Open AccessUnimolecular photochemistry of n-alkenes studied by photodissociation-photoionization mass spectrometry
Author(s) -
Scott E. Van Bramer,
Philip L. Ross,
Murray V. Johnston
Publication year - 1993
Publication title -
journal of the american society for mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.961
H-Index - 127
eISSN - 1879-1123
pISSN - 1044-0305
DOI - 10.1016/1044-0305(93)85044-x
Subject(s) - chemistry , photoionization , photodissociation , mass spectrometry , photochemistry , analytical chemistry (journal) , chromatography , ionization , organic chemistry , ion
The 193-nm unimolecular photochemistry of n-alkenes from C5 to C14 is studied by photodissociation-photoionization mass spectrometry (PDPI/MS). In PDPI/MS, a UV laser induces neutral unimolecular photodissociation. The resulting neutral fragments and any remaining parent molecules are then softly ionized with coherent vacuum UV radiation and mass analyzed. Photodissociation of n-alkenes is dominated by cleavage of the β C-C bond. Products of α- and γ-cleavage are typically less than 20% as abundant as the β-cleavage fragments. Secondary fragmentation of the primary products occurs both by neutral fragmentation during photodissociation and by ionic fragmentation during photoionization. The energetics of the neutral secondary reactions indicate that between 400 and 500 kJ/mol is consumed during photodissociation. The abundances of many secondary fragmentation products decrease with increasing molecular size. Because neutral fragmentation occurs without significant isomerization, PDPI/MS provides structural information that is not available from ionic fragmentation in conventional mass spectrometric experiments.