Linked Life Data

11603963

Source:http://linkedlifedata.com/resource/pubmed/id/11603963

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
42
pubmed:dateCreated
2001-10-17
pubmed:abstractText
Rate constants and heats of reaction for the aromatization of benzene oxide (1) and the acid-catalyzed aromatization of benzene hydrate (2) in highly aqueous solution giving phenol and benzene, respectively, have been measured by heat-flow microcalorimetry. The measured heat of reaction of benzene oxide, DeltaH = -57.0 kcal mol(-1), is much larger than that of benzene hydrate, DeltaH = -38.7 kcal mol(-1), despite an unusually low reactivity of benzene oxide, rate ratio 0.08. The measured enthalpies agree with those calculated using the B3LYP hybrid functional corrected with solvation energies derived from semiempirical AM1/SM2 calculations. Comparison with the measured enthalpies of the corresponding reactions of the structurally related 1,3-cyclohexadiene oxide (3) and 2-cyclohexenol (4) of DeltaH = -24.9 kcal mol(-1) (includes a small calculated correction of -1.2 kcal mol(-1)) and DeltaH approximately 0 kcal mol(-1), respectively, gives a smaller aromatization energy for the benzene oxide than for the benzene hydrate reaction (DeltaDeltaDeltaH = 6.6 kcal mol(-1)). This suggests that benzene oxide is unusually stabilized by a significant amount of homoaromatization as has been proposed previously (J. Am. Chem. Soc. 1993, 115, 5458). This unusual stability accounts for more than half of the approximately 10(7) times lower than expected reactivity of benzene oxide toward acid-catalyzed isomerization. The rest is suggested to originate from an unusually high energy of the carbocation-forming transition state.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
24
pubmed:volume
123
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
10147-52
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2001
pubmed:articleTitle
Is benzene oxide homoaromatic? A microcalorimetric study.
pubmed:affiliation
Contribution from the Institute of Chemistry, University of Uppsala, Box 531, S-751 21 Uppsala, Sweden.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't