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Chen H, Cooks RG, Meurer EC, Eberlin MN: Hydrogen/Chlorine exchange reactions of gaseous carbanions. J Am Soc Mass Spectrom. 2005 Dec;16(12):2045-51. Epub 2005 Oct 24.
Gas-phase reactions of three typical carbanions CH (2) NO (2)(-), CH (2) CN (-), and CH (2) S (O) CH (3)(-) with the chloromethanes CH (2) Cl (2), CHCl (3), and CCl (4), examined by tandem mass spectrometry, show a novel hydrogen/chlorine exchange reaction. For example, reaction between the nitromethyl anion CH (2) NO (2)(-) and carbon tetrachloride CCl (4) forms the ion CHClNO (2)(-). The suggested reaction mechanism involves nucleophilic attack by CH (2) NO (2)(-) at the chlorine of CCl (4) followed by proton transfer within the resulting complex [CH (2) ClNO (2) + CCl (3)(-)] to form CHClNO (2)(-) and CHCl (3). Two other carbanions CH (2) CN (-) and CH (2) S (O) CH (3)(-) also undergo the novel hydrogen/chlorine exchange reactions with CCl (4) but to a much smaller extent, their higher nucleophilicities favoring competitive nucleophilic attack reactions. Proton abstraction is the exclusive pathway in the reactions of these carbanions with CHCl (3). While CH (2) CN (-) and CH (2) S (O) CH (3)(-) promote mainly proton abstraction and nucleophilic displacement in reactions with CH (2) Cl (2), CH (2) NO (2)(-) does not react. |
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