The origins of the base peak in the electron impact spectrum of limonene

✍ Scribed by Debi Harris; Stewart McKinnon; Robert K. Boyd

• Publisher: John Wiley and Sons
• Year: 1979
• Tongue: English
• Weight: 840 KB
• Volume: 14
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210140507

✦ Synopsis

The origins and nature of the [C&,]+* ions which form the base peak in the electron impact spectram of limonene, at nominal electron energies greater than 11 eV, have been investigated. Linked scan technigaes were used to study Onimolecnlar and collision induced fragmentation reactions. No fragmentation pathway leading to [C5&]+* could be fonnd. Measurement of ionization efeeiency curves indicated that the threshold for formation of [C,Eg]" lies above the range of internal energies deposited in incident ions by collisional activation. By a combination of comparisonS of collisionally activated spectra and energetic considerations, the [C,Eg]+* ions formed from limonene were shown to resemble those of the molecalar ion of isoprene, while the neotral fragment is most likely isoprene also. Dentenmu labelling experiments yielded evidence of extensive scrambling prior to fragmentation. The most probable mechanism of formation of [C5&]+' appears to involve a retro Diels-Alder reaction of a stroctarally intact molecalar ion of limonene.