Unimolecular gas-phase reactions of diethyl phthalate, isophthalate, and terephthalate upon electron ionization

Susumu Tajima, Masashi Mamada, Satoshi Nakajima, Yutaka Takahashi, Nico M.M. Nibbering

Research output: Contribution to journalArticle

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Abstract

Unimolecular gas-phase reactions of diethyl phthalate (1), isophthalate (2), and terephthalate (3), upon electron ionization, have been investigated by use of mass-analyzed ion kinetic energy (MIKE) spectrometry and deuterium labelling. The metastable molecular ions (1)+ decompose to give exclusively the ions m/z 176 ([M-CH3CH2OH]+) and not the ions by the loss of CH3CH2O as proposed earlier in the literature. The metastable molecular ions (2)+ and (3)+ fragment differently from (1)+ and lead not only to the formation of the major fragment ions m/z 194 ([M-CH2CH2]+) via a McLafferty rearrangement but also to minor fragment ions m/z 193 ([M-CH2CH3]+). Yet, molecular ions decomposing in the ion source all show as primary fragmentation channel the loss of CH3CH2O to give the ions at m/z 177, which further dissociate to give the ions at m/z 149 through the loss of C2H4 or CO, indicating the resulting ions are +COC6H4COOH and +C6H4COOCH2CH3. The +COC6H4COOH ions decompose into the m/z 121, 93, and 65 ions by the consecutive losses of three carbon monoxide molecules, respectively. Prior to the second CO loss, a migration of the OH group to the benzene ring occurs. During the metastable fragmentation of the +C6H4COOCH2CH3 ions no ethoxy migration occurs, in contrast to the methoxy migration taking place in the metastable decomposition of the lower homologue +C6H4COOCH3 ions.

Original languageEnglish
Pages (from-to)473-479
Number of pages7
JournalAustralian Journal of Chemistry
Volume56
Issue number5
DOIs
Publication statusPublished - Jul 8 2003

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Ionization
Gases
Ions
Electrons
Carbon Monoxide
terephthalic acid
isophthalate
diethyl phthalate
Deuterium
Ion sources
Benzene
Kinetic energy
Labeling
Spectrometry

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

Cite this

Unimolecular gas-phase reactions of diethyl phthalate, isophthalate, and terephthalate upon electron ionization. / Tajima, Susumu; Mamada, Masashi; Nakajima, Satoshi; Takahashi, Yutaka; Nibbering, Nico M.M.

In: Australian Journal of Chemistry, Vol. 56, No. 5, 08.07.2003, p. 473-479.

Research output: Contribution to journalArticle

Tajima, Susumu ; Mamada, Masashi ; Nakajima, Satoshi ; Takahashi, Yutaka ; Nibbering, Nico M.M. / Unimolecular gas-phase reactions of diethyl phthalate, isophthalate, and terephthalate upon electron ionization. In: Australian Journal of Chemistry. 2003 ; Vol. 56, No. 5. pp. 473-479.
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