2016FallSymposiumURCreativityEngagement has ended
Tuesday, December 6 • 4:00pm - 4:40pm
A Computational Study of Substituent Effects on the Thioallylic Rearrangement Pathway'

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This goal of this study was to find the transition state structures and threshold energies of the thioallylic rearrangement mechanism, while observing the effects of different substituents. The initial structure is as follows: R-S-CH2CH=CR2, where the R groups represent different substituents. The substituents were chosen based upon electron donating (R= -NH2; -OCH3), electron withdrawing (R= -CF3), and steric properties (R= isopropyl; benzene) and were tested in a number of combinations on the three possible R positions. The transition state was found to be a short-lived sulfur bridge between the first and third carbon of the structure, resulting in the final state with the sulfur on the third carbon and a shift of the double bond to the first and second carbon (CH2=CHCR2-S-R). The specific energies found for the original thioallylic structure (R1=H; R4=CH3) were 48.0 kcal mol­-1 for the trans orientation and 48.4 kcal mol-1 for the cis orientation. Oxyallylic structures underwent the same calculations to compare the effect of oxygen versus sulfur in the rearrangement. Oxyallylic threshold energy values were 61.1 kcal mol-1 and 61.8 kcal mol-1 for the trans and cis isomers, respectively. The computational methods used in this study include Density Functional Theory (DFT) calculations to find transition state energies and mechanisms, as well as the Quantum Theory of Atoms in Molecules (QTAIM) as a model to visualize electron localization and densities in the described structures. Though this research was purely computational, the results are important to synthetic chemistry and biology. That said, there have been biological and biomedical studies that have found garlic derived organosulfur compounds to have capabilities to inhibit cell proliferation, and act in metabolic processes to aid in the treatment or management of certain diseases. Providing preliminary results on this system can be a beneficial starting point for the research and synthesis of compounds involving the thioallyl.


Tuesday December 6, 2016 4:00pm - 4:40pm
014 Zeis Hall