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.     

Electron spin resonance spectra observed in the course of grafting iron carbonyls on sodium-Y zeolites

The adsorption and/or decomposition pathway of Fe₂(CO)₉ or Fe₃(CO)₁₂ on hydrated or dehydrated NaY zeolites has been studied by an ESR technique. The adsorption resulted in the formation of three paramagnetic species withg _iso=2.0450, 2.0378, and 2.0016, which were attributable to Fe₃(CO)₁₁ ^–, Fe₂(CO)₈ ^–, and Fe(CO)₄ ^– anion radicals, respectively. These radicals have been suggested as intermediates in the formation of HFe₃(CO)₁₁ ^– on the hydrated NaY zeolite and Fe₃(CO)₁₂ on the dehydrated NaY zeolite.     

Structural studies of a protein using the assigned back-bone carbonyl carbon-13 NMR resonances

Several new methods to observe and assign the back-bone peptide carbonyl carbon NMR resonances of a protein have been developed and applied for Streptomyces subtilisin inhibitor. With the assigned carbonyl resonances various site-specific structural information can be obtained for virtually any site of the peptide chain. By putting those site-specific NMR parameters, including chemical shifts, rotational structures around peptide bond, and solvent accessibilities, together a new algorithm to predict the protein structures in solution has emerged.     

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.     

Experimental and Theoretical Investigations into the Paratropic Ring Current of a Porphyrin Sheet

Anomalous induced magnetic effects were observed in a directly fused square‐planar porphyrin sheet 1 , in that the protons above the center of the tetraporphyrin core were characteristically shifted downfield in the ¹H NMR spectrum. These observations suggest a rare paratropic ring‐current effect around the planar cyclooctatetraene (COT) core of 1 . To examine the spatial distribution of the induced magnetic effect, face‐to‐face dimeric complexes of porphyrin sheet 1 with bipyridyl‐type guest molecules ( G1 – G3 ) were prepared, which provided complexation‐induced shifts (CISs) of the guest molecules as a neat experimental guide to the distance dependence of the induced magnetic effects in 1 . Nucleus‐independent chemical shift (NICS) values of 1 were calculated by varying the distance of the probe from the plane of 1 . Whereas a simple bell‐type profile was estimated for the complex ( 1 )₂–( G1 )₄, the distance profiles of the CIS became increasingly flat for ( 1 )₂–( G2 )₄ and ( 1 )₂–( G3 )₄. Finally, we investigated the paratropic ring‐current effect just above the COT core of the complex 1 –( G4 )₂, which agrees well with the theoretically estimated distance‐dependent induced magnetic effect. Consequently, both experimental and theoretical studies on the complexes of porphyrin sheets with guest molecules revealed for the first time a unique distance dependence of the paratropic ring current.     

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.     

Bioactive saponins and glycosides. XVII. Inhibitory effect on gastric emptying and accelerating effect on gastrointestinal transit of tea saponins: structures of assamsaponins F, G, H, I, and J from the seeds and leaves of the tea plant

Following the investigation of assamsaponins A, B, C, D, and E, four new saponins termed assamsaponins F, G, H, and I were isolated from the seeds of the tea plant (Camellia sinensis L. var. assamica PIERRE), while assamsaponin J was isolated from its leaves. The structures of assamsaponins F-J were elucidated on the basis of chemical and physicochemical evidence and found to be 16,22-O-diacetyl-21-O-angeloyltheasapogenol E 3-O-[beta-D-galactopyranosyl (1-->2)][beta-D-glucopyranosyl(1 -->2)- alpha-L-arabinopyranosyl(1-->3)]-beta-D-glucopyranosiduronic acid, 21-O-angeloyl-22-O-acetyltheasapogenol E 3-O-[beta-D-galactopyranosyl(1--> 2)][beta-D-glucopyranosyl(1-->2)-alpha-L-arabinopyranosyl(1-->3)]- beta-D-glucopyranosiduronic acid, 21-O-angeloyl-28-O-acetyltheasapogenol E 3-O-[beta-D-galactopyranosyl(1-->2)][beta-D-glucopyranosyl(1--> 2)-alpha-L-arabinopyranosyl(1-->3)]-beta-D-glucopyranosiduronic acid, 21-O-tigloyl-28-O-acetyltheasapogenol E 3-O-[beta-D-galactopyranosyl(1--> 2)][beta-D-glucopyranosyl(1--> 2)-alpha-L-arabinopyranosyl(1-->3)]-beta-D-glucopyranosiduronic acid, and 16,21-O-diacetyl-22-O-cinnamoyltheasapogenol B 3-O-[beta-D-galactopyranosyl(l-->2)][beta-D-rhamnopyranosy(1-->2)- alpha-L-arabinopyranosyl(1-->3)]-beta-D-glucopyranosiduronic acid, respectively. The saponin mixture from the seeds of the tea plant was found to exhibit an inhibitory effect on gastric emptying and an accelerating effect on gastrointestinal transit in mice. Theasaponin E1 the principle saponin of the tea plant, showed potent activity, while theasaponin E2 showed none, so that the position of the acyl groups in the sapogenin moiety is important from a pharmacological point of view.     

Organometallic polymers containing tricarbonyl(η4-diene)-ruthenium(0) and -iron(0) as pendant groups

Vinyl ethers containing tricarbonyl(14-η⁴-1,3-pentadiene)-ruthenium(0) and -iron(0) species were prepared utilizing selective dienylation with penta-dienylpotassium and were polymerized with cationic initiators to give high molecular weight polymers. The diene-metal moieties were converted into tricarbonyl(13-η³-allyl)metal species by protonation with dry HCl. Tricarbonyl(3-allyl-14-η⁴-1,3-pentadiene)iron(0) also undergoes cationic polymerization but the presence of its isomer, tricarbonyl(3-propenyl-14-η⁴-1,3-pentadiene)iron(0) inhibits the polymerization.     

Risk attitudes for nonlinear measurable utility

This paper concerns SSB utility theory in the monetary context. It introduces a measure of risk aversion and establishes necessary and sufficient conditions for comparative risk aversion. Nonseparable decompositions of an SSB utility function that have the form (x, y)=w(x)w(y)f(x–y) are examined. Risk properties such as constant risk aversion and a delta property are shown to give specific functional forms for an SSB utility function.