MASS-SPECTRAL CHARACTERIZATION OF THE METHYL DERIVATIVE OF 3-CHLORO-4-(DICHLOROMETHYL)-5-HYDROXY-2(5H)-FURANONE (MX)

Previous interpretations of the electron impact mass spectrum of the methyl derivative 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) has suggested that the isotope cluster beginning at m/z 199 is due solely to the (M - OCH3) fragment ion. The relative abundance of the ratio among the ions at m/z 199, 201 and 203 deviates, however, from the theoretical ratio of ions in a three-chlorine isotope cluster. We hypothesized that the cluster arises from two distinct pathways and is composed of two fragment ions, each containing three chlorine atoms. Accordingly, we deconvoluted the original cluster at m/z 199 by assuming the presence of one three-chlorine isotope cluster at m/z 199 and another three-chlorine cluster at m/z 201. The result was that we obtained good agreement between the calculated and theoretical relative abundances of the ions. The presence of these two fragment ions was confirmed by high-resolution gas chromatography/high-resolution mass spectrometry at a resolving power of 20 000. The mass spectrum of MX, methylated with deuterated methanol, showed two fragment ions, one which arose from the loss of -OCD3 (m/z 199) and the other from the loss of -OCH (m/z 204). Tandem mass spectrometry of the m/z 229 [M - 1]+ fragment ion of the methyl derivative of MX showed a product ion at m/z 201. The fragment ion at m/z 201 is formed by the loss of -H from the molecular ion and the subsequent loss of -CO from the [M - 1]+ ion. The ion at m/z 199 originates from the molecular ion.