-mediated cyclization products of these compounds to the product of psymberin's acidic methanolysis showed the stereochemical configuration of this fragment to be 4S,5S. 相似文献