Shujiro Otsuki

Elucidation of dimethylsulfone metabolism in rat using a 35S radioisotope tracer method

Abstract The metabolism of dimethylsulfone was quantified for possible medical applications based on the hypothesis that the agent may be metabolized to yield methionine or its metabolites. The 35 S-labeled dimethylsulfone and methionine are orally administrated to rat. Over 80% of the administrated dimethylsulfone is metabolized in the rats tissues, and 59.7–79.1% of it is then excreted into the urine as 35 S-containing metabolites; 3.5–10.3% of the same remains incorporated in the tissues. The uptake of radioactivity, though different from the quantity of methionine in percentage at the retained site, is observed in the blood, spleen and hair, and over 80% of the administered [ 35 S] dimethylsulfone is excreted the same day. Meanwhile, the distribution of the 35 S concentrations of both agents in the rat system suggests that this compound had been metabolized to yield certain sulfur-containing compounds.

Estimation of the behaviour of hydrogen in naphthalene in pyrolysis of coal tar using tritium tracer methods

Abstract The behaviour of hydrogen in naphthalene in the pyrolysis of coal tar was investigated using a tritium tracer technique to elucidate the pyrolysis mechanism of coal tar. The pyrolysis of coal tar containing tritiated naphthalene was carried out using a batch reactor at 800–950°C for 50 sec. The ratios of amounts of naphthalene in the tars pyrolysed at 800, 900, and 950°C to that in the feed tar were 80.1, 73.4, and 42.5 wt%, respectively. However, the ratios of the radioactivity of naphthalene in tars after pyrolysis to that in the feed tar also decreased significantly with increasing temperature and it was only 12.9% for the reaction at 950°C. The ratio of the recovered radioactivity of naphthalene to the initial radioactivity of naphthalene in the feed tar was about one-third of that of the recovered amount of naphthalene to the initial amount of naphthalene in the feed tar at 950°C. The results indicated that the hydrogen in naphthalene transferred to other compounds in the pyrolysis of coal tar. It is suggested that naphthalene could play an important part in the radical reaction mechanism in the pyrolysis of coal tar.

Synthesis of polysulfides using diisobutylene, sulfur, and hydrogen sulfide over solid base catalysts

A series of solid base catalysts were prepared with several alkali and alkaline earth metal species. The catalysts were used in one-stage synthesis processes of polysulfides using diisobutylene (DIB), sulfur, and hydrogen sulfide (H 2S). The possibility of using solid base catalyst as an alternative for a liquid amine catalyst and the effects of preparation conditions on the catalytic activity were discussed. Alumina-supported potassium catalysts showed a catalytic activity comparable to that of dicyclohexylamine. The alkali metal catalysts proved to be more effective than alkaline earth metal catalysts. Further, a three-stage mechanism for polysulfide synthesis using the system of diisobutylene, sulfur, and hydrogen sulfide in the presence of solid base catalysts was suggested. Moreover, a novel [ 14 C]CO2 radioisotope pulse tracer method was developed to determine the amount of CO2 adsorption on solid base catalysts at the temperatures between 100–400 ◦ C and under 0.6–3.1 MPa. The relationship between the uptake amount of CO2 on the alkali metal catalysts and the catalytic activity in syntheses of polysulfides was discussed.