Photodegradation of some ethylene-norbornene random copolymers

We investigated the photodegradation of specific ethylene-norbornene random copolymers (ENRC) - a group of substances which has been attracting much attention in recent years. ENRCs having various contents of norbornene were studied. After irradiation, each sample was separated into chloroform-insoluble and soluble portions. The chloroform-insoluble portion was weighed and analyzed by FTIR. The chloroform-soluble portion was analyzed by size elimination chromatography (SEC), FTIR and ¹H NMR. The yield of the chloroform-insoluble portion increased with increased irradiation time. Formyl, formate, acyl, hydroxy groups and a carbon-carbon double bond were formed by photo-irradiation. Apparently, hydrogen atoms bound to the tertiary and secondary carbon atom in the parent ENRCs are abstracted. From these results, it is suggested that auto-oxidation results from photo-irradiation of the ENRCs. In ENRCs with similar stereoregularity, the degree of photodegradation increases with increasing norbornene content.     

The salt-induced sphere-rod transition of micelles of dodecylpyridinium iodide in aqueous NaI solutions

Static light scattering has been measured on aqueous NaI solutions of dodecylpyridinium iodide (DPI) over NaI concentrations from 0 to 0.05 M. Reduced intensity of scattered light increases with increasing DPI concentration above the critical micelle concentration. The Debye plot is generally a curve with an initially positive slope and with a weakly convex, upward curvature, when the NaI concentration ranges from 0 to 0.005 M. The molecular weight of the spherical micelle of DPI is 28400 in water, and it increases slightly with increasing NaI concentration. The initial slope decreases with increasing NaI concentration and changes from positive to negative across 0.007 M NaI, which is the threshold for the sphere-rod transition and where the micelle has a molecular weight of 34400. At NaI concentrations from 0.01 to 0.05 M, the Debye plot is a curve with an initially negative slope and with a convex, downward curvature. The magnitudes of slope and curvature are larger, and the rodlike micelles of DPI have larger molecular weight and stronger mutual interaction, as the NaI concentration increases. The linear double logarithmic relationship between molecular weight and ionic strength holds for spherical and rodlike micelles, respectively.     

Effect of o-methyl group on rate, mechanism, and resonance contribution: aminolysis of Y-substituted phenyl X-substituted 2-methylbenzoates

Second-order rate constants have been determined spectrophotometrically for the reactions of 4-nitrophenyl X-substituted 2-methylbenzoates (2a-e) and Y-substituted phenyl 2-methylbenzoates (3a-e) with alicyclic secondary amines in 80 mol % H(2)O/20 mol % DMSO at 25.0 +/- 0.1 degrees C. The o-methyl group in the benzoyl moiety of 2a-e retards the reaction rate but does not influence the reaction mechanism. The Hammett plots for the reactions of 2a-e are nonlinear, while the corresponding Yukawa-Tsuno plots are linear with large r values (1.06-1.70). The linear Yukawa-Tsuno plots suggest that stabilization of the ground-state through resonance interaction between the electron donating substituent X and the carbonyl group is responsible for the nonlinear Hammett plots, while the large r values imply that the ground-state resonance interaction is significant. The reactions of 2a-e resulted in smaller rho(X) values but larger r values than the corresponding reactions of 4-nitrophenyl X-substituted benzoates (1a-e). The small rho(X) value for the reactions of 2a-e (e.g., rho(X) = 0.22) is suggested to be responsible for the large r value (e.g., r = 1.70). The reactions of 3a-e with piperidine are proposed to proceed in a stepwise manner with a change in the rate-determining step on the basis of the curved Br?nsted-type plot obtained. Microscopic rate constants associated with the reactions of 3a-e are also consistent with the proposed mechanism.     

Effect of Solvent Diols and Ligands on the Properties of Sol-Gel Alumina-Silicas

Amorphous alumina-silicas were prepared from a tetra-alkoxysilane and anhydrous aluminum trichloride or an aluminum alkoxide by a sol-gel process using 2-methyl-2,4-pentanediol, pinacol, 1,2-propanediol, 2,3-butanediol or ethylene glycol as the solvent or complexing agent, and the effect of diols and alkoxy groups on the physical and chemical properties of the alumina-silicas was examined. When the diol or the alkoxy group was bulky, the alumina-silicas had relatively larger micropores, a larger pore volume and higher surface areas. In the conversion of methanol catalyzed by the alumina-silicas, the bulkier diols and alkoxides gave catalysts that produced dimethyl ether in higher yield and hydrocarbons in lower yield. Thus, when ethylene glycol was used as the diol, the best catalyst for the production of hydrocarbons, especially the production of olefins such as ethylene, propylene and butene, was obtained. Furthermore, in comparison with alumina-silica prepared by a traditional kneading process, it was found that the sol-gel alumina-silica could efficiently convert methanol to dimethyl ether and hydrocarbons, but the material prepared by kneading had a very low conversion of methanol to other compounds.     

Synthesis and polymerization of N-[1-(1-substituted-2-oxopropyl)]acrylamides and -methacrylamides. copolymerization of these monomers with styrene and substituent effects

The synthesis and polymerization of N-[1-(1-substituted-2-oxopropyl)]acrylamides and -methacrylamides are described. Seven new monomers were prepared by two kinds of synthetic procedure. The polymerization of these monomers was carried out. Monomer reactivity ratios in the polymerization of these monomers with styrene were determined and the Alfrey-Price Q and e values calculated. The effects of substituents on the reactivities in copolymerization were observed, and an interpretation of the results is given.     

A facile synthesis of fused spiroketal skeleton: 2,2′-spirobi(4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydrochroman)

A one-pot synthesis of fused spiroketal skeleton, 2,2′-spirobi(4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydrochroman) 4a-c, has been achieved for the first time by an application of Michael reaction between dimedone (5,5-dimethylcyclohexan-1,3-dione) 1 and trans,trans-diarylideneacetone (1,5-diaryl-1,4-pentadien-3-one) 2 using anhydrous ZnCl₂ as catalyst. The spiroketalization was achieved efficiently via intramolecular cyclization of the Michael 1:2 adduct.     

A Novel Layered Silicate with a Helical Morphology

Helices composed of stacked layers are present in the novel silicate obtained from a silica sol and NaOH by hydrothermal synthesis in the presence of tetramethylammonium (TMA) hydroxide and 1,4-dioxane. The helical morphology is evident in scanning electron micrographs (see picture). The TMA and sodium ions of the silicate are readily replaced by protons, and on heating to 200°C a reversible phase transition occurs in which water molecules are lost from between the layers.     

Preparation of Titania Containing Mixed Oxides and Their Catalytic Activities

Titania containing catalysts were prepared by conventional procedures (coprecipitation, hydrogel kneading and titania precipitation) and a complexing-agent assisted sol-gel method. The effect of preparation methods on their properties and catalytic activities in the oxidation of olefins and decomposition of cumene hydroperoxide were examined. The sol-gel method gave the best dispersion of titania. In contrast, with the kneading and titania precipitation method, titania formed crystalline particles. The sol-gel catalysts are more effective for epoxydation of olefins because of the high dispersibility of Ti in them. However, the most active catalysts in the decomposition of cumene hydroperoxide are kneading ones.     

N,N′,N″—三(对—甲苯磺酰基)二亚乙基三胺的合成

二亚乙基三胺与对—甲苯磺酰氯在碳酸钾存在下,发生对甲苯磺酰化反应,生成N,N′,N″-三(对—甲苯磺酰基)二亚乙基三胺,产率96％。考察影响反应的几个因素。