Apparent charge localization effects in the McLafferty rearrangement of acetate esters: Field ionization kinetic measurements

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AbstractThe relative rates of the McLafferty rearrangement in n‐butyl acetate and several related molecules have been examined over the time range 10−11 to 10−5 s by means of a field ionization mass spectrometric technique. It was found that the introduction of a substituent group of low ionization potential (phenyl, dimethylamino) at sites remote from the ester oxygens reduces the rate of the McLafferty rearrangement and that the rate becomes lower as the substituent is moved further away from the ester group. The results suggest that for the cases examined the charge on the molecular ion may be localized on the functional group of lowest ionization potential.