The elusive methene ylides CH2CIH, CH2FH and CH2OH2

Abstract The possible existence of the ylides CH 2 CIH, CH 25 FH and CH 2 OH 2 as stable neutral species in the gas phase has been investigated by the neutralization–reionization (NR) mass spectrometry of their radical cations using a double‐focusing mass spectrometer of reversed geometry. The experiments were, for the most part, performed under single‐collision conditions with Xe as the neutralization target gas and He and O 2 as reionization agents. For each ylidion a peak was observed in their NR mass spectrum which indicated that the neutral ylide had apparently been produced. However for CH 2 FH + ˙ and CH 2 OH 2 + ˙ the m / z 34 and m / z 32 peaks, respectively, were attribut‐able to interferences from the natural isotopic abundance of ions of lower mass. For CH 2 CIH + ˙, the NR recovery signal was found to arise from the presence of CH 3 CI + ˙ as an impurity in the ylidion flux. This was proved by examination of the collisional activation mass spectra of the [C, H 3 , CI] + ˙ ions produced in the NR mass spectra of the conventional ions and ylidions, an experiment performed using a triple‐sector mass spectrometer.