Hajime Sohmiya

Standardization of ultrasonic power for sonochemical reaction

Abstract The calorimetric method and the Weissler reaction were reevaluated as a means to standardize the ultrasonic power of individual ultrasonic devices. Results showed that the Weissler reaction, which can be regarded as a chemical dosimeter for measuring acoustic energy, was directly and linearly related to the calorimetrically determined ultrasonic power; the latter was independent of the volume and shape of a vessel, even if ultrasound was introduced using different devices. The additional description of either the calorimetrically determined power or the chemical yield of the Weissler reaction as one of the reaction conditions to ascertain the level of ultrasonic power in the research report is proposed.

DNA CLEAVAGE REACTION AND LINOLEIC ACID PEROXIDATION INDUCED BY TEA CATECHINS IN THE PRESENCE OF CUPRIC ION

Tea catechins with cupric ion promoted extensive DNA cleavage and fatty acid peroxidation in vitro under aerobic conditions. Neither cupric ions nor polyphenolic compounds including catechins alone induced DNA cleavage. While catalase significantly inhibited the DNA cleavage induced by catechins-Cu2+, superoxide dismutase (SOD) did not, indicating that H2O2 is probably involved in the DNA cleavage. These results suggest that the pro-oxidant property of catechins, which are generally considered to be anti-oxidants and anticarcinogens, is responsible for the O2 reducing ability of catechins catalyzed by cupric ion.

Sonochemical switching from ionic to radical pathways in the reactions of styrene and trans-β-Methylstyrene with lead tetraacetate

Abstract The reactions of styrene and trans-β-methylstyrene with lead tetraacetate in acetic acid are greatly influenced by ultrasonic irradiation to give products resulting mostly from radical chain pathways, whereas mechanical agitation gives products only from ionic processes.

Solid-state organic reactions proceeding by pulverization: Oxidation and halogenation with iodosobenzene and inorganic solid-supports

Abstract Pulverization-activation method was employed to accelerate solid-state organic reactions. Crushing and grinding of solid mixtures of hydrogen halide-treated silica gels, iodosobenzene and organic substrates in the absence of a solvent brought about smooth and rapid reactions to give halogenated and/or oxidized products in good yields. Various sulfides were smoothly converted to sulfonyl chlorides in one step in excellent yields. The surface of silica gel activated by pulverization serves as a reaction field on which reagent molecules can effectively encounter with each other.

Enantiomer recognition of organic ammonium salts by podand- and crown-type monensin amides ; new synthetic strategy for chiral receptors

Abstract Podand- and crown-types of new chiral receptors, characterized by a chiral polyether skeleton and an amide junction, were derived from naturally occurring monensin ionophore. Their chiral recognition ability was investigated by ion-selective electrode and 1H-NMR spectroscopic methods. Several podand-type monensin amides formed 1:1 complexes with chiral amine salts and exhibited excellent enantiomer selectivity. Since biological monensin and its macrocyclic derivatives were less effective for chiral recognition, a molecular combination of pseudo-cyclic monensin cavity, chiral polyether skeleton and neutral amide moiety offered high enantiomer selectivity. Chemical modification of biological monensin allowed remarkable development of new ionophoric-functions and provided an effective synthetic strategy for chiral receptors.

One-step synthesis and cation-dependent redox properties of new ‘quinonoid macrocycles’ bearing ion-binding polyether moieties

A one-step synthesis of novel macrocyclic quinonoid compounds bearing ion-binding polyether moieties, ‘quinonoid macrocycles,’ has been developed. By using an oxidative C–C coupling reaction as the ring-closure step, acyclic polyether precursors bearing hydroquinone dimethyl ether groups on both terminals were readily converted into new quinonoid macrocycles. The macrocycles obtained show characteristic cation-dependent redox properties very different from those of common quinonoid compounds. Since electrochemically reduced quinonoid macrocycles bind Li+ and other alkali metal cations more strongly than their neutral forms, their redox properties were effectively modified by adding these metal cations.

Ultrasonic acceleration of iodination of unactivated aliphatic hydrocarbons.

Iodination of unactivated aliphatic hydrocarbons with iodoform (CHI3) and solid NaOH were greatly accelerated under ultrasonic irradiation. The mechanism of the sonochemical acceleration was studied.

Mechanism of sonochemical excitation in the reactions of lead tetraacetate with some organic substrates

Abstract Strikingly contrasting positive and negative sonochemical effects were observed in the reactions of lead tetraacetate with styrene and 2-octanol, respectively. The decomposition of lead tetraacetate itself in the absence of a substrate is not accelerated by ultrasound. These results are consistent with the idea that the radical chain reaction of lead tetraacetate and styrene involves the bimolecular initiation step of the two species; under ultrasonic irradiation, styrene is excited in the gas phase of the cavity. The efficiency of the sonochemical excitation must be decisively different between the gas phase and the liquid shell of the cavity. The importance of the boiling point of a substrate involved in the radical initiation step is proposed as a hypothetical guideline in homogeneous sonochemistry.

Secondary sonochemical effect on Mo-catalyzed bromination of aromatic compounds

The Molybdate-catalyzed bromination of various aromatic compounds in the presence of KBr/H(2)O(2) in an aqueous/chloroform biphasic system occurred under ultrasonic irradiation, whereas the reaction did not take place under conventional mechanical stirring (1400 rpm). The sonochemical activation was found to be of secondary effect, attributed to lowering pH by sonolysis of CHCl(3)-H(2)O solvents mixture.

Effect of ultrasound on the reaction of trans-β-methylstyrene with lead tetraacetate

Abstract The detail of the reaction of trans-β-methylstyrene with lead tetraacetate in acetic acid was studied. The effect of ultrasonic irradiation using a horn-type reactor was examined and discussed from the viewpoint of the switching of the mechanism from mainly ionic to mainly radical.