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Reference.org
Appel reaction
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<p>The Appel reaction is an <a href="/facts/Organic_reaction/SESmeGWm">organic reaction</a> that converts an <a href="/facts/Alcohol_(chemistry)/Y0SCTDkh">alcohol</a> into an <a href="/facts/Alkyl_chloride/IbblBkcB">alkyl chloride</a> using <a href="/facts/Triphenylphosphine/nYFNCVcJ">triphenylphosphine</a> and <a href="/facts/Carbon_tetrachloride/S2ekjT0E">carbon tetrachloride</a>. The use of <a href="/facts/Carbon_tetrabromide/sokAWGTC">carbon tetrabromide</a> or <a href="/facts/Bromine/oLfj3C7D">bromine</a> as a halide source will yield alkyl bromides, whereas using <a href="/facts/Carbon_tetraiodide/KzxaMSNA">carbon tetraiodide</a>, <a href="/facts/Methyl_iodide/uUKdue80">methyl iodide</a> or <a href="/facts/Iodine/JlfMecMf">iodine</a> gives <a href="/facts/Alkyl_iodide/P6LDC4IP">alkyl iodides</a>. The reaction is credited to and named after <a href="/facts/Rolf_Appel/P4cefnnI">Rolf Appel</a>, it had however been described earlier. The use of this reaction is becoming less common, due to <a href="/facts/Ccl4/S2ekjT0E">carbon tetrachloride</a> being restricted under the <a href="/facts/Montreal_protocol/Hmf70BQK">Montreal protocol</a>. </p> <p>Drawbacks to the reaction are the use of toxic halogenating agents and the coproduction of organophosphorus product that must be separated from the organic product. The phosphorus reagent can be used in <a href="/facts/Catalysis/LPBS7TQC">catalytic</a> quantities. The corresponding alkyl bromide can also be synthesised by addition of <a href="/facts/Lithium_bromide/YzaKEkwj">lithium bromide</a> as a source of bromide ions. A more sustainable version of the Appel reaction has been reported, which uses a catalytic amount of phosphine that is regenerated with <a href="/facts/Oxalyl_chloride/o2aR4J82">oxalyl chloride</a>. </p>