Steric repulsion of polyoxyethylene groups for emulsion stability

Rapid coalescence was studied on liquid paraffin emulsion stabilized with a series of poly(oxyethylene) dodecyl ethers [C₁₂H₂₅ (EO),n=1, 2, 3, 4, 5, 6, 7, 8] and of poly(oxyethylene) nonylphenyl ethers [C₉H₁₉(EO) _n ,n=2, 4, 5, 6, 12]. The turbidity of emulsion was measured as a function of the solution pHs at constant ionic strength of 0.1 mol dm^–3.As a result, it was found that the emulsions (which were formed with C₁₂H₂₅(EO) _n surfactants having less than four oxyethylene groups, or with C₉H₁₉ (EO) _n surfactants having less than six oxyethylene groups) brought about rapid coalescence in the bulk pH between 2.03.5, which corresponded to the zero point of charges for the emulsions of the present systems. According to the Tadros treatment for emulsion flocculation, the total flocculation potennual was estimated as a function of the distance relative to the number of oxyethelene groups in the surfactants. The critical coalescence energy was obtained as –343 ×10^–19 J for the C₁₂H₂₅(EO) _n surfactants and –2.14×10^–19) J for the C₉H₁₉ (EO) _n surfactants. Furthermore, the formation of a hole for coalescence was estimated under the simple assumption that the coalescence was caused only by the energy dissipation.     

Synthesis of allenes via palladium-catalyzed hydrogen-transfer reactions: propargylic amines as an allenyl anion equivalent

Synthesis of allenes has been achieved by using palladium-catalyzed hydrogen-transfer reactions. Various propargylic amines, which were readily prepapred from iodobenzenes and propargylic amines by Sonogashira coupling reaction, underwent the hydrogen-transfer reaction in the presence of Pd2dba3.CHCl3/(C6F5)3P catalyst at 100 degrees C in dioxane for 24 h, giving the corresponding allenes in 43-99% yields. Various propargylic alcohols containing a propargylic aminomethyl group, synthesized by the addition of lithium acetylides of N,N-diisopropylprop-2-ynylamine to aldehydes and a ketone, also underwent the hydrogen-transfer reaction in the presence of Pd2dba3.CHCl3 catalyst and (C6F5)3P at 80 degrees C in dioxane, giving the corresponding allenes in 56-92% yields. In the current transformation, propargylic amines can be handled as an allenyl anion equivalent and introduced into various electrophiles to be transformed into allenes under palladium-catalyzed conditions.     

Synthesis to determine the absolute configuration of (−)-pyricuol, a phytotoxin isolated from rice blast disease fungus Magnaporthe grisea

The absolute configuration of (−)-pyricuol, a phytotoxin isolated from rice blast disease fungus Magnaporthe grisea, was determined to be R by synthetic studies.     

Synthesis,structure, and aromaticity of a hoop-shaped cyclic benzenoid [10]cyclophenacene

The first hoop-shaped cyclic benzenoid compounds, [10]cyclophenacene derivatives that contain 40 pi electrons, have been synthesized in three or four steps from [60]fullerene by rationally designed chemical modification. The compounds thus synthesized are chemically stable, yellow-colored, luminescent, and EPR-silent. X-ray crystallographic analysis provided high precision structural data sets. On the basis of these results and theoretical investigations, the new cyclic benzenoid molecules were proven to be aromatic.     

Lipase-catalyzed kinetic resolution of 3-butyn-2-ol

Optically active 3-butyn-2-ol, an important building block, was synthesized successfully using lipase-catalyzed kinetic resolution. Starting from the thus obtained 3-butyn-2-ol, several 4-aryl-substituted compounds were synthesized enantioselectively.     

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 .     

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.     

Reverse osmosis and fine structure of decrystallized acrylic acid grafted nylon 6 membranes

Nylon 6 film and acrylic acid grafted nylon 6 (GN) membrances were reacted with paraformaldehyde and lactic acid in the presence of acid catalysts. Decrystallized nylon 6 (DN) and decrystallized grafted nylon 6 (DGN) membranes were thus obtained. The cross sections of GN and DGN membranes were observed by a transmission electron microscope. Branch poly(acrylic acid) penetrated toward the center of the membrane and deposited homogeneously within the membrane as the extent of grafting exceeded about 100%. The reverse osmosis of DN and DGN membranes was investigated. The water permeability through the membranes was improved by the decrystallization reaction. DGN membranes with more than 100% grafting show high values of the salt rejection (Rs) as compared with DN and DGN membranes with about 50% grafting, especially at the region of the high hydraulic permeability coefficient of water (K). The relationships among Rs, K, and the volume fraction of water (H) are discussed by considering the results of the decrystallization reaction and electron microscopy.     

Study on radiation-induced polymerization of vinyl monomers adsorbed on inorganic substances. II. Radiation-induced polymerization of methyl methacrylate adsorbed on several inorganic substances

The radiation-induced polymerization of methyl methacrylate (MMA) absorbed on such inorganic substances as silica gel, white carbon, silicic acid anhydride, zeolite, and activated alumina was carried out to compare with the case of styrene. The rate of radiation-induced polymerization adsorbed on inorganic substances was high compared with that of radiation-induced bulk state polymerization, as was the case with styrene. Inorganic substrates which contain aluminum as a component element are more likely to be grafted than those which consist of SiO₂ alone, as with styrene. The molecular weight distribution of unextractable polymer and extractable polymer differs, depending on the type of inorganic substance. Experiments by a preirradiation method were carried out in case of silica gel, white carbon, and silicic acid anhydride. GPC spectra of the polymer obtained were different from those of polymer formed by the simultaneous irradiation method. It appears that all the unextractable polymer is grafted to the inorganic surface with chemical bond.