Analysis of fluorene and 9,9-dialkylfluorenes by electrospray droplet impact (EDI)/SIMS

- Fluorene and 9, 9-dialkyl fluorenes were examined by EDI/SIMS.
- Information on molecular masses and side aliphatic chains could be obtained.
- Fragmentation paths of protonated fluorenes were examined by DFT calculations.
- Two alkyl substituents were eliminated through the concerted reactions to form C13H9+ upon the C(9a) protonation.

Fluorene and 9,9-dialkyl fluorenes were examined by electrospray droplet impact/secondary ion mass spectrometry (EDI/SIMS). From the major peaks: M+, [M+H]+, [M−R]+, and [M−R−(R−H)]+detected by EDI/SIMS, information on the molecular masses (M) and the side chains (R) could be obtainedfor dioctyl-, dihexyltri-, dioctyltri- and dihexylheptafluorenes. Despite the different alkyl substituents, dihexyltrifluorene (C75H98) and dioctyltrifluorene (C87H122) gave similar fragment-ion distribution patterns with the common peak values at m/z 339 and 517 in the two envelopes. This suggests that the fragmentation paths are similar for these two compounds. The ions with m/z 339 and 517 were tentatively assigned asC27H15+ and C41H25+in which all the alkyl substituents (R) were eliminated. Fragmentation paths of protonated fluorenes were examined by DFT calculations.The reaction paths of the elimination of side two alkyl chains to give fluorenyl cations as the final products were postulated for 9,9-dimethylfluorene and 9,9-dioctylfluorene.

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