Chemical ionization mass spectra of selected C3H6O compounds

✍ Scribed by Richard D. Bowen; Alex G. Harrison

• Book ID: 102964527
• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 912 KB
• Volume: 16
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210160404

✦ Synopsis

The chemical ionization mass spectra of five isomers of G&O (acetone, propionaldehyde, oxetane, propylene oxide and aUyl alcohol) have been determined using a variety of reagent gases (H2, D2, NJH,, C02/H2 and Corn2). The [CJ€,O]+ ions produced by protonation of these isomers undergo very similar reactions to those reported for analogous [C3H701+ metastable ions; however, decomposing ions generated by chemical ionization appear to have somewhat higher internal energies. The results of 'H labelling studies (D2 reagent gas or labelled analogues of C,&O) indicate that protonation occurs mainly on oxygen and are consistent with previous investigations of metastable oxonium ions. The protonated acetone ion is particularly stable, in agreement with the higher activation energies for fragmentation of this isomer than for other [C&H70]+ structnres. As the calculated heat of protonation of C&O is reduced by changing the reagent gas, so the extent to which fragmentation occurs decreases. This is discussed in the context of competition between fragmentation and collisional stabilization of the excited [Ca70]'* ion. It is concluded that on average a large fraction (approaching 1) of the exothermicity of the protonation reaction resides in the [C,H,O]+* ions produced initially.

Figure 1. Potential energy diagram for [&H,OI+ system.