Promotion of Organic Reactions by Ultrasound Coupling of Alkyl and Aryl Halides in the Presence of Lithium Metal and Ultrasound Timothy D. Lash' Department of Mathematics, Natural Sciences and Health Professions, Northern State College, Aberdeen. SD 57401 Donna Berry Department of Chemistry, University of Wisconsin, River Falls, WI 54022 Recent studies (1) of ultrasound to the . . of the auulication .. promotion of heterogeneous organic chemical reactions have shown promising rate enhancements. We have investigated the coupling of alkyl and aryl halides in the presence of lithium metal and ultrasound. The coupling . .of alkyl halides results in the formation of alkanes (Wurtz reaction) ( 2 ) .
Aryl halides couple to form biaryl compounds (Fittig reaction) (3).
Bondjouk and Han published a short note (4) on these reactions but gave few experimental details. AU of their products were purified by chromatography. We felt that these reactions could be conveniently modified, with more conventional work-up procedures, as undergraduate laboratory experiments. The Wurtz reaction is particularly difficult to carry out, and reported procedures (5) are not easily reproduced. Therefore. these exueriments illustrate the classical Wurtz and Fittig reactions, in addition to being a convenient application of oreanic sonochemistrv. ~romopropane,hromobutane, and brornopentane were found to react vigorouslv with lithium in ether solution when bombarded with-ultrasound to give hexane, octane, and decane, respectively, although little reaction took place in the absence of sonication.2 High boiling point contaminants codistilled with the products and IR and NMR spectra indicated that these were ethers; they were removed by washing the
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