Pyrolysis—gas chromatographic determination of run numbers in methyl methacrylate--styrene copolymers using the boundary effect

By considering the effect of neighbouring monomer units in depropagating polymer chain radicals on the formation of degradation products, a new boundary effect theory was developed in order to elucidate the sequence distributions in vinyl-type copolymers using the corresponding monomer yields. This theory was applied succesfully to the calculation of the sequence distributions in methyl methacrylate—styrene copolymers in terms of the run numbers. The significance of newly introduced parameters (monomer formation probability constants) is also discussed.     

Crystal structure of optically active poly(isopropylethylene oxide)

The crystal structure of optically active poly(isopropylethylene oxide) was analyzed by x-ray diffraction. Two molecular chains having twofold screw symmetry pass through an orthorhombic unit cell with parameters a = 12.85 Å, b = 7.52 Å, and c (fiber period) = 5.55 Å and space group P2₁2₁2₁-D. The crystal structure was refined by the constrained least-squares method. The molecular structure consists mainly of ?TG sequences and is very similar to the (9/4) helical structure in poly(tert-butylethylene oxide).     

Dynamic viscoelastic properties of unsintered polytetrafluoroethylene

The molecular motion of unsintered polytetrafluoroethylene (PTFE) was studied by dynamic viscoelastic measurements. From results for variously heat treated suspension polymerized (molding powder) PTFE, the following conclusions are drawn. Molding powder, as received, has a high degree of crystallinity according to calorimetric results and lower magnitude of the γ relaxation, but the behavior of the β relaxation suggests that the crystals are disordered more than those of the sintered PTFE. The β relaxation peak for an emulsion polymerized PTFE (fine powder) occurs at a higher temperature and is sharper than that for the molding powder, so that the crystals of the fine powder are better ordered than that for the molding powder. The behavior of the β relaxation for the radiation induced-polymerized PTFE is affected by polymerization conditions, particularly concentration of emulsifier. It is concluded from the results for the unsintered PTFE polymerized by various methods that the nature of crystalline state is decided during the course of simultaneous polymerization and crystallization. Molding powder as received has a relatively high magnitude of relaxation between 30°C to 180°C, but with little temperature dependence in this temperature range. This relaxation is diminished by gamma-ray irradiation. Since the molding powder has a complicated morphology, the relaxation in this temperature range is attributed to inter-particle friction rather than a relaxation associated with motion on the molecular level.     

A new echo phenomenon in laser induced population grating in gases — LIPG echo

We report the observation of a new type of echo produced by applying two intersecting light pulses with different angles (θ and θ′) at t = 0 and τ. The laser induced population grating (LIPG) created by the first excitation and degraded due to the thermal motion of atoms is reformed by the second excitation at $\text{t}{}_{\mathrm{e}}\text{=}\text{τ+mτ}\text{(αn?M)}$, where m and n are integers and $\text{α}\text{sin}\text{(}\text{θ}\text{2}\text{)=}\text{sin}\text{(}\text{θ′}\text{2}\text{)}$. The experiment was performed in the ground state $\text{3}{}^2\text{S}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ of atomic sodium vapor. This echo is not related to the atomic coherence but to the population distribution, and has novel feature for studying velocity-changing collisions.     

Chlorination of aliphatic hydrocarbons, aromatic compounds, and olefins in subcritical carbon tetrachloride

The reactions of various substrates including aliphatic hydrocarbons, aromatic compounds, and olefins were investigated in subcritical carbon tetrachloride. Ketones and sulfones were stable under the employed conditions. The coupling adducts between olefins and carbon tetrachloride were obtained from the reactions of olefins.     

Templating route for mesostructured calcium phosphates with carboxylic acid- and amine-type surfactants

Mesostructured calcium phosphates constructed by ionic frameworks were synthesized using carboxylic acid- and amine-type surfactants in mixed solvent systems of ethanol and water. A lamellar mesostructured calcium phosphate was prepared using palmitic acid as an anionic surfactant, as in the case using n-alkylamines. A wormhole-like mesostructured calcium phosphate can be obtained using dicarboxyl N-lauroyl- l-glutamic acid, whose headgroup is larger than that of palmitic acid. Similar mesostructured product was obtained using 4-dodecyldiethylenetriamine with a large headgroup containing two primary amine groups. Interactions of carboxyl and primary amino groups in the surfactant molecules with inorganic species are quite important for the formation of mesostructured calcium phosphates. The Ca/P molar ratio of mesostructured calcium phosphates was strongly affected by the molecular structure of surfactants containing carboxyl and primary amino groups. Ca-rich materials can be obtained using carboxylic acid-type surfactants (Ca/P approximately 1.7) rather than amine-type surfactants (Ca/P approximately 1.0).     

Synthesis of substituted benzenes and phenols by ring-closing olefin metathesis

New synthetic approaches to substituted aromatic compounds are reported. Ring-closing olefin metathesis (RCM)/dehydration and RCM/tautomerization are the key processes in the synthesis of substituted benzenes 3 and phenols 6, respectively. Readily accessible 1,5,7-trien-4-ols 7, which are the precursors of benzenes, were prepared from beta-halo-alpha,beta-unsaturated aldehydes 11 or beta-halo-alpha,beta-unsaturated esters 19 by utilizing reliable transformations in which cross-coupling with vinylic metal reagents 12 and allylation with allylic metal reagents 13 were employed as carbon-carbon bond forming reactions. RCM of 7, followed by dehydration, afforded a wide variety of substituted benzenes 3. In addition, RCM of 1,5,7-trien-4-ones 9, which were prepared by oxidation of 7, furnished various substituted phenols 6 by automatic tautomerization.     

Preparation of fritless capillary using avidin immobilized magnetic particles for electrochromatographic chiral separation

In capillary electrochromatography (CEC), magnetic particles (MPs) were packed in a fused silica capillary by using the magnetic field to be retained without frits. For a chiral CEC separation, avidin was immobilized onto the surface of the MPs (AVI-MPs) as a stationary phase by using the physical adsorption technique. The injected AVI-MPs into the capillary were stably captured with the magnet (surface magnetic flux density, 250 mT) under the separation voltage of 10 kV (190 V/cm). By employing the fritless AVI-MPs packed capillary, the chiral separation of ketoprofen was successfully attained with the packing length of only 5 cm. Effects of the modification condition of avidin, pH of background solution, and the packing length on the enantioseparation were also investigated. Under the optimal condition, furthermore, the repeatability for the retention time of ketoprofen was better than 1.5% in the relative standard deviation and the capillary-to-capillary reproducibility was also acceptable in the prepared fritless capillaries.     

t-Bu-QuinoxP* ligand: applications in asymmetric Pd-catalyzed allylic substitution and Ru-catalyzed hydrogenation

The potential of the t-Bu-QuinoxP* ligand (1) as a chiral ligand in asymmetric synthesis was examined. The ligand exhibited good to excellent asymmetric induction in Pd-catalyzed asymmetric allylic substitution of 1,3-diphenyl-2-propenyl acetate (up to 98.7% ee) and in Ru-catalyzed asymmetric hydrogenation of ketones (up to 99.9% ee).