Hydrogen evolution from water by use of viologen polymers as electron transfer catalyst

The behavior of viologen polymer (P-V²⁺) as an electron transfer catalyst in the reaction of hydrogen generation was studied. In the photoirradiation system, which contains triethanolamine (TEA), Ru(bpy)³⁺₃, and P-V²⁺, the amount of hydrogen evolution was less than methyl viologen (MV²⁺); P-V²⁺, however, was more effective in sodium dithionite as the electron donor and showed higher initial rates than MV²⁺.     

Emulsifier-free emulsion polymerization of tetrafluoroethylene by radiation. I. Effects of reaction conditions on the polymerization rate and polymer molecular weight

The radiation-induced emulsifier-free emulsion polymerization of tetrafluoroethylene was carried out at an initial pressure of 2–25 kg/cm², temperature of 30–110°C, and under a dose rate of 0.57 × 10⁴?3.0 × 10⁴ rad/hr. The rate of polymerization was shown to be proportional to 1.0 and 1.3 powers of the dose rate and initial pressure, respectively, and is maximal at about 70°C. The molecular weight of polytetrafluoroethylene (PTFE) lies in the range of 10⁵?10⁶, increases with reaction time in the early stage of polymerization, and is maximal at 70°C but is almost independent of the dose rate. An interesting discovery is that PTFE, a hydrophobic polymer, forms as a stable latex in the absence of emulsifier. When PTFE latex coagulates during polymerization under certain conditions, the polymerization rate decreases, probably because polymerization proceeds mainly on the polymer particle surface. The observed rate acceleration and successive increase in polymer molecular weight may be due to slow termination of propagating radicals in the rigid PTFE particles.     

π-Allyl nickel halide–oxygen system as a catalyst for polymerization of butadiene

The π-allyl nickel halide-oxygen system was found to be active as catalyst for stereospecific polymerization of butadiene. The catalyst from π-allyl nickel chloride or π-allyl nickel bromide yields the polymer of 90% cis-1,4 content with high activity, whereas the catalyst from π-allyl nickel iodide affords a polymer of 70% or less cis-1,4 content. The catalyst systems can be fractionated into two parts on the basis of solubility in benzene. It is concluded that the catalyst activity originates essentially from the benzene-insoluble nickel complex which is composed of oxygen, halogen, σ-allyl group, and nickel. The structure of growing polymer terminal is discussed in relation to the mechanism of the stereospecific polymerization.     

220-MHz NMR spectra of acrylic monomer–2-substituted 1,3-diolefin alternating copolymers

An investigation by 220-MHz NMR spectroscopy was carried out on the alternating copolymers of acrylic monomer with 2-substituted 1,3-diolefin. The chain structures were determined. The acrylic monomers used were methyl methacrylate (MMA), acrylonitrile (AN), and methacrylonitrile (MAN); isoprene (IP) and chloroprene (CLP) were the 1,3-diolefins. In the MAN–IP alternating copolymer, the 1-position methylene protons of IP showed an AB quartet peak, confirming the α-1 linkage structure. Similarly, in the MMA–CLP and AN–CLP copolymers, the 1-position methylene protons of CLP showed and AB quartet and an ABX pattern, respectively, confirming the α-1 linkage structure in both these cases also. The α-1 linkage structure was also revealed by the decoupling technique in the MAN–CLP alternating copolymer. The AN–IP and MMA–IP alternating copolymers also possess a bond between the α-position of the acrylic monomer and the 1-position of IP. The monomeric units in the alternating copolymers of acrylic monomers with 2-substituted 1,3-diolefins were generally linked at the α-position of acrylic monomer and the 1-position of 1,3-diolefin. On the other hand, in the Diels-Alder adducts of acrylic monomer with 2-substituted 1,3-diolefin, the reaction takes place between the α-position of acrylic monomer and the 4-position of 1,3-diolefin. The regioselectivity of the alternating copolymers and the Diels-Alder adducts is quite compatible with the expectations from molecular orbital theory.     

Structure and reactivity of α,β-unsaturated ethers. V. Cationic copolymerizations of ring-substituted phenyl vinyl ethers

Phenyl vinyl ether (M₁) has been copolymerized with its various ring-substituted derivatives (M₂) in toluene at ?78°C with stannic tetrachloride as catalyst. The substituents investigated include p-CH₃O, m-CH₃O, p-CH₃, m-CH₃, p-Cl, and m-Cl. The course of copolymerization was followed by gas chromatographic determinations of residual monomers, and the monomer reactivity ratios were evaluated by use of the integral form of the Mayo-Lewis copolymerization equation. Except for the unusual case of the m-CH₃O derivative, the observed values of log (1/r₁) were found to be linearly correlated with Hammett's σ constants, the reaction constant being ρ = ?1.76 with the correlation coefficient r = 0.990. Comparisons of these results with the existing data for the styrene copolymerizations have enlightened the behavior of the oxygen atom in transmitting the electronic effects of ring substituents onto the reaction center.     

Alternating copolymerization of dienes with α-olefins

Alternating copolymerization of butadiene with several α-olefins and of isoprene with propylene were investigated by using a mixture of VO(Acac)₂, Et₃Al, and Et₂AlCl as catalyst. The alternating copolymerization ability of the olefins decreases in the order, propylene > 1-butene > 4-methyl-1-pentene > 3-methyl-1-butene. The study on the sequence of the copolymer of isoprene with propylene by ozonolysis reveals that the polymer chain is reasonably expressed by the sequence \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_{\rm 2} \hbox{--} {\rm CH} \hbox{=\hskip-1pt=} {\rm C(CH}_{\rm 3}) \hbox{--} {\rm CH}_{\rm 2} \hbox{--} {\rm CH(CH}_{\rm 3}) \hbox{--} {\rm CH}_{\rm 2} \rlap{--}]_n $\end{document}. NMR and infrared spectra indicate that the chain is terminated with propylene unit, forming a structure of ?C(CH₃)? CH₂? C(CH₃)?CH₂ involving a vinylene group.     

Photo-induced dimerization of 1-naphthoxide anion: Electron transfer mechanism

Irradiation of sodium 1-naphthoxide in MeOH gave selectively 1,4-dihydro-4',8-dihydroxy-1,1'-binaphthyl 2. A similar reaction in PhH afforded the regioisomer 5, along with 6, Structural proof is presented for these hitherto unknown dimers. The reaction is completely quenched in the presence of naphthalene, a good electron scavenger. This new type of photodimerization was proved to be initiated by intermolecular electron-transfer from the excited 1-naphthoxide anion to the ground state one to give the oxidation-reduction dimers.     

Effect of dose rate on the radiation-induced polymerization of ethylene in tert-butyl alcohol

The dependence of the dose rate on the rate of radiation-induced polymerization of ethylene in tert-butyl alcohol containing 5 vol-% water was studied. The reaction was carried out by use of a reactor with a capacity of 100 ml under the following conditions: pressure, 200 kg/cm²; temperature, 24 ± 3°C; dose rate, 3.7 × 10⁴?1.6 × 10⁵ rad/hr; amount of medium, 70 ml. The dose rate exponents for rate of the polymerization, the molecular weight, and the number of polymer chain were found to be about 0.8, ?0.1, and 0.9, respectively. These results were well explained with kinetic results (obtained by a novel analytical method) for the polymerization which contain both first-order and second-order terminations for the concentrations of propagating radical. The individual values of the rate constants in each elementary reaction were also obtained.     

Optimization of the electrokinetic supercharging preconcentration for high-sensitivity microchip gel electrophoresis on a cross-geometry microchip

We developed a novel on-line preconcentration procedure for microchip gel electrophoresis (MCGE), which enables application of electrokinetic supercharging (EKS) for highly sensitive detection of DNA fragments on a cross-geometry microchip. In comparison with conventional pinched injection using the cross microchip, the present approach allows loading a much larger amount of the sample by taking advantage of a newly developed operational mode. In order to obtain high preconcentration effect and prevent splitting of an enriched sample into subchannels, i.e., off the detector range, effects of the voltage applied on the reservoirs and the time of isotachophoretic preconcentration were examined. The optimal balance between the voltage and time was found for a high-sensitivity analysis of DNA fragments. After experimental optimization the detection limit of a 150 bp fragment was as low as 0.22 mg/L (S/N = 3) that is 10 times better than using the conventional pinched injection.     

Rapid colorimetric determination of manganese in waters containing iron : A modification of the formaldoxime method

A rapid photometric method with formaldoxime is described for the determination of small amounts of manganese in waters containing iron. The iron formaldoxime formed is decomposed by addition of EDTA and hydroxylamine after development of the manganese-formaldoxime color. Beer's law holds up to 3 mg Mn/1. Up to 25 mg iron(II) or (III) per 1 can be tolerated.