E-Stilbene Lab Report

Two forms of stereochemistry can form product for the bromination of trans-cinnamic acid. Cis addition, also known as syn addition, is one way of forming product. This form of stereochemistry allows for the components of the reagent to add to the same side of the double bond. Trans, also known as anti addition, is the second form of addition that can create product for this experiment. Tran stereochemistry occurs when the components of the reagent add to opposite sides of the double bond. In this experiment, the formation of either erythro-2,3-dibromo-3-phenylpropanoic acid (trans/anti-R,S or S,R) or threo-2,3-dibromo-3-phenylpropanoic acid (cis/syn-R,R or S,S) was expected to occur.

In the formation of stilbene dibromide, there are three possible products. The first is meso-stilbene dibromide in which the bromines are on opposite sides of the former double bond. The other two products, d-stilbene dibromide and L-stilbene dibromide, are enantiomers with the two bromines on the same side of the former double bond. As enantiomers, d-stilbene dibromide and L-stilbene dibromide are non-superimposable mirror images of each other. Meso-stilbene dibromide makes up 90% of the yield of this reaction, while d-stilbene dibromide and L-stilbene dibromide make up only 10%.

The filter paper, holding the aspirin crystals, was removed from the funnel and was left to dry before being weighed. Once the aspirin crystals were weighed, the theoretical yield and the percent yield of the experiment were calculated. The procedure was repeated once more using the same steps.

The possible reasons for this discrepancy were discussed as the plausible mistakes committed in the procedure, such as allowing the solution to excessively cool, as well as the possibility of having used faulty or contaminated reagents and components. In general, in order to improve the results of future experiments, as well as to have potentially improved these results, a more diligent and strict manner of performing these experiments is necessary, as well as ensuring the purity and condition of any reagents used and to ensure that no objects such as glassware are compromised. Considering this information, the experiment must be considered a failure, although the purity of the small yield could be considered pure, the yield’s sheer lack of size is evidence of the fact that the reaction did not reach completion, whether it be because of a low temperature or a lack of purity in components. Therefore, it must be regretfully reported that the objective of the experiment was not

Possible reasoning for a lower yield could be loss of product during separation process, particularly leaving some product behind in Erlenmeyer flask. Another possible explanation could be the wash of product with not enough cold water, which increases the solubility of the product, thus lowering the yield. Also the product was lost during purification process, recrystallization. Solid could be dissolved below the boiling point of the solution, thus required more solvent, resulting in a lower

1. Suggest at least one chemical reason why your percent yield is less than 100%. (Incomplete reactions? Side reactions? Stability of reagents?)

7. Plan: Each student in a group of three will work to purify the product of the reaction with cis-stilbene, trans-stilbene, or styrene. The crude products will be purified through recrystallization. This purification process will be performed several times. When the recrystallization is complete, a vacuum filtration will be executed to filter out the crystals. An NMR spectrum will be taken of the recrystallized product.

What was concluded when doing the lab was to determine which product of the equation was the limiting reactant. When doing all the calculations were 83.1% of the yield of the compound. It is very close to having almost the perfect percentage of the limiting yield when doing the

In order to calculate the percent yield, we first had to determine the moles of the limiting reactant, which was anthranilic acid in this case, by dividing the mass of was anthranilic acid we weighted in the beginning of the lab (2.001g) and dividing it with the molar mass of was anthranilic acid. Thus obtaining the value of 0.01456g. Then in order to calculate the theoretical yield, we multiplied the moles of was anthranilic acid with the molar mass of N-acetylanthranilic acid and the mole ration which was 1:1, thus obtaining the value of 2.614g. Finally, to determine the percent yield, we divided the mass of the pure crystals with the theoretical yield and multiplied it by a 100, thus obtaining a 16% yield. Discussion and Conclusion The reaction of anthranilic acid lead to the end product of

At this point the flask was attached to a refluxing apparatus. This process of refluxing helps to purify the mixture and keep the reaction at a constant temperature. Also, before the reaction mixture began to boil the separation of a clear top layer and a cloudy bottom layer helped to indicate that the reaction was working properly. The top layer was the alkyl bromide since the other components of the aqueous layer have the greater density. After the 45 minute refluxing process was complete, the apparatus was set up for simple distillation apparatus distillation commenced. Distillation took place until no more drops of product were dripping from the distillation head. The first drop of distillate occurred when the thermometer read 75°C, the actual temperature was probably a bit higher since the vapors might not have fully reached the bulb of the thermometer. The final drop of distillate was collected at about 115°C. Once the distillate was collected, it was placed in a seperatory funnel and the reaction flask was rinsed with 10 mL of water and added to the seperatory funnel. Rinsing the funnel ensured that all of the distillate from the distillation process was removed from the reaction flask and no product was left on the walls of the flask. After the water was added, two layers formed in the funnel. The top layer was the water and the bottom layer was the 1-bromobutane since the density of 1-bromobutane is higher than that of water.

This low yield could also be the result of the experiment not being performed optimally resulting in the reaction not completing fully which was is not supported by the observation of the decolorization of solution. The melting point of the Stilbene dibromide product was 211 - 220 °C. Because of the broad melting point range (larger than 5 °C) the product is impure. These impurities are likely a result of the improperly collecting the product during vacuum filtration. Either the compound was not filtered correctly or the filter paper flaked off during collection.

The total percent yield for this experiment was 6.98 %( figure 1). The yield for the ortho isomer was 4.75 %, and 2.23 % for the para isomer. The total percent yield was very low because some errors may have been coming from isolation of product. Also, it could have been from the column chromatography when we took each fractions of the

The purpose of this experiment was to synthesize 2-methyl-1-butene and 2-methyl-2-butene. We later confirmed the alkenes in each product with Baeyer and Bromine test. Through Gas liquid chromatography we could calculate the yield percentage. E1 and E2 are similar yet, different reactions. In the E1 reaction, the rate determining step is the loss of the leaving group when the mixed with a solvent and an energy source is provided, in this case it was heat.

Part 2 to determine the empirical formula and percentage yield of the compound synthesized in Part 1. Spectrophotometry is a routine laboratory test that has the added advantage

That the more stable alkene trans-2-butene, is the major product at approximately 82%. While, the two minor products would be 1-butene at 14%, and cis-2-butene at only approximately 4%.