Formation of CH3CH2OCH3 and ˙CH2 +OHCH2CH3 from ionized 2‐ethoxyethanol and theoretical and experimental studies of the reactions of ˙CH2 +OHCH2CH3

David J. McAdoo, Charles E. Hudson, V-M Ramanujam, M. George

Research output: Contribution to journalArticle

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Abstract

It is concluded that C3H8O formed by dissociation of ionized 2‐ethoxyethanol (8) is a mixture of CH3CH2OCH3 (7) and ˙CH2 +OHCH2CH3 (2). Formation of 7 and CH3CH2 +OHCH3 (12) is attributed to dissociations of species formed by the hydrogen transfers [CH3CH2OCH2 + ˙CH2OH] → [CH3CH2OCH2OCH3 CH2O] → [CH3CH2 +OHCH3HCO˙]. Production of 7 competes weakly with dissociation to CH3CH2 +OCH2 (13) and to 12. The low abundance of 7 is attributed to the simple dissociation 8 → 13 being both energetically and entropically favored, and a second H‐transfer to give 12 being energetically favored. The threshold for forming 7 is 45 kJ mol−1 above that for dissociation directly to 13, so formation of 7 is the first ion‐neutral complex‐mediated elimination found to have a threshold above that for the competing simple dissociation. The low abundance of 7 also demonstrates that ion–neutral complexes can be intermediates without obviously revealing their presence by direct dissociation. Experimental results suggest that 2 isomerizes to CH3CH2CH2OH (5) and then dissociates by eliminating water. Ab initio results support the feasibility of 2 → CH3 +OHCH2CH2 ˙ (1) and 2 → 5. However, experimental observations suggest that 2 → 1 does not occur. This is attributed to strong competition from dissociation and isomerization to 5. The transition state for 2 → 5 resembles [CH3CH2CH2OH], and a cyclic transition state for 2 → 5 is ruled out. When the ethyl‐oxygen bond in 2 is simply lengthened, the charge is initially concentrated on ethyl, but it switches to CH2OH in a curve crossing at an apparent transition state for CO bond breaking.

Original languageEnglish (US)
Pages (from-to)1210-1217
Number of pages8
JournalOrganic Mass Spectrometry
Volume28
Issue number10
DOIs
StatePublished - 1993
Externally publishedYes

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Carbon Monoxide
Hydrogen
Theoretical Models
dissociation
Water
thresholds
Isomerization
isomerization
elimination
switches
Switches
curves
hydrogen
water

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Medicine
  • Instrumentation

Cite this

Formation of CH3CH2OCH3 and ˙CH2 +OHCH2CH3 from ionized 2‐ethoxyethanol and theoretical and experimental studies of the reactions of ˙CH2 +OHCH2CH3 . / McAdoo, David J.; Hudson, Charles E.; Ramanujam, V-M; George, M.

In: Organic Mass Spectrometry, Vol. 28, No. 10, 1993, p. 1210-1217.

Research output: Contribution to journalArticle

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abstract = "It is concluded that C3H8O+˙ formed by dissociation of ionized 2‐ethoxyethanol (8) is a mixture of CH3CH2OCH3 +˙ (7) and ˙CH2 +OHCH2CH3 (2). Formation of 7 and CH3CH2 +OHCH3 (12) is attributed to dissociations of species formed by the hydrogen transfers [CH3CH2OCH2 + ˙CH2OH] → [CH3CH2OCH2OCH3 +˙ CH2O] → [CH3CH2 +OHCH3HCO˙]. Production of 7 competes weakly with dissociation to CH3CH2 +OCH2 (13) and to 12. The low abundance of 7 is attributed to the simple dissociation 8 → 13 being both energetically and entropically favored, and a second H‐transfer to give 12 being energetically favored. The threshold for forming 7 is 45 kJ mol−1 above that for dissociation directly to 13, so formation of 7 is the first ion‐neutral complex‐mediated elimination found to have a threshold above that for the competing simple dissociation. The low abundance of 7 also demonstrates that ion–neutral complexes can be intermediates without obviously revealing their presence by direct dissociation. Experimental results suggest that 2 isomerizes to CH3CH2CH2OH+˙ (5) and then dissociates by eliminating water. Ab initio results support the feasibility of 2 → CH3 +OHCH2CH2 ˙ (1) and 2 → 5. However, experimental observations suggest that 2 → 1 does not occur. This is attributed to strong competition from dissociation and isomerization to 5. The transition state for 2 → 5 resembles [CH3CH2CH2OH]+˙, and a cyclic transition state for 2 → 5 is ruled out. When the ethyl‐oxygen bond in 2 is simply lengthened, the charge is initially concentrated on ethyl, but it switches to CH2OH in a curve crossing at an apparent transition state for CO bond breaking.",
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AB - It is concluded that C3H8O+˙ formed by dissociation of ionized 2‐ethoxyethanol (8) is a mixture of CH3CH2OCH3 +˙ (7) and ˙CH2 +OHCH2CH3 (2). Formation of 7 and CH3CH2 +OHCH3 (12) is attributed to dissociations of species formed by the hydrogen transfers [CH3CH2OCH2 + ˙CH2OH] → [CH3CH2OCH2OCH3 +˙ CH2O] → [CH3CH2 +OHCH3HCO˙]. Production of 7 competes weakly with dissociation to CH3CH2 +OCH2 (13) and to 12. The low abundance of 7 is attributed to the simple dissociation 8 → 13 being both energetically and entropically favored, and a second H‐transfer to give 12 being energetically favored. The threshold for forming 7 is 45 kJ mol−1 above that for dissociation directly to 13, so formation of 7 is the first ion‐neutral complex‐mediated elimination found to have a threshold above that for the competing simple dissociation. The low abundance of 7 also demonstrates that ion–neutral complexes can be intermediates without obviously revealing their presence by direct dissociation. Experimental results suggest that 2 isomerizes to CH3CH2CH2OH+˙ (5) and then dissociates by eliminating water. Ab initio results support the feasibility of 2 → CH3 +OHCH2CH2 ˙ (1) and 2 → 5. However, experimental observations suggest that 2 → 1 does not occur. This is attributed to strong competition from dissociation and isomerization to 5. The transition state for 2 → 5 resembles [CH3CH2CH2OH]+˙, and a cyclic transition state for 2 → 5 is ruled out. When the ethyl‐oxygen bond in 2 is simply lengthened, the charge is initially concentrated on ethyl, but it switches to CH2OH in a curve crossing at an apparent transition state for CO bond breaking.

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