Sonochemistry of Solutions

In this chapter, these reactions and their synthetic potential are discussed. Other descriptions, less aimed at s)mthesis but containing many useful elements, can be found in many books or reviews.  

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The sonochemistry of solutes dissolved in organic Hquids also remains largely unexplored. The sonochemistry of metal carbonyl compounds is an exception (57). Detailed studies of these systems led to important mechanistic understandings of the nature of sonochemistry. A variety of unusual reactivity patterns have been observed during ultrasonic irradiation, including multiple ligand dissociation, novel metal cluster formation, and the initiation of homogeneous catalysis at low ambient temperature (57). 

Hart Edwin J, Henglein A (1987) Sonochemistry of aqueous solutions H2-02 combustion in cavitation bubbles. J Phys Chem 91 3654—3656... 

By the proper choice of solvent and experimental conditions (i.e., low volatility, highly stable liquids at low temperature e.g., decane, -10° C), the rates of degradation of nonaqueous liquids can be made quite slow, well below those of water. This is of considerable advantage, since one may then observe the primary sonochemistry of dissolved substrates rather than secondary reactions with solvent fragments. In general, the examination of sonochemical reactions in aqueous solutions has produced results difficult to interpret due to the complexity of the secondary reactions which so readily occur. One may hope to see the increased use of low-volatility organic liquids in future sonochemical studies. 

In 1981, the first report on the sonochemistry of discrete organometallic complexes demonstrated the effect of ultrasound on iron carbonyls in alkane solutions (174). The transition metal carbonyls were chosen for these initial studies because their thermal and photochemical reactivities have been well characterized. The comparison among the thermal, photochemical, and sonochemical reactions of Fe(CO)5 provides an excellent example of the unique chemistry which homogeneous cavitation can... 

Riesz P, Kondo T, Carmichael AJ. Sonochemistry of acetone and acetonitrile in aqueous solutions. A spin-trapping study. Free Rad Res Comm 1993 19 S45-S53. 

Suslick has made an extensive study of the sonochemistry of Fe(CO)5 which he has used as a probe to explore the chemical effects of high intensity ultrasound. Suslick and Johnson [280] have also shown that sonication greatly facilitates the preparation of early transition metal carbonyl anions. Hence, sonication of vanadium trichloride and sodium sand in THF solution gave a 35 % yield of NaV(CO)g under 4.4 atmospheres of carbon monoxide at 10 °(i. The equivalent thermal reaction requires the reaction to be caried out at 160 °C under 200 atmospheres of carbon monoxide. That is, the temperatures and pressures produced by cavitation are comparable to the bomb conditions normally required for the preparation of these compounds [281]. Suslick s review [3] presents further evidence in support of this original observation however, no further details of this work have appeared to date. 

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