Photodissociation spectroscopic observation of some hydrocarbon ion rearrangements

• Published in: International journal of mass spectrometry and ion processes 1985-01, Vol.66 (3), p.313-326
• Main Authors: Dunbar, Robert C., Fitzgerald, George B., Hays, John D.
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics)
• ISSN: 0168-1176; 1873-2801
• DOI: 10.1016/0168-1176(85)80005-7

Photodissociation spectroscopy was used to characterize the non-fragmenting ion structures resulting from electron-impact ionization of several hydrocarbons in an ion cyclotron resonance ion trap. Structural conclusions were: the 1,4-pentadiene ion rearranges to the 1,3-pentadiene structure; the 1,4-octadiene ion rearranges to the 2,4-octadiene structure, and not to the 1,3-octadiene structure; the 1,4-cyclohexadiene ion rearranges to a conjugated structure, probably the 1,3-cyclohexadiene structure; methylcyclopentadiene and 1,3-cyclohexadiene yield an ion of the same structure, probably the 1,3-cyclohexadiene structure, although the methylcyclopentadiene structure cannot be ruled out; 1,3-cyclooctadiene and 1,4-cyclooctadiene yield the same ion, which may have the 1,3-cyclooctadiene structure, or may be a rearranged structure; 1,5-cyclooctadiene ion partially undergoes collision-induced rearrangement to this same ion structure. The generalization can be made that radical ions having two double bonds separated by a single carbon undergo facile rearrangement into conjugation.