Torsional photoisomerization of substituted ethylenes: Application to stilbene

The trans to cis isomerization rate of stilbene is determined using a diffusional model for internal rotation. It is found that the rate is sensitive to the structural model for stilbene adopted and factors of 2 can be introduced by assuming the phenyl substituents are spherical. The preferred model...

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Veröffentlicht in:J. Chem. Phys.; (United States) 1981-04, Vol.74 (8), p.4627-4633
Hauptverfasser: Knauss, D. C., Evans, G. T.
Format: Artikel
Sprache:eng
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Zusammenfassung:The trans to cis isomerization rate of stilbene is determined using a diffusional model for internal rotation. It is found that the rate is sensitive to the structural model for stilbene adopted and factors of 2 can be introduced by assuming the phenyl substituents are spherical. The preferred model treats the phenyl substituents as collections of six spheres rigidly bound together and having a specific pitch angle with respect to the plane of the ethylene double bond. The use of a model potential function, chosen to agree qualitatively with experimental findings, allows the calculation of the isomerization rate as a function of the height of the barrier to rotation Q. The experimental value for the rate can be fit with this model using a barrier height ranging from 2–3 kcal/mole, in accord with previous estimates.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.441652