Non-destructive rapid analysis of brominated flame retardants in electrical and electronic equipment using Raman spectroscopy.

Using Raman spectroscopy without any preparation, we analyzed the brominated flame retardant, polybromodiphenyl ethers (PBDEs), which has been prohibited by the European Union. The typical Raman bands of PBDEs, which are clearly different from those of other brominated flame retardants, are from 100 to 300 cm(-1). In our analysis, the detection limit was about 100 ppm, and the analysis took about 1 min, whereas the usual method of solvent extraction using gas chromatography/mass spectroscopy takes 50 h.     

A new route for the construction of the AB-ring core of Taxol

A new method for the construction of the AB-ring core of Taxol was developed utilizing a new skeletal transformation protocol as a pivotal step. The acid-catalyzed rearrangement of the cyclopentenone-allene photoadduct gave a bridged seven-membered ketone, which was easily transformed, using the intramolecular Suzuki reaction and the oxidative cleavage of the vicinal diol, to the bicyclic diketone.     

Effect of structural variation within cationic azo-surfactant upon photoresponsive function in aqueous solution

The cationic azo-surfactants possessing different spacers and tail alkyl chain lengths have been synthesized by azocoupling ofp-alkylaniline orop-ethoxyaniline with phenol, followed by alkylation and quaternalization with dibromoalkane and trimethylamine, respectively. These surfactants showed a good solubility in water. A reversibletrans-cis isomerization of the azosurfactants by photoirradiation was assessed by UV-Vis absorption spectra. Due to a difference in HLB between thetrans- andcis-surfactants, the observed critical micelle concentration (CMC) values and the electric conductivity of the surfactant solution at above the CMC were significantly affected by the photoinducedtrans-cis isomerization. The azo-surfactants bearing moderate alkyl chain lengths such as surfactants 6 (R₂=C₂H₄, R₃=C₄H₉) and 9 (R₂=C₄H₈, R₃=C₂H₅) were found to be effective to achieve large CMC changes (3.6 mmol/L for 6 and 5.9 mmol/L for 9) by UV-light irradiation. The replacement of the tail chain species also affected the photoresponsive function. The surfactant 12, possessingp-ethoxy group as the tail chain, was found to form a stable micelle aggregation as compared with the structurally related surfactant 10 having ethyl unit as its tail group, but it exhibited a large CMC change (5.3 mmol/L) by UV-light irradiation.     

Development of dynamic compartment model for prediction of behavior of radioiodine in rice paddy field

For the assessment of a public impact caused by radionuclides released from nuclear facilities, a dynamic compartment model was developed for prediction of behavior of radioiodine in air, paddy field and rice plant system. The transfer coefficients among compartments were determined by some experimental data and assumptions for each chemical form of iodine. A verification of the model was carried out by some case studies.     

Stereoselective synthesis of tetrasubstituted (Z)-alkenes from aryl alkyl ketones utilizing the Horner-Wadsworth-Emmons reaction

Tetrasubstituted (Z)-alkenes were readily prepared through the Horner-Wadsworth-Emmons reactions of methyl 2-[bis(2,2,2-trifluoroethyl)phosphono]propionate with aryl alkyl ketones by employing Sn(OSO(2)CF(3))(2) and N-ethylpiperidine.     

Cascade Rearrangement of 5-Cyclopentylidenecyclooctanones

Acid-catalyzed rearrangement of 5-cyclopentylidenecyclooctanone derivatives 9a-c was examined to obtain polyspiropolyquinanes 11a-c, considered to have a unique helical structure, through cascade rearrangement pathways consisting of continuous transannular cyclization followed by successive 1,2-alkyl shifts. The substrates were prepared easily by use of the Wittig or McMurry reaction. Reaction of the 5-cyclopentylidenecyclooctanone (9a) with acid gave the expected dispirotriquinane ketone 11a in high yield. The precise mechanism was elucidated by a deuterium-labeling experiment. In the case of the ketone 9b, having another spiroannulated cyclopentane ring attached on 9a, the trispirotetraquiane 11b was not obtained but the bis-propellane-type tetrahydrofuran 25 was produced exclusively. The 5-(5'-cyclopentylidenecyclooctylidene)cyclooctanone (9c) afforded the polycyclic compounds 27-31, depending on the acid used, instead of the desired tetraspiropentaquinane 11c. The structures of the products were determined by NMR spectral data including 2D (13)C INADEQUATE spectra and X-ray crystallographic analyses. The unexpected rearrangement pathways are also discussed.     

Oscillating frequency of piezoelectric quartz crystal in solutions

Oscillating frequencies of a piezoelectric crystal were measured in various solutions. One side of the crystal surface was coated with a silicon sealant. This coating was useful for measuring the oscillation of crystals in solutions for a wide range of products of density (?) and viscosity (η) and in electrolyte solutions. For measurement in solutions, the frequency change depended on the circuit used, whereas for measurements in air the circuit did not influence the frequency change. All experimental data showed that the frequency change from pure water, ΔF_w, followed ΔF_w = ? K(√?η ? √?_wη_w) except for electrolyte and polymer solutions, where K is a proportionality constant, η_w the density of pure water and η_w the viscosity of water.     

Quartz crystal microbalance immunosensor for highly sensitive 2,3,7,8-tetrachlorodibenzo-p-dioxin detection in fly ash from municipal solid waste incinerators

A quartz crystal microbalance (QCM) immunosensor was developed for the detection of 2,3,7,8-tetrachlorodibenzo-p-dioxins (TCDD) in environmental pollutants. An anti-TCDD antibody was immobilized on the gold surface of the QCM via chemical coupling, and its immunologic activity was then maintained by treatment with an artificial stabilizing reagent such as poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate). A competitive immunoreaction with TCDD conjugated ovalbumin (TCDD-ovalbumin) was used to detect TCDD. A calibration curve was obtained through the competitive immunoreaction, and linearity was shown from 100 ng mL(-1) to 0.1 ng mL(-1). Also, the cross-reactivities of the anti-TCDD monoclonal antibody were thoroughly evaluated with several TCDD derivatives. The relationships between GC-MS, ELISA, and QCM were compared using fly ash samples from a municipal solid waste, which were prepared using an accelerated solvent extractor. For 23 samples, the experimental relationship between the TCDD concentration by QCM vs. the TCDD concentration by ELISA was y= 1.07x + 2.70, r= 0.99, and the TCDD concentration by QCM vs. the toxic equivalent quantity (TEQ) value by GC-MS was y= 2.46x - 14.98, r= 0.89.     

Total synthesis of (-)-stevastelin B

The total synthesis and an unambiguous structure confirmation of stevastelin B 1, a novel 15-membered cyclic depsipeptide, are described; the fatty acid moiety in 1, prepared stereoselectively from L-quebrachitol was converted into the amino carboxylic acid, whose macrolactamization by Shioiri's procedure effectively constructed the cyclic structure of 1.