Diploma thesis deals with the stereoselectivity in Diels-Alder reaction between selected monosubstituated cyclopentadienes and monosubstituated ethenes from the quantum-chemical perspective. Spartan ’14 and semiempirical method PM3 was used to model the reactions. Fluorine, chlorine and methyl functional groups were used as substituents. For a given reaction between the diene and dienophile the folowing was determined: transition state structure, energy profile along the reaction coordinate, energy of activation, energies of reactants, product and of the reaction. These data were used to evaluate the stability of isomers.
In case of a reaction between 5-fluorocyclopenta-1,3-diene and ethene, the more energetically favourable (stable) product was the sin isomer. When changing the fluorine substituent for less electronegative chlorine, I’ve noticed a similar trend with smaller differences in activation energy. I assumed that the inductive effect with fluorine is a lot more present than with chlorine. In case of a reaction between cyclopenta-1,3-diene and fluoroethene, the difference in energies between the exo and endo products was negligible. Fluorine has much more influence as a substituent on diene. Finally, I made calculations for the reaction between 5-methylcylopenta-1,3-diene and fluoroethene, using one electron donating and one electron withdrawing substituent. I’ve noticed that in this reaction I would get the most anti/endo and anti/exo product.
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