Mécanique moleculaire: étude des stabilités relatives et des conformations des dimères de l'isophorone

Robinet, Germaine; Barthelat, M.; Rivière, M.; Devillers, Jean

doi:10.1016/0166-1280(92)87129-n

Cited by 2 publications

(5 citation statements)

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“…We observed very different values in the steric energy in comparison with those reported for truxinate esters and these values were higher than those previously reported for the cinnamate dimers. 22 In particular the bending energy was the main cause of this difference. This effect is probably due to the presence of the more polar furan ring in the molecule.…”

Section: Figurementioning

confidence: 99%

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The photochemical dimerization of 3-heteroaryl-acrylates

D’Auria¹,

Emanuele²,

Esposito³

et al. 2002

Arkivoc

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A detailed explanation of the observed photochemical reactivity of 3-heteroaryl-acrylates is furnished on the basis of a comprehensive review of the photochemical dimerizations of this type of compounds. The reactions occurred in the triplet state of the reagents showing good regio-and stereoselectivities. The regioselectivity can be explained assuming that the dimerization reaction is frontier orbitals controlled. The reaction of the triplet state of a reagent with another molecule of the reagent leads to the formation of the most stable biradical. This behavior induces a control in the relative stereochemistry of the two ester functions. The following cyclization occurs in order to obtain the products under kinetic control. This cyclization allows the formation of the most stable isomers.

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Section: Figurementioning

confidence: 99%

“…22 In our case, we performed molecular mechanics calculations by using MM+ program in HyperChem packet. In this case we observed a completely different trend.…”

Section: Figurementioning

confidence: 99%

The photochemical dimerization of 3-heteroaryl-acrylates

D’Auria¹,

Emanuele²,

Esposito³

et al. 2002

Arkivoc

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“…I. Topochemical Control of Photodimerization. In an earlier molecular mechanics study, , we compared the relative stabilities and conformations of isophorone photodimers. The highest energies were observed for the HH photodimers.…”

Section: Discussionmentioning

confidence: 99%

“…This theoretical prediction based on the stability of photodimers is clearly contradicted by the experimental results summarized above. This suggests that, irrespective of the reaction medium, the photodimerization is not controlled by the stability of photoproducts but must be kinetically controlled …”

Section: Discussionmentioning

confidence: 99%

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Supramolecularity and Photodimerization of Isophorone: FTIR and Molecular Mechanics Studies

et al. 1998

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The FTIR spectroscopic study of isophorone solvation in various media using the CdO group as the microenvironmental probe shows that in aprotic medium (cyclohexane) at least two forms are present, even at low concentrations: the monomolecular form and the aggregated forms (dimers and larger). In hydroxylated organic media (butanol), only monosolvated forms are present. In aqueous solutions, solvated species with various degrees of aggregation and hydration can be identified. Molecular mechanics studies show that isophorone, which is an R-enone, has a preference for an aggregated form over the monomolecular form. Further, the hydrogen atoms of a water molecule can take part in a stabilizing interaction with the carbonyl oxygen atoms of two isophorone molecules. The information on the solvation states (derived from FTIR spectroscopy) and on the nature of the supramolecular structures (calculated via molecular mechanics) have been correlated to the results of photodimerization. Finally, we propose a mechanism of photoreaction, based on the supramolecular structures which are flexible and therefore have a modifiable molecular structure and whose geometry is determined by the interactions with the medium. Experimental SectionReagents. The solvents for spectroscopy, cyclohexane, n-butanol, and methanol (Merck, spectroscopically pure), D 2 O 99.8% (Spin et Techniques), were used as supplied. The water was distilled or double distilled. Isophorone, 1 (Aldrich), was distilled to purity as checked by gas chromatography (GC) and by 1 H NMR. Deuterated isophorone, 2, 12 was prepared by isotope exchange using the method described in ref 15.Photodimerization. The concentration of 1 in the reaction mixture was varied from 0.02 to 0.06 M in water; it was constant at 0.1 M in the other media. The reaction mix (after bubbling with nitrogen or argon for 30 min) was irradiated for 24 h (ambient temperature 25-30 °C) in quartz tubes in a RPR 100 † In memory of my mother.

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Mécanique moleculaire: étude des stabilités relatives et des conformations des dimères de l'isophorone

Cited by 2 publications

References 7 publications

The photochemical dimerization of 3-heteroaryl-acrylates

The photochemical dimerization of 3-heteroaryl-acrylates

Supramolecularity and Photodimerization of Isophorone: FTIR and Molecular Mechanics Studies

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