Gas-phase reactions of three typical carbanions CH2NO 2-, CH2CN-, and CH 2S(O)CH3- with the chloromethanes CH 2Cl2, CHCl3, and CCl4, examined by tandem mass spectrometry, show a novel hydrogen/chlorine exchange reaction. For example, reaction between the nitromethyl anion CH2NO 2- and carbon tetrachloride CCl4 forms the ion CHClNO2-. The suggested reaction mechanism involves nucleophilic attack by CH2NO2- at the chlorine of CCl4 followed by proton transfer within the resulting complex [CH2ClNO2 + CCl3-] to form CHClNO2- and CHCl3. Two other carbanions CH2CN- and CH2S(O)CH3- also undergo the novel hydrogen/chlorine exchange reactions with CCl4 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 CHCl3. While CH2CN- and CH2S(O)CH3- promote mainly proton abstraction and nucleophilic displacement in reactions with CH2Cl2, CH2NO2- does not react.
|Number of pages
|Journal of the American Society for Mass Spectrometry
|Published - Dec 2005
All Science Journal Classification (ASJC) codes
- Structural Biology