The ultrasound techniques are widely useful to study the physical properties of solid, liquid and gas. The chain dynamics in polymer solutions and the interaction between polymer chains and solvents have been investigated by measuring the sound absorption and velocity. It is well known that irradiation of the ultrasound with the high intensity in the frequency range from 20 kHz to a few MHz produces cavitation bubbles in liquids and solutions. The local reaction field at the high temperature and pressure (the hot spot) is formed when the bubbles collapse. Application of the power ultrasound to polymer solution has been examined by many workers. The session of polymer chains under sonication is of interest in connection with controlling the molecular weight. The degradation has been studied by the viscosity measurement and gel permeation chromatograph. These results revealed that the ultrasonic irradiation to polymer solutions results in the decrease of the solution viscosity and the molecular weight. The long time ultrasonic irradiation gives rise to the low molecular weight(a few thousands) and the narrow polydispersity samples. The results of the ultrasonic degradation of water-soluble polymers are given in this paper. The degradation mechanism is well interpreted by the Glynn's model. They indicated that ultrasonic degradation proceeded with a certain degradation probability. The water-soluble polymers degrade with a Gaussian probability and the degradation rate depends on the molecular structure and flexibility of the polymers. At the local reaction field in monomer and polymer solutions produced by the ultrasound, monomer and polymer radicals (or others) are formed, and polymerization is initiated. Up to date, ultrasonic polymerization has been studied for various systems, such as monomer, monomer and polymer, and polymer and polymer systems. One of useful advantages in ultrasonic polymerization is that polymerization proceeds without the initiators. Recent results are reported here concerning the frequency effect on polymerization of styrene under sonication which was carried out at a constant ultrasonic intensity measured by chemical dosimeter. It is indicated that there is an optimum frequency in the range from 92 to 518kHz for effective polymerization. Effect of sonication on autopolymerization of styrene in the presence of 2,2,6,6-tetramethylpiperidinyl-1-oxy(TEMPO) as the mediating radical will be reported. The thermal polymerization under sonication proceeds in the manner of a "living" radical polymerization to afford well-defined polystyrene.

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Iron (II) hydroxide was oxidized in an ultrasonic-activated solution to produce α-FeOOH (goethite) or Fe_3O_4 (magnetite). This process involves the dissolution of Fe(OH)_2, the oxidation of Fe^<2+> to Fe^<3+>, and the precipitation of the products. It was found that the ultrasonic treatment greatly fasten the appearance and the growth of the products if oxygen was sufficiently supplied. When the oxygen supply was insufficient, on the other hand, an obvious phenomenon of sonochemical switching due to the enhanced oxidation was observed; that is, ultrasound promoted the α-FeOOH formation and suppressed the formation of Fe_3O_4 which has lower oxidation number (Fe=+8/3) than α-FeOOH (Fe=+3).

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Noble metal ions, NaAuCl_4 (Au(III)), PdCl_2 (Pd(II)) are reduced to form metallic nanoparticles by the sonication in the presence of surfactants, such as polyethylene glycol monostearate (PEG-MS; nonionic) and sodium dodecylsulfate (SDS; anionic). It is found that colloidal Pd can be isolated from coexisting Pd ions without any morphological change by the treatment of an anion exchange resin. This makes possible TEM observation of the Pd particles at desired reaction time without disturbance of Pd ions during the process of particle formation, which is an important subject for colloid chemistry but has not been so abundantly investigated. In the case of Pd(II)/ SDS, the size of Pd particles in the initial stage of the growing process (1.5 min sonication) is 4.2 nm and the number of the particles is 6.8×10^<14>. In the middle stage (6 min sonication), the size of particles is enlarged to 6.0 nm with the number of 7.7×10^<14>. In the final stage, where ions are completely reduced by 15 min sonication, the size of particles is 7.0 nm and the number of particles is 7.5×10^<14>. The unaltered number of particles at every stage suggest that the nucleation rate of Pd(0) is roughly equal to the coagulation rate of Pd particles in SDS. Smaller size of 4.4 nm is observed in PEG-MS surfactant. In gamma irradiation experiments, the sizes of particles are larger than those formed in sonication both SDS and PEG-MS.

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Permanganate ions in aqueous solutions were reduced to form manganese dioxide nanoparticles by the sonochemical method. The processes of the sonochemical reduction were monitored by the spectroscopic method. The reduction rates were accelerated in the presence of polymers or surfactants, but the formed colloidal dispersions become to be less stable. Colloidal dispersions of manganese dioxide in pure water were stable more than several months. This result gave the different trend from the case of noble metal nanoparticles. Characterization of the synthesized nanoparticles was carried out by electron microscopy observation. The average particle size was about 14 nm when the initial concentration of potassium permanganate was 0.1 mM.

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Effect of fluid motion on a sonochemical reaction field is studied through measurements of multibubble sonoluminescence. A rectangular vessel with six Langevin-type transducers was used; four transducers were attached to the bottom and two to the facing side walls. The vessel was connected to an external cooling-water circulator. The intensity of sonoluminescence (SL) from air-saturated distilled water in the vessel was measured while changing the power applied to the ultrasonic transducers with and without water circulation. Behavior of the cavitation bubbles was also observed. To compare the effect of stirring operation with that of circulation of the fluid, the intensity of both SL and sonochemical luminescence (SCL) from a luminol solution in a glass beaker, which was set into the vessel filled with degassed distilled water, was measured for various rotational speed of a stirrer. The effect of circulation on SL was similar to that of stirring. The fluid motion causes cavitation-bubble size to reduce because of diffusion of bubble nucleation. Therefore the number of the bubbles attracted to the pressure antinodes by acoustic radiation pressure increased, which were repulsed without fluid motion. Both the SL and the SCL intensity increased with increasing rotational speed of the stirrer in the high ultrasonic power range, although it decreased in low ultrasonic power range. The increase of the SCL intensity was more remarkable than that of SL in high power range. The increase rate of SCL intensity by stirring at low frequency was larger than that at high frequency in the low ultrasonic power range. These confirm the existence of an optimal fluid motion for a sonochemical reaction in connection with ultrasonic power and frequency.

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Influence of ambient pressure on multibubble sonoluminescence is studied experimentally through the measurements of time dependence of sonoluminescence intensity and time variation of oxygen content in a luminol solution to accomplish high efficiency in chemical reactions. As irradiation time of ultrasound passes at atmospheric case, the intensity increases and decreases monotonously after showing the maximum, while the oxygen content decreases all the way. The intensity and oxygen content at subatmospheric case show the similar changes to the atmospheric ones except that decrease in oxygen content is sharper. From these measurements on the condition of the constant ultrasonic frequency and constant amplitude of sound pressure, it is shown that the intensity of sonoluminescence is higher at reduced case rather than the atmospheric case on the initial irradiation of ultrasound. Also, it is found that there is an appropriate oxygen content to produce the highest intensity of the luminescence.

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Computer simulations of bubble collapses are performed under conditions of multibubble sonoluminescence for various acoustic amplitude(p_a) and the ambient bubble radius (R_0). The bubble temperature at the collapse is plotted on the R_0-p_a phase space. For experiments using a horn immersed into water, bubbles move in the R_0-p_a phase space from the upper part of Fig.1 to the lower part because bubbles created near the horn tip flow away from the horn tip where the acoustic amplitude is large. It is seen in Fig.l that the bubble temperature at the collapse is almost constant from 10 bar to 5 bar(7,000 K). It is why a single temperature can be determined for each experiment of multibubble sonoluminescence by the shape of the metal emission lines or by the chemical rate thermometry. For experiments using a standing wave of ultrasound in water, bubbles move in p_a-R_0 space from the lower part of Fig.2 to the upper part because bubbles move by the Bjerknes force toward the pressure antinode. However, bubbles can not enter into the region above the thick line because the direction of the Bjerknes force is reversed at the thick line. Thus in this case, SBSL like bubbles can be observed as seen in Fig.2.

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The ultrasound technique was applied to the synthesis of layered double hydroxides (LDH; Mg_xAl_y(OH)_<2(x+y)>CO_3^<2->_<y/2>mH_2O). The effect of the ultrasound on the synthesis of the compounds was studied in terms of crystal quality, metal composition (M^<2+>/M^<3+>) and surface property of the synthesized compounds. The crystal qualities of the compounds synthesized with ultrasound were compared with those of compounds synthesized without ultrasound to elucidate the effect of the ultrasound on the synthesis. The effect of the crystal quality on the water treatment performance was also examined from a viewpoint of removal of organic compound from water using humic substances as adsorbate. The compounds synthesized under ultrasonic conditions showed high crystal quality within a few minutes of treatment and large adsorption capacity for humic substances. The molar ratio of metal cations (M^<2+>/M^<3+>) and specific surface area were increased with increase in the treatment. The amount of the adsorption was well correlated with the crystal quality of the compounds. Ultrasound was found effective in the synthesis of highly crystallized layered double hydroxide with a few minutes of application. It enables the synthesis of the compound simply and rapidly under atmospheric conditions. The crystallite size of the compound increases with increasing the application time and power of ultrasound. The adsorption capacity of the compound for humic substances increases with increasing crystal quality of the compounds.

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Longitudinal and transverse wave velocities, elastic parameter (elastic constants, Debye temperature and Gruneisen parameter), and dilational and shear internal frictions were simultaneously observed between room temperature and 137 K for an anthracene (C_<14>H_<10>) single crystal with lattice imperfections such as vacancy and dislocation, using an ultrasonic pulse method with 1.7 MHz. The transverse wave velocity and Debye temperature dropped suddenly at 266 K, and then increased somewhat down, to 197 K, and gradually increased with decreasing temperature. The Gruneisen parameter showed two large positive peaks at 194 K and 175 K, and one large negative peak at 261 K, indicating lattice expansion and shrinkage, respectively. The dilational friction showed one small jump at 266 K and one large peak at 181K. The 266 K jump and the 181 K peak are probably due to rotation between interplanar stacks and intermolecular readjustment. The 181 K valley is due to the accumulation of strain. We also observed devitrification, shrinkage of 0.86 % and partial collapse after measurement. These results suggest a possibility of a type I/type II phase transition at 181K, caused by cooling and/or ultrasonic vibration. Thus, we can semi-quantitatively explain the low-temperature elastic anomalies of ASC, using linear chain and double potential models based on van der Waals and Lennard-Jones interactions, respectively. If no previous precise measurements of phonon velocities, VI and Vt, for organic crystals has been done, we are delighted to be pioneers in this field.

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Palladium metal was deposited sonochemically from the aqueous solution of palladium(II) chloride by the sonication using the ultrasonic homogenizer(20 kHz, 60W). The effect of some organic additives such as various kinds of alcohols and organic acids, which have high reactivity with OH radicals, on the metal deposition yield was examined. Addition of alcohols enhanced the metal deposition, the efficiency being in the order of 1,1-dimethylethanol(tert-butyl alcohol), 2-propanol, 1-propanol, ethanol and methanol, while formic acid and acetic acid gave little effect. It was found that the efficiency depended on the hydrophobicity ratio of the solute(ratio of number of hydrophobic to hydrophylic groups in a molecule), which was pointed out by Henglein. The same dependence was found for the sonochemical formation of hydrogen gas from the aqueous solutions of these additives without containing palladium ions, the higher hydrophobicity of the solute, the higher yield of hydrogen. These results were interpreted in terms of an accumulation of solute molecules at the liquid-gas interface of the cabitation bubbles, where the solute molecules scavenged the OH radicals and suppressed the recombination of OH radicals with H radicals. These radicals were generated from the sonolysis of water in the cabities. The H radicals that would otherwise recombine dimerise to hydrogen and react with palladium ions if in the presence of palladium ions in the solution. The increase of the palladium deposition and the compatible decrease of hydrogen formation with the increase of the initial concentration of palladium chloride were found in the sonolysis of aqueous 2-propanol solutions (52 mmol dm^<-3>). These results indicate the occurrence of the competitive reaction of H radical with its dimerization and the palladium ion reduction. The similar experiments were performed for hexachloroplatinic acid(IV) solutions, however, different results from those of palladium solutions were obtained.

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Acoustic cavitation is a typical non-thermal phenomenon induced in liquids and biotissues exposed to ultrasound. Its effects may be useful for therapeutic purposes if properly controlled. Techniques for promotion and suppression of acoustic cavitation will provide such controlling methods. As chemicals for reducing cavitation threshold, we previously reported that certain photosensitizers, such as rose bengal, in xanthene family are effective both in water and mouse liver. One of our research targets is applying these chemicals to cancer treatment. However, such xanthenes have poor affinities with tumor tissues. Some of porphyrins, another photosensitizer family, are known to show high affinities with tumor tissues. It has been proposed that their amphiphilicity is a factor int these high affinities. As an approach to obtain xanthenes with improved affinities with tumor tissues, we synthesized amphiphilic rose bengal derivatives. Three kinds of derivatives with incorporated alkyl groups (carbon numbers: 7-15) as the lipophilic group and carboxilic group as the hydrophilic group were synthesized. One of the families in synthesized derivatives was found to be amphiphilic and they reduced cavitation threshold in water about as much as rose bengal do. The derivatives also showed significantly increased affinities with subcutaneously-implanted murine tumor tissues.

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Mechanical or chemical effects obtained through the ultrasonic cavitation phenomenon have been applied to many industrial fields. Those effects are induced by vibration or cllapse of microbubbles in liquids. In order to obtain efficient cavitation effects, it is necessary to generate pressure larger than the cavitation threshold. In general, standing wave fields are utilized for generating the cavitation. In standing wave fields, however, cavitating bobbles are mainly located at the loops of the pressure, that causes the spatial ununiformity of cavitational effects. Moreover, the microbubbles in liquids and the free reflectional surfaces of liquids disturb the standing wave fields and prevent keeping stable cavitational fields. In this study, we propose generating the cavitation by using the squeeze-film effect which is a phenomenon that large pressure is produced into the thin liquid film between two surfaces when the surfaces approch rapidly each other. With the effect, cavitational fields can be obtained two features; spatial uniformity and temporal stabilization. The former property is due to almost uniform pressure distribution and the latter is because the change in acoustical load caused by cavitating bubbles less affects the sound field with the squeeze-film effect than ordinary standing wave field. We this time demonstrate a water treatment system utilizing the squeeze-film effect. In preliminary experiments, inactivation of cryptosporidium oosysts in water was achieved with the system.

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Thiols are well known to be oxidized by ultrasonic irradiation in an aqueous solution. In order to clarify the effects of heterogeneity on sonochemical reactions in liquid-liquid systems, disappearance reactions of thiols were studied in some water-organic solvent systems. In a c-hexane/water system, the rate constants of sonochemical disappearance reactions of alkyl thiols with long carbon chains, alkyl thiols with short ones, and p-toluene thiol were decreased in this order (Fig.2). However, in a di-i-propyl ether/water system, the order was reversed (Fig.3). In i-propanol/water systems, the rate constants of sonochemical disappearance reactions depended on the content of water and chemical structures of thiols. As shown in Fig. 4 and 5, the rate constants of alkyl thiols with short carbon chains were steeply increased as the content of water went up to over 3:8 (i-propanol:water), while that of p - toluene thiol was slowly increased. From these studies, it is concluded sonochemical organic reactions in liquid- liquid systems more greatly depend on the heterogeneity and chemical structures of substrates compared to homogeneous organic reactions.

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Sono-catalytic decomposition of water was carried out using catalysts. Sono-catalytic system is the hybrid one of sonochemical and catalytic reactions. In present paper, ultrasonic irradiation effect on homogeneous catalytic system is shown. For instance, overall water splitting was performed by sono-catalytic method using FeNH4(SO2)2 homogenous system. Liquid water was hardly decomposed to H2 and 02 but to H2 and H2O2 by sonolysis. Hydrogen peroxide can be decompose to oxygen by catalysis using a few kind of catalysts such as MnO2. Only one of them was effective. Hydrogen and oxygen are obtained from water stoichiometrically and continuously by addition of FeNH4(SO4)2. In general, when a material is added to water, the reactivity decreases with increasing concentration of impurities. The influence of additives, however, was negligible at low concentration.

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Various phenols substituted with methyl and methoxy groups were reacted with silica gel (230-400 mesh) and aluminium trichroride under ultrasonic irradiation(Sus-4005C, 50W, 40kHz) for 30 min-1h to give the corresponding alkoxy compounds in good yields. Trimethylhydroquinone in various alcohols was treated under ultrasonic irradiation with anhydrous aluminium trichloride for 30 min to give the corresponding 4-alkoxy-2,3,6- trimethylphenol in high yield. Using t-butanol as solvent, only the starting material was recopvered. From these result, the reaction mechanisms are thought as follows. The intermediary aluminium alkoxides were attacked by trimethylhydroquinone to produce the alkoxy phenols. The bulky aluminium alkoxides produced from sterically hindered alcohols were difficult to be attacked by trimethylhydroquinone, which is seen in the yields of the case of t-BuOH, i-AmOH and i-PrOH.[table]

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Although it has been known that ultrasonic cavitation induces reversible or irreversible cellular damage, the mechanism of apoptosis induced by ultrasound is still unclear. In this study, the effects of dissolved gases and an echo contrast agent, Levovist, on apoptosis induced by ultrasound were investigated. (Materials and Methods) Human histiocytic lymphoma U937 cells were maintained in RPMI 1640 culture medium containing 10% fetal calf serum. Sample solutions (3.5 ml) in polystyrene culture tubes were irradiated with continuous ultrasound at a frequency of 1 MHz and an intensity of 4.9 W/cm^2 (ISPTA). During sonication, the tubes were rotated at 30 rpm and the coupling water was maintained at 20℃. Apoptosis was examined by flow cytometry and fluorescence microscopy after staining with Annexin V-FITC/PI or Annexin V-Cy3. Free radical formation induced by ultrasound was studied by ESR-spin trapping with DMPO as the spin trap. (Results and Discussion) Apoptosis increased with the incubation time after sonication. Early apoptosis observed at 6 hrs after sonication reached its maximum at 1 min-sonication and gradually decreased. On the other hand, secondary necrosis increased with sonication time. The effects of dissolved gases, Ar, N2, O2, air, N2O, and CO2, were investigated. Free radical formation was found in solutions saturated with Ar, N2, O2, and air, but not with N2O and CO2. Apoptosis induced by ultrasound was dependent on the dissolved gases in the order Ar=N2=O2=air ≫ N2O=CO2〜0. These results suggest that ultrasound-induced apoptosis was due to acoustic cavitation accompanying free radical formation. An echo contrast agent, Levovist at a concentration of 50 mg/ml for 6 hrs induced apoptosis but no apoptosis was observed with less than 20 mg/ml. When the cells were sonicated in the presence of Levovist, enhancement of secondary necrosis induced by ultrasound was observed at concentrations of more than 20 mg/ml. In contrast, no increase of apoptosis was observed in the combined treatments. These results suggest that Levovist at high concentration, acting as cavitation nuclei, enhances secondary necrosis induced by ultrasound due to increase of the membrane damage. (Conclusion) Evidence of apoptosis in U937 cells induced by 1 MHz ultrasound was obtained. Apoptosis induced by treatment with Levovist for 6 hrs was observed only at high concentration. In addition, Levovist enhanced secondary necrosis but not apoptosis induced by ultrasound.

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Water pollution by volatile chlorinated organic compounds, such as trichloroethylene, tetrachloroethylene, carbon tetrachloride, etc. has been becoming a serious problem in our society. In this study, these compounds were decomposed by high and low power ultrasonic irradiation with frequency of 28, 45, 100 and 200kHz. To achieve an effective decomposition rate with a low energy, we have investigated for the sonochemical decomposition in the presence of transition metal powders. In the heterogeneous aqueous solution, the pronounced cavitation effects were found to be observed under low power and low frequency ultrasonic irradiation. On the other hand, it was suggested that the reductive dechlorination of carbon tetrachloride occurred in the presence of transition metal powders and the rates were in the order of Zn > Fe > Cu. The rates of decomposition were accelerated by the addition of metal powders in all cases, however, the rates of decomposition of trichloroethylene and tetrachloroethylene were considerably slower than that of carbon tetrachloride.

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Colloids of metallic gold were prepared by ultrasonic irradiation of Na[AuCl_4] (Au(III)) with 1-propanol in aqueous solutions under various experimental conditions; i. e., the distances between reactor and oscillator, the temperature of solution and the output power. The rate of colloid formation was investigated with TEM and UV-vis specrtroscopic observation. The rate of reduction remarkably depended on the irradiation conditions. The maximum rate of Au(III) reduction was recognized at 20℃. The rate, furthermore, increased with increasing the output power of ultrasonic oscillator. The particle size of Au colloids obtained in the present sonochemical reduction was observed to be considerably small in comparison with conventional method with H_2 in gas phase. The average size of Au particle gradually increased with decreasing the rate of reduction, which controlled by the temperature of solution and by the distance between the reactor and oscillator.

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It is known that poly(N-sopropyl acrylamide) (PNIPA)/water solution shows phase separation over 31℃. In this study, We examined the ultrasonic polymerization of N-isopropyl acrylamide across this transition temperature. We found that i) in the case of 33℃, the weight average molecular weight (Mw) was higher around two times than that of 10℃, and that ii) the molecular weight distribution (Mw/Mn) almost did not change against sonication time at 33℃, while at 10℃, Mw/Mn decreased with sonication time. These results indicate that in the case of 33℃, polymer chain scission by ultrasound did not occur because the produced polymers aggregate in the solution.

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Polymerization utilizing ultrasonic has been widely studied. As the polymerization is progressed, physical and chemical properties of the solution are changed due to change of the concentration of polymer and monomer in the solution. Though this environmental change is considered to affect the creation of the sonication bubbles, generation of the radicals and diffusion properties of solutes, the effect has not been well understood. In this study, polyethylene glycol and polyethylene oxide which were chemically synthesized and are considered not to induce the ultrasound polymerization were used to control the environment of the solution. Radical concentration labeled by HTIO was measured by ESR during sonication in laboratory made cell. It was found that the radical generation is affected by chain ends when both of the ends are OH while it is not when either side of the chain is CH_3.

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Radicals generated by ultrasound have been applied polymerization. The ultrasound polymerization can be expected to have possibility to control structure of copolymers because generally the polymerization behavior is dependent on the monomer spiecies. However there have been few report on the copolymerization. We studied polymerization two of water- soluble monomers : N-isopropyl acrylamide and N-vinyl-2-pyrrolidon. We measured viscosity before and after the sonication. When initial viscosity of NIPAM and VP was around 2mPa・s, large viscosity increase accompanying the polymerization was observed.

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Analysis of multi-bubble sonoluminescence (MBSL) is difficult because of the interaction between bubbles. As a result, discussions of the experimental results are phenomenological. On the contrary, in the case of single-bubble sonoluminescence (SBSL) we can observe the luminescence light from only one bubble at stable conditions and the interaction from other bubbles are omitted. Analysis of SBSL phenomena gives useful information for understanding of the results obtained for MBSL in various kinds of solutions. In this work, hydrophobic effects on SBSL of water in the presence of aliphatic alcohols (methanol, ethanol, n-propanol, n-butanol and t-butanol) is studied and compared with those obtained for MBSL reported by Franz Grieser et al. In the presence of alcohol the sonoluminescence intensity decreased with increasing alcohol concentration. A good correlation was found to exist between the decline in the sonoluminescence intensity and the Gibbs surface excess of the alcohol at the air/water interface. Possible mechanisms responsible for the different behavior in the sonoluminescence intensity in the presence of the alcohols are discussed.

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Sonolytical inactivation of Cryptosporidium oosyst at frequencies of 28, 40, and 100kHz has been studied. At 28kHz oosysts had breaks in their wall and nuclei had leaked. More than 99.9% of oosysts were inactivated after 10 min sonication with 28kHz, however only 10% with 40kHz and no inactivation with 100kHz. Mice orally took the sonolized oosysts excreted no cryptosporidium oosysts even after two weeks.

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The decomposition of phthalic acid esters (PAEs), such as dimethyl phthalate (DMP), diethyl phthalate (DEP) and dibutyl phthalate (DBP) in water by ultrasonic irradiation is performed at an ultrasonic frequency of 200 kHz (intensity: 6 Wcm^<-2>). The decomposition of PAEs follows first-order kinetics and the rate of decomposition follows the order DEP > DBP > DMP. The rate of decomposition of DEP and rate of formation of hydrogen peroxide in pure water by ultrasonic irradiation depend upon the nature of dissolved gas. The reaction with hydroxyl radicals is found to be a preferential factor of the degradation of DEP in the pH 4 to 11 region. The rate of decomposition via hydrolysis increases with increasing pH in the pH over 11. The decomposition via thermal reaction did not appear to be affected by the change of pH. The rate for degradation of DEP in the presence of ultrasound is about 50 and 6 times higher than that in the absence of ultrasound (stirring) at pH 11, 12.5, respectively. From these results, the enhanced decomposition of DEP in the presence of ultrasound can be suggested and this may be due to effective temperature in the region between cavitation bubble and bulk solution.

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Iodination and bromination of simple alkanes or cycloalkanes using HCI_3 or CBr_4 with solid NaOH in neat alkanes under ultrasonic irradiation were studied. Reactions were faster with increased yields under ultrasound than silent reactions. 2- And 3-halogenated isomers were the major products with small amounts of 1-isomers. Isomer selectivity was similar for iodination and bromination. Mechanism of sonochemical acceleration will be discussed based on the proposed reaction mechanism involving radical intermediates.

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Chemical reactions under sonication are greatly affected by a geometrical placement of the constituents in sonochemical instrumentation since longitudinal ultrasonic waves travelling in liquid would cause reflection, interference and attenuation. Therefore, it is necessary to take account for the placement of the instrumental constituents. In order to establish a guideline for electrochemical application of ultrasounds, in the present work, an electrode reaction was examined under different placement of the electrode with ultrasounds produced by a various types of ultrasonic oscillator. In fact, the electrode reaction such as dimethyl maleate reduction was found to be affected by a placement of the working electrode in the system. For instance, the limiting current density for the reduction varied periodically along the axis of the ultrasonic beam, the distance between two maxima or two minima was almost constant, close to the theoretical half wave length in water when the immersible transducer was used as an ultrasonic device. On the other hand, when the stepped horn was used as an ultrasonic device, the limiting current density was decrease with an increase in the distance between the electrode surface and the top of the horn.

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