Hiroo Takagi

Reaction of ketenes with atomic oxygen

Rate constants for the reaction of atomic oxygen with ketene, and methyl, ethyl, and dimethyl ketene were measured over a temperature range of 230–449 K using the pulse radiolysis resonance absorption system. Over the temperature range of the experiments, the rate data could be fitted by Arrhenius expressions: O+CH2CO, (2.92±0.78)×10−12exp[(−1349±154 cal mol−1)/RT]; O+(CH3)CHCO, (4.79±1.31)×10−12exp[(494.9±163.2 cal mol−1)/RT]; O+(C2H5)CHCO, (5.36±0.83)×10−12exp[(444.6±94.0 cal mol−1)/RT]; O+(CH3)2CCO, (5.92±0.94)×10−12exp[(1131±85 cal mol−1)/RT]; in units of cm3 molecule−1 s−1. The rate constants at room temperature were also determined using a discharge‐flow system coupled to a photoionization mass spectrometer. Rate constants obtained are 0.043±0.04, 1.16±0.13, 1.36±0.11, and 6.04±0.64×10−11 cm−3 molecule−1 s−1 for CH2CO, (CH3)CHCO, (C2H5)CHCO, and (CH3)2CCO, respectively. Several reaction products were analyzed by the photoionization mass spectrometer.

Formation of methyl nitrite in the surface reaction of nitrogen dioxide and methanol. 1. Dark reaction

The reaction of nitrogen dioxide and methanol which has been known in the gas phase to proceed thermally as CH/sub 3/OH + 2NO/sub 2/ ..-->.. CH/sub 3/ONO + HNO/sub 3/, was found to proceed heterogeneously on various surfaces as well, in an 11-L Pyrex cell and a 6065-L evacuable smog chamber. An FTIR study has revealed that the reaction products are the same as in the homogeneous reaction, i.e., methyl nitrite and nitric acid. Neither methyl nitrate nor nitrous acid was observed. Among the surfaces studied, uncoated stainless steel, pyrex, and the smog chamber wall surfaces were found to be the most active to induce the surface reaction. The apparent activation energy of the surface reaction in the smog chamber was determined to be -11.9 +/- 3.3 kJ mol/sup -1/. 25 references, 5 figures, 4 tables.

Observation of 3-Hexene-2,5-dione in the Photooxidation of 1,2,4-Trimethylbenzene in the NO-H2 O-Air System

Abstract Formation of 3-hexene-2,5-dione (diacetylethylene) was observed in the photooxidation of 1,2,4-trimethylbenzene in the mixture of NO-H2O-air. The 3-hexene-2,5-dione is a larger aromatic ring-ruptured compound than has been reported. Although the yield of 3-hexene-2,5-dione collected was very low, the formation of 3-hexene-2,5-dione showed that the formation of other large dicarbonyl compounds due to the cleavage reaction of aromatic ring is possible in the photooxidation of aromatic hydrocarbons. Formation of 3-hexene-2,5-dione was also observed in the photooxidation of the p-xylene system.

New values of molecular extinction coefficient and specific rotation for cyanobacterial toxin cylindrospermopsin

The molecular extinction coefficient epsilon of cylindrospermopsin (CYN) purified by the anion exchange and the normal-phase HPLC procedures was determined to be 9800 at 262 nm. This epsilon is significantly higher than those (epsilon, 5800-6250) reported previously. In order to determine CYN concentrations in solutions using UV absorption, the epsilon-value of CYN should be corrected from 5800 to 9800. Further, the [alpha](D) value of CYN should be corrected from +12.5 degrees to +17.0 degrees .

Analysis of triorganotin compounds in water samples by hydrophilic interaction liquid chromatography-electrospray ionization-mass spectrometry.

Hydrophilic interaction liquid chromatography (HILIC)-electrospray ionization-mass spectrometry (ESI-MS) was evaluated for the analysis of tributyltin (TBT) and triphenyltin (TPT) in water samples. Separation was performed in isocratic mode on an Atlantis HILIC silica (2.1 mm x 150 mm, 5 microm) column with a mobile phase of acetonitrile-0.1% aqueous HCOOH (86:14, v/v) at a flow rate of 0.2 mL/min. Under optimum conditions, limits of detection for TBT and TPT were 10 and 20 pg injected onto the column, respectively. The extraction of triorganotin compounds from seawater samples was carried out using a polymer-based solid phase extraction cartridge of mixed modes with reversed-phase and weak anion exchange. Tributyltin-d(27) chloride and triphenyltin-d(15) chloride were used as internal standards. The relative standard deviations for the analysis were less than 4%. Using the proposed method, it was possible to analyze concentrations of TPT and TBT in seawater at ppt levels.

NIES certified reference material for microcystins, hepatotoxic cyclic peptide toxins from cyanobacterial blooms in eutrophic water bodies.

A certified reference material (CRM) for microcystins has been prepared by the National Institute for Environmental Studies (NIES). Microcystins are hepatotoxic cyclic peptides produced by cyanobacteria in eutrophic water bodies. At least seven microcystin variants were found by HPLC analysis of the NIES CRM, of which [Dha7]microcystin-RR and -LR were the major microcystins present. Because of the lack of available standards we determined the total microcystin concentration in the CRM by the MMPB method, and elucidated the structures of the main individual microcystin variants following their isolation. Analyses of NMR and MS spectra indicated that the remaining minor variants in the CRM were [D-Asp3, Dha7]microcystin-RR and -LR, and [Dha7]microcystin-YR, -ThTyrR, and -HilR. The CRM is valuable not only as a standard material for the quantitation of total microcystins but also for the identification of individual [Dha7]microcystin variants.

Formation of methyl nitrite in the surface reaction of nitrogen dioxide with methanol. 2. Photoenhancement

The surface reaction of NO/sub 2/ and methanol was studied in the evacuable smog chamber under the irradiation of UV-visible light (greater than or equal to 290 nm). Kinetic analysis of the gaseous reactant and products with the aid of computer modeling revealed that the surface reaction to yield CH/sub 3/ONO and HNO/sub 3/ is enhanced by the irradiation. The apparent second-order rate constant of the surface reaction increases linearly with light intensity, and the photoenhancement factor ranged from 1.8 to 5.9 for the k/sub 1/ value (primary NO/sub 2/ photolysis rate) of 0.16-0.38 min/sup -1/ and for the and methanol initial concentrations of 5 and 30 ppm, respectively. 30 references, 3 figures, 2 tables.

Microbial production and vaporization of mono-(2-ethylhexyl) phthalate from di-(2-ethylhexyl) phthalate by microorganisms inside houses.

Laboratory workers were bothered by an irritation that caused coughing during the cultivation of microorganisms that degraded di-(2-ethylhexyl) phthalate (DEHP). The authors found that mono-(2-ethylhexyl) phthalate (MEHP), a known cause of asthma, was released during the degradation of DEHP. At its highest production and vaporization rate, the amount was almost equal to that of the DEHP starting material. It appeared that transport into the atmosphere depended on its adsorption on dust particles. The authors attempted to cultivate several microorganisms from house materials, especially those composed of rotting polyvinyl chloride. And microorganisms produced MEHP in the culture medium. In addition, MEHP was produced from DEHP by several stock microorganisms. Thus, MEHP could easily be produced from DEHP by microorganisms in the environment. In Japan, there are many cases of asthma with unknown causes. If MEHP is one of causes, then preventive measures against some cases of asthma could be taken.