Sonolysis of Fe

The proposed chemical mechanism by which Fe3(C0)i2 is formed during the sonolysis of Fe(C0)5 is shown in Equations 1-4. 

Suslick et al. [20] later demonstrated the link between the intensity of caviation in an organic liquid and its vapour pressure. Sonolysis of Fe(CO)s... 

It was also discovered that sonolysis of slurries of diiron nonacarbonyl and vinyl epoxide in benzene solution gives good yields of the required product [261]. However, Suslick reports that the only products generated by sonolysis of Fe2(CO)9 are Fe(CO)5 and finely divided iron [262]. Sonolysis of Fe(CO)j itself leads to formation of the dark green Fe3(CO)j2. In considering the mechanism of this reaction Suslick concluded that the initial step was formation of a tri-carbonyliron intermediate. Subsequent reaction with Fe(CO)5 could then be invoked to explain the presence of Fc3(CO) 2 (Figure 23). 

FIGURE 8 Sonoluminescence of excited state Fe atoms produced during sonolysis of Fe(CO)s dissolved in silicone oil under Ar compared to the calculated spectrum. The emission temperature observed from MBSL from excited state Fe, Cr, and Mo atoms is 4900 250 K. [From Suslick, K. S. et al. (1999). Phil. Trans. Roy. Soc. London A, 357, 342. With permission.]... 

Exposing an aqueous solution of Fe(ll) to ultrasonication results in its oxidation (Eq for the Fe(ll)/Fe(lll) couple is -0.771 V). Under these conditions, Fe(ll) interacts with the OH radicals generated by water sonolysis to form Fe(lll) and OH, according to ... 

A second spectroscopic thermometer comes from the relative intensities of atomic emission lines in the sonoluminescence spectra of excited-state metal atoms produced by sonolysis of volatile Fe, Cr, and Mo carbonyls. Sufficient spectral information about emissivities of many metal atom excited states are available to readily calculate emission spectra as a function of temperature. Because of this, the emission spectra of metal atoms are extensively used by astronomers to monitor the surface temperature of stars. From comparison of calculated spectra and the observed MBSL spectra from metal carbonyls, another measurement of the cavitation temperature was obtained.6 The effective emission temperature from metal atom emission during cavitation under argon at 20 kHz is 4,900 250 K. 

In a non-aqueous medium, radicals other than OH can be generated. The sonolysis of organic solvents was thus studied by e.s.r. (p. 59). The decomposition of DPPH (2,2-diphenyl-l-picryl-hydrazyl) is a very sensitive probe of sonolysis of organic species, was used to determine a relative scale of the intensity of cavitation (p. 56). The decomposition of iron pentacarbonyl Fe(CO)5 cannot be used due to the toxicity of this molecule. The common drawback associated with chemical dosimeters is the dependence on frequency. Such standards should be considered as relative methods unable to provide an absolute value of energy. 

The sonochemical method has been applied to obtain nanoparticles of magnets such as Fe, Fc304, Fc203, cobalt ferrite and copper ferrite in Refs [259, 260, 267]. If the sonication occurs in the presence of oxygen, the oxide phases are obtained [267, 268]. In the case of Fc203, the sonolysis results in amorphous nanopowder,... 

In the analogous reaction of P-ionone with FejCCO), 1 h of sonolysis gave a 4 1 mixture of endo and exo complexes (Scheme 134). In contrast, Cais and Maoz report that the thermal reaction of the diene with Fe(CO)j leads to isolation of a 3 1 ratio of products in favour of the exo-isomer [278]. However, it should also be noted that the overall yield of the thermal reaction was only 21 %, that is a factor of three less than that obtained under sonolytic conditions. 

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