Modification of poly(vinyl chloride). XXXI. Crosslinking of poly(vinyl chloride) with 2-R-4,6-dithiol-s-triazine and metal activators

Crosslinking of poly(vinyl chloride) (PVC) with 2-R-4,6-dithiol-s-triazine (R-DT) and metal activators has been studied to determine crosslinking rate constants, induction periods, and apparent activation energy and the final efficiency of crosslinking agents. The rate constants were about 1.4–7.5 min^?1 and the induction periods were about 6.8–24.3 min for various kinds of R-DT at 180°C. The activation energy was about 16.6–33 kcal/mol over the temperature range 160–195°C. The rate constants were strongly influenced by 2-substituted groups (R) in R-DT and increased in the order R′O-? R′NH-< (R′)₂N, where R′ is an alkyl or aryl group. Further, the rate constants increased in the order of: metal carboxylates < metal carboxylates < metal oxides for the activators and in the order of: Pb < Mg < Ca < Ba < Na for metal atoms. The final efficiency was about 75–80% for the activators such as MgO, MgCO₃, PbO, and SnO. The activators containing Na, Ca, and Ba atoms, however, gave final efficiency of more than 100%.     

Thermal decomposition mechanisms of tert-alkyl peroxypivalates studied by the nitroxide radical trapping technique

The thermolysis of a series of tert-alkyl peroxypivalates 1 in cumene has been investigated by using the nitroxide radical-trapping technique. tert-Alkoxyl radicals generated from the thermolysis underwent the unimolecular reactions, beta-scission, and 1,5-H shift, competing with hydrogen abstraction from cumene. The absolute rate constants for beta-scission of tert-alkoxyl radicals, which vary over 4 orders of magnitude, indicate the vastly different behavior of alkoxyl radicals. However, the radical generation efficiencies of 1 varied only slightly, from 53 (R = Me) to 63% (R = Bu(t)()), supporting a mechanism involving concerted two-bond scission within the solvent cage to generate the tert-butyl radical, CO(2), and an alkoxyl radical. The thermolysis rate constants of tert-alkyl peroxypivalates 1 were influenced by both inductive and steric effects [Taft-Ingold equation, log(rel k(d)) = (0.97 +/- 0. 14)Sigmasigma - (0.31 +/- 0.04)SigmaE(s)(c), was obtained].     

Photocyclisierungen von 1, 1'-Polymethylen-di-2-pyridonen. 46. Mitteilung über Photoreaktionen

Photocyclization of 1, 1′-Polymethylene-di-2-pyridones . Benzophenone sensitized irradiation of the four dipyridones 1-4 gave the internal photocyclization products 6 (64%, Scheme 4), 7 (60%, Scheme 5), 8 (Scheme 6), and 11 (26%, Scheme 7), respectively. The decamethylene compound 5 yielded only polymeric material. The primary [2+2] photoproduct 8 from dipyridone 3 (Scheme 6) is relatively unstable. Further irradiation or heating to 65° induced a Cope rearrangement to give compound 9 which, on heating to 137°, was converted into the isomeric compound 10 . This product, as well as the other photoproducts mentioned, are rearranged back to their respective starting materials upon direct irradiation with 254 nm light or by heating to higher temperatures. The various possibilities for cycloadditions of pyridones are discussed as well as the possible factors which are responsible for the highly regioselective photoreactions of the dipyridones 1–4 .     

Controlling the incorporation and release of C60 in nanometer-scale hollow spaces inside single-wall carbon nanohorns

We succeeded in large-scale preparation of single-wall carbon nanohorns (SWNH) encapsulating C60 molecules in a liquid phase at room temperature using a "nano-precipitation" method, that is, complete evaporation of the toluene from a C60-SWNH-toluene mixture. The C60 molecules were found to occupy 6-36% of the hollow space inside the SWNH, depending on the initial quantity of C60. We showed that the C60 in C60@SWNHox was quickly released in toluene, and the release rate decreased by adding ethanol to toluene. Numerical analysis of the release profiles indicated that there were fast and slow release processes. We consider that the incorporation quantity and the release rate of C60 were controllable in/from SWNHs because SWNHs have large diameters, 2-5 nm.     

Simultaneous determination of residual antiparasitic lactones in bovine muscle and liver by liquid chromatography with fluorescence detection

Abamectin, doramectin, eprinomectin, ivermectin, milbemectin, and moxidectin in bovine muscle and liver were extracted with acetonitrile. The extracts were partitioned with n-hexane and then evaporated to dryness. The residue was cleaned up on Bond Elute NH2 cartridge, and the drugs were eluted from the cartridge with methanol-ethyl acetate (3 + 7). The eluate was evaporated to dryness, and residues were derivatized with N,N-dimethylformamide-acetic anhyride-1-methylimidazole. The derivatives were determined by liquid chromatography with fluorescence detection. Recoveries of the 6 drugs were 79.6-63.8% in muscle and 71.6-60.6% in liver at 0.01 ppm levels. The quantitation limits were 5 ppb for each drug.     

Zooxanthellamide A, a novel polyhydroxy metabolite from a marine dinoflagellate of Symbiodinium sp.

A novel polyhydroxy metabolite named Zooxanthellamide A, C₁₂₈H₂₂₂N₂O₅₄S₂, was isolated from a cultured marine dinoflagellate, Symbiodinium sp., and the chemical structure was determined by spectroscopic methods.     

Saccharification and alcohol fermentation in starch solution of steam-exploded potato

Steam explosion pretreatment of potato for the efficient production of alcohol was experimentally studied. The amount of water-soluble starch increased with the increase of steam pressure, but the amounts of methanol-soluble material and Klason lignin remained insignificant, regardless of steam pressure. The potatoes exploded at high pressure were hydrolyzed into a low molecular liquid starch, and then easily converted into ethanol by simultaneous saccharification and fermentation using mixed microorganisms: an amylolytic microorganism,Aspergillus awamori, and a fermentation microorganism,Saccharomyces cerevisiae. The maximal ethanol concentration was 4.2 g/L in a batch culture at 15 g/L starch concentration, and 3.6 g/L in a continuous culture fed the same starch concentration. In the fed-batch culture, the maximal ethanol concentration increased more than twofold, compared to the batch culture.     

Carbon-13 NMR spectroscopy of acrylic monomer and Lewis acid complexes

¹³C NMR spectra of acrylic monomers complexed with a Lewis acid were measured and their electronic structures discussed in relation to their alternating copolymerizability. The β-carbon of acrylonitrile and methacrylonitrile showed a downfield shift due to the complex formation with the Lewis acid, while the α-carbon showed an upfield shift and the nitrile carbon showed no significant shift. The degree of shift of olefinic carbons decreased in the following order: AlCl₃ > EtAlCl₂ > Et_1.5AlCl_1.5 > Et₂AlCl > SnCl₄, EtOAlCl₂ > Et(EtO)AlCl, which seems to run parallel to the Lewis acidity and acid strength. On the other hand, the chemical shift of olefinic carbons of methyl acrylate, methyl methacrylate, and olefinic diesters was influenced little by complex formation with Lewis acids, whereas the carbonyl and alkoxyl carbons were deshielded significantly by the complex formation. These results are discussed in terms of electron distribution on the carbons and an alternating polymerization mechanism.     

A problem in the spectrophotometric determination of dissolved total phosphorus in brackish anoxic waters

When dissolved total phosphorus in anoxic brackish waters was determined spectrophotometrically by the heteropoly molybdenum blue method after oxidation with potassium peroxodisulfate, negative dissolved organic phosphorus contents were obtained from the differences between the total phosphorus and inorganic phosphorus contents. A major cause of this inconsistency is coprecipitation of phosphate with the colloidal hydrated iron(III) oxide produced fro miron in these waters, or the formation of iron(III) phosphate during the oxidation process. The problem can be avoided by oxidation with nitric and perchloric acids.