1501-58-2Relevant academic research and scientific papers
Accuracy of calculations of heats of reduction/hydrogenation: Application to some small ring systems
Wiberg, Kenneth B.
, p. 10393 - 10398 (2012)
The enthalpies of reduction of carbonyl compounds and hydrogenation of alkenes have been calculated at the HF, B3LYP, M06, MP2, G3, G4, CBS-QB3, CBS-APNO, and W1BD levels and, in the case of the first four methods, using a variety of basis sets up to aug-cc-pVTZ. The results are compared with the available experimental data, and it is found that the compound methods are generally more satisfactory than the others. Large basis sets are usually needed in order to reproduce experiments. Some C-C bond hydrogenolysis reactions also have been examined including those of bicycloalkanes and propellanes. In addition, the dimerization of the remarkably strained bicyclo[2.2.0]hex(1,4)ene was studied. The reaction forming a pentacyclic propellane was calculated to have ΔH = -57 kcal/mol, and the cleavage of the propellane to give a diene had ΔH = -71 kcal/mol. The strain energies of these compounds were estimated.
The Geometries of the s-Cis Conformers of Some Acyclic 1,3-Dienes: Planar or Twisted?
Squillacote, Michael E.,Semple, Thomas C.,Mui, Philip W.
, p. 6842 - 6846 (1985)
We have established a method to determine the geometry of the minor forms of acyclic 1,3-dienes.A high vacuum cryogenic trapping technique was used to obtain spectral data of these metastable conformers from mixtures equilibrated at 1100 K.This has enabled us to characterize the minor form of 2,3-dimethyl-1,3-butadiene (DMB) by IR and UV spectroscopy.Barriers to rotation of the metastable forms of isoprene and DMB to their stable s-trans forms have also been obtained.The UV spectra of acyclic 1,3-dienes are found to be determinant of structure and, on this basis, weassign a planar s-cis molecular framework to 1,3-butadiene and isoprene, and a gauche s-cis geometry to DMB.
Photochemistry of s-cis acyclic 1,3-dienes
Squillacote, Michael,Semple, Thomas C.
, p. 5546 - 5551 (1990)
We have examined the photochemistry of several s-cis acyclic 1,3-dienes and found that they close to cyclobutenes at 15 K. Extensive investigation of (E,E)-1,4-dideuterio-2,3-dimethyl-1,3-butadiene (DDMB) has shown that there are two pathways to thermal double bond isomerization: the first through an intermediate cyclobutene with a barrier of 48 kcal/mol and the second through an allylmethylene biradical with a barrier of 55 kcal/mol. Examination of the photochemistry of s-cis-DDMB shows for the first time that the s-cis conformer undergoes both electrocyclic closure and double bond isomerization. An excited-state surface is postulated that combines these two photochemical events and includes a concerted nonsynchronous disrotatory closure. This surface also allows prediction of the partitioning ratio between the two photochemical events.
The low-temperature photochemistry of s-cis acyclic 1,3-dienes
Squillacote, Michael,Semple, Thomas,Chen, JeWie,Liang, Fengting
, p. 634 - 639 (2007/10/03)
In this article we have examined the very low-temperature photochemistry of three acyclic 1,3-dienes. We have used high-temperature deposition techniques combined with matrix isolation to create samples enriched with the thermally meta-stable s-cis form. This technique has allowed us to examine the separate photochemistry of the s-cis and s-trans conformers. Our results suggest the presence and the absence of barriers on the excited-state surface. In particular, we have found that the electrocyclic closure and s-cis-s-trans photochemical isomerization stops at 15 K for 2,3-dimethyl-1,3-butadiene-d10. The closure occurs at higher temperatures in solution but is slowed by a deuterium isotope effect. The s-trans conformer of EE-2,4-hexadiene shows almost no photo-reactivity in a matrix under 254 nm irradiation, but the s-cis conformer is rapidly converted to ZE-2,4-hexadiene (ZE-HXD). The photoreactivity of ZE-HXD is similar in that there is a relatively quick conversion of the s-cis conformer under these conditions, with only a very slow conversion of the s-trans to photoproducts.
