ISSN:
0030-493X
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
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.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/oms.1210281036
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