The mass spectra of organic compounds. 7th Communication. 4,4-Dimethyl-1-pentene

✍ Scribed by José Carlos Antunes Marques; Arnold Falick; Andréas Heusler; Daniel Stahl; Pierre Tecon; Tino Gäumann

• Book ID: 102859433
• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: German
• Weight: 505 KB
• Volume: 67
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19840670211

✦ Synopsis

from the molecular ions of a number of ',C-labeled analogs of 4,4-dimethyl-l-pentene was studied both in normal (source) 70-eV electron impact (El) spectra and in metastable spectra. For loss of CH, in the source, 96% of the methyl comes from positions 5, 5' and 5", while the remainder comes from position 1. In the metastable spectra, loss of C-1 (16%) and C-3 (9%) is increasing in importance. The loss of ethylene is a particular case: either C-1 or C-3 are lost with any other C-atom from positions 2,5,5', and 5" (8 x 11 %) in the metastable spectra, the probability for simultaneous loss of C-1 and C-3 being 6%. If C-1 seems to have a somewhat higher probability than C-3 for fragmentation within the source, these two positions become completely equivalent in the metastable time range. The T-values (kinetic energy release) for the different positions show small, but statistically different values and a small isotope effect. Loss of C,H, (allylic cleavage) is 100% C-1, C-2 and C-3, i.e., no evidence for skeletal rearrangement is seen. This is also true for loss of C,H, (McLufferty rearrangement) within the source, but in metastable decay the other positions gain in importance. The neutral fragment C,H, appears to be the result of consecutive loss of CH, and C,H,, rather than a one-step loss of propyl radical or the inverse reactions sequence. No metastable reaction can be seen for this reaction. Decomposition of labeled C,H:, and C,H; secondary ions occurs in an essentially random fashion.

') 6th Communication, see [l]