To Determine the Mechanism of the Reaction of Trans-Cinnamic Acid with the Addition of Bromines Essay Example

be less favorable, but according to research done on a similar experiment by Heasley, Bower, Dougharty, and Easdon, the syn attachment of the bromine molecules was not prevented

Another important finding of their research was that higher concentrations of halogens increased the percentage of syn product . Another factor that is important is the polarity of the solvent. According to research done by Douglas Naae, polarity of the solvent has many effects on the stereochemistry as well. The antistereospecificity decreases the amount of bridging done by bromine as the solvent’s polarity starts to rise. The substituents on the  -carbon also play a huge role. According to Naae, a factor that drives a reaction to perform syn addition is if the substituents is a good leaving group. If the intermediate has enough time to rotate or to form a bridged ion, the favorability of syn addition decreases

It makes sense then that another factor that helps syn addition is if the concentration of the substituents is high and also when the halogen concentration is high. In an experiment by Antonius A. M. Roof, William J. Winter, and Paul D. Bartlett, they studied the kinetics of the reaction and found that syn isomer ends with serious compression issues on its bridge. They concluded that if any mechanism had a late transition state then syn the syn isomer would occur because there would be an easy access path to the carbon.

There are several ways that the reaction can go syn or anti, but syn addition will only occur if aided. Anti addition occurs when the carbon-carbon bond undergoes rotation and syn addition occurs when the intermediate collapses providing the means

for a carbocation to form. Methodology The general Procedure found in Lehman was used for this experiment. A variance in the procedure is that an NMR will also be used to analyze the results. The PCSpartanPlus molecular modeling system was used on Tuesday, January 17th, to calculate the frequency and the equilibrium geometry.

Conclusion

• For the syn addition of the bromines the mechanism would be the following
• For the anti addition of the bromines the mechanism would be the following

The final product was be erythro-2,3-dibromo-3-phenylpropanoic. It went through syn addition as shown by the mechanism because the molecule is more stable with the carbocation next to the benzene ring than it is with the bromine triangle. The data is backed up by the J values corresponding to the angles at 167 which was the erythro-2,3-dibromo-3-phenylpropanoic as well as with the melting point data which was only a few degrees off of the literature value for erythro-2,3-dibromo-3-phenylpropanoic and around a hundred degrees off of the alternate.