The mechanism of copolymerization of maleic anhydride with styrene and with vinyl acetate

A nonaqueous potentiometric direct titration method was used to determine the composition diagrams for the copolymerization of maleic anhydride with styrene and with vinyl acetate in methyl ethyl ketone at 50°C. The data were analyzed using nonlinear least-squares minimization routines to fit composition equations for the terminal, penultimate, and complex models directly. The applicability of each model to both systems were evaluated statistically. The penultimate model was found to best describe both systems, although in the case of the maleic anhydride/vinyl acetate system this was only a small improvement over the terminal model. Although significant comonomer complexation occurs in both systems, the complex model did not provide statistically significant improvement in fit to the data compared with the terminal model.     

Complexation of poly(ethyleneimine) with copper(II) and nickel(II) ions in 0.5 M KNO3 solution

Complexation of poly(ethyleneimine) (PEI) with copper(II) and nickel(II) ions was studied in a 0.5M aqueous KNO₃ solution. The potentiometrically determined logarithm of the three successive formation constants (log k_J) were 8.14, 7.96, and 7.37 for Cu⁺²-PEI complexation and 6.74, 6.52, and 6.23 for Ni⁺²–PEI complexation at 25°C, according to Bjerrum's modified method. The maximum average coordination number was 3.2 for the Cu⁺²–PEI system and 3.7 for the Ni⁺²–PEI system. An entropy effect was observed in the third coordination. The wavelengths of maximum absorption of the complexes and the continuous variation method showed that at least two coordination sites of Cu⁺² ion and three coordination sites of Ni⁺² ion were occupied immediately by PEI as the solutions of PEI and the metal ions were mixed.     

Sunlight induces N epsilon-(carboxymethyl)lysine formation from glycated polylysine-iron(III) complex

Sunlight was found to strongly induce the formation of N epsilon-(carboxymethyl)lysine (CML) from glycated polylysine in the presence of Fe(III) ion. The initial step of this Fe(III)-catalyzed CML formation was noted to be similar to that of blueprint photography as was confirmed by the production of Turnbull's blue in sunlight-exposed glycated human serum albumin ferricyanide solution in the presence of Fe(III). Based on this, photoinduced oxidative C-C bond cleavage of the Amadori compound was assumed to be initiated by photochemical single electron transfer front ligand to Fe(III) in the Fe(III)-Amadori compound complex affording the Fe(II)-Amadori compound radical intermediate, which eventually yields either CML or active oxygen species. CML is thus a useful oxidative stress marker. The mechanism proposed here would explain the high accumulation of CML in lens protein and skin actinic elastosis.     

Synthesis,stability and bonding situation of tris-, bis- and mono[9-(azuleno[1,2-b]thienyl)]methyl cations

Stable tris-, bis- and mono[9-(azuleno[1,2-b]thienyl)]methyl cations (7a, 8a and 9a) and their derivatives, with a 6-isopropyl substituent on each azuleno[1,2-b]thiophene ring (7b, 8b and 9b) were prepared by the hydride abstraction reaction of the corresponding methane derivatives. The bonding situation of these compounds including the methane derivatives was examined by analysis of the 3J(H,H) values for the seven-membered ring from the 1H NMR spectra. The methane derivatives exhibited a significant alternating pattern in the 3J(H,H) values, which indicated that the pi-system of the azulene core is perturbed by the fused thiophene ring, showing a tendency towards a localized heptafulvene substructure. The 3J(H,H) values of 7b and 8b in the seven-membered ring revealed that the alternating C-C bond lengths in the azulene core still existed. The cations 9a and 9b, which exhibited nearly equal 3J(H,H) values in the seven-membered ring, exhibit the development of a delocalized tropylium substructure in the azulene core. X-ray crystal analysis of 6-isopropylazuleno[1,2-b]thiophene revealed substantial bond-length alternation in the seven-membered ring. Significant bond-length equalization in the seven-membered ring was also confirmed by the X-ray crystal analysis of 9b. The stability of these carbocations was examined by measurement of the pKR+ values and the redox potentials, which revealed that the bond-length alternation in the azulene core does not significantly affect the stability of the carbocations.     

Decomposition of diacyl peroxide—VII : Oxygen scrambling in 1-apocamphoryl peroxide and related diacyl peroxides-general remarks on the relationship between the stability of acyloxy radical and amounts of cage recombinations and ester formation in the decomposition of diacyl peroxide

Thermal decomposition of 1-apocamphoryl peroxide has been investigated in CCl₄ using the ¹⁸O-labelled peroxide. 1-Apocamphoryl peroxide is the first example which undergoes radical decomposition, carboxy-inversion and oxygen scrambling reaction between carbonyl and peroxidic O atoms in the peroxide in comparable rates. The major product of the decomposition was the inversion product, 1-apocamphoryl 1-apocamphyl carbonate (52·5%), and only a minute amount of 1-apocamphyl 1-apocamphorate (2·2%) was formed. The rates of oxygen scrambling were found to be 2·70±0·21 × 10^?6 (55°), 1·85±0·12 × 10^?1 sec^?1 (70°) and 9·33±0·18 × 10^?5 sec^?1 (84·3°) (E_a, 27·5 Kcal/mol, ΔS3, ?2·3 e.u.). The cage recombination mechanism was suggested for the oxygen scrambling and the amounts of cage recombination of 1-apocamphoryloxy radical pair were calculated as 65% (55°), 60% (70°) and 52% (84·3°). The yield of the ester and the amount of cage recombination of geminate acyloxy radical pair were rationalized in terms of the stability of acyloxy radicals formed in the cage.     

The enthalpy relaxation of amorphous Fe---Co alloys with metal-metalloid and metal-metal compositions

The enthalpy relaxation behaviour of metal-metalloid type (Fe_0.5Co_50.5)₈₃P₁₇ and metal-metal type (Fe_0.5Co_0.5) _90-Zr10 amorphous alloys was investigated with a DSC measurement. The annealing temperature (T_a) dependence of the annealing-induced reversible enthalpy relaxation evaluated with an endothermic showed the maximum at thesame T_a for the two alloys, but the magnitude of the relaxation was considerably smaller for the (Fe_0.5Co_0.5)₉₀Zr₁₀ alloy. Moreover, it was found that the amorphous (Fe_0.5Co_0.5)₉₀Zr₁₀ alloy has a larger atomic packing density and a higher activation energy of the enthalpy relaxation than the amorphous (Fe_0.5Co_0.5)₈₃P₁₇ alloy. Rhe small enthalpy relaxation and high activation energy for the amorphous (Fe_0.5Co_0.5)₉₀Zr₁₀ alloy were ascribed to the highly packed structure of the metal-metal type amorphous alloy.     

Langmuir monolayers and the transferred films of fluorinated amphiphiles containing vinyl groups

The monolayer behavior of long-chain esters of acrylic and methacrylic acids containing perfluoro or partially fluorinated carbon chains at the air/water interface was studied by surface pressure-area isotherm measurements and Brewster angle microscopy. It has been found that a minor change in the chemical structures of these fluorinated amphiphiles, such as a hydrogen substituted at the omega-position of the hydrophobic fluorocarbon tails instead of a fluorine as well as hydrophilic vinyl ester groups inserted between acrylates and methacrylates, induces a drastic change in the isotherms for the monolayers, suggesting different molecular orientation and packing in the films. The monolayers were transferred by horizontal lifting, Langmuir-Blodgett, and surface-lowering methods to give the X-, Y-, and Z-type films, respectively. These films were characterized by scanning probe microscopy, to clarify the mesoscopic surface structures of the molecular films exposed with the hydrophilic or hydrophobic moieties in air, depending upon the dipping methods. The Z-type films with the outermost surface of the fluorinated substituents were examined in relation to the frictional properties that strongly depend upon the fluorine and the hydrogen atoms at the end of the hydrophobic fluorocarbon chains, which is controllable at the atomic level.     

An in-syringe La-coprecipitation Method for the Preconcentration of Oxo-anion Forming Elements in Seawater Prior to an ICP-MS Measurement

A lanthanum (La) coprecipitation method with low sample consumption was explored for the preconcentration of oxo-anion forming elements prior to a measurement by inductively coupled plasma mass spectrometry (ICP-MS). The preconcentration procedure was composed of two main steps: (1) the formation of a coprecipitate with the lowest possible La and (2) the redissolution of target analytes with minimal use of nitric acid, and the elimination of high concentration La from the analysis sample. Each step was performed in a 25 mL-volume syringe to reduce the sample consumption and to avoid contamination from the experimental environment. Various parameters, such as the concentration and volume of La added into the sample solution, the precipitation pH, the aging time, and the volume of HNO(3) were optimized to obtain good recoveries and high detection sensitivities for V, As, Sb, and W, which could be hardly recovered by solid-phase extraction using a chelating resin. The obtained method was evaluated through the analysis of seawater reference materials (CASS-4 and NASS-5). The recoveries exceeded 80%, and the observed values were in good agreement with the certified values.