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Bromination Of E-Stilbene Lab Report

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In this experiment, the bromination of E-Stilbene, or trans 1, 2 diphenylethene was performed in order to figure out whether the cation intermediate in the mechanism was cyclic or acyclic. The hypothesis was that if the product of the reaction was 100% meso- 1,2-dibromo-1,2-diphenylethane, or meso-stilbene dibromide, the intermediate was cyclic, but if there was a 50:25:25 ration of meso, D, and L isomers, the intermediate was acyclic. In the mechanism with the cyclic intermediate, the pi electrons in the E-Stilbene double bond attack the bromine molecule, causing heterolytic cleavage, resulting in the formation of a bromide ion, and a cyclic structure on the E-Stilbene where a bromine atom forms partial bonds with both the carbons involved in the double bond. This cyclic structure provides steric hindrance on one side of the E-Stilbene molecule. The bromide ion then attacks one of the carbons in the double bond, forming a bond with that carbon, and causing the other bromine atom to form a bond with the opposite carbon, resulting in the …show more content…

However, due to the hindrance from the cyclic structure, the bromide ion is only able to attack from the side opposite that of the cyclic structure. Since the cyclic structure can form on either side of the double

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IR confirmed some impurities were present as peaks were still present in the C=C double bond area around 1600 cm-1 to 1680 cm-1. Peak at 625.81 cm-1 is indicative of a C-Br bond showing the bromination was successful. Based on 1.4598 grams of recrystallized stilbene dibromide the theoretical yield of the target 1,2-diphenylacetylene was found to be 1.0754 grams. With 0.9221 grams recovered the % yield was an acceptable 85.7%. Impurities after bromination may have been due to some HBr not forming into Br2 or due to the presence of remaining water.

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=O, at 1719 cm-1 which identifies that 4 still has the ketone group produced in the oxidation of the secondary alcohol in the second step. There is not a peak at 550 cm -1 which shows that the elimination of the bromine atom has taken

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According to Chemspider website, 4-bromoacetanilide has a melting point of 165°C – 169°C (1) and 2-bromoacetanilide has a melting point of 96.5°C – 100.5°C (2). The melting point range of the experimental mass was 166.1°C – 168.1°C. This melting point was in the range of the literature value which confirmed that 4-bromoacetanilide was only produced and it was pure. From the bromination of aniline, only 0.203g (88.3%) of 2,4,6-tribromoaniline was collected at the end.

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This is done quickly do to the fact that it the proton antiperiplanar to the leaving group which is the bromide. The bond between the proton and the carbon shifted between the two carbons to form a double bond. Bromine became the leaving group so that the alkene could be formed which is known as (E)-1-Bromo-1,2-diphenylethylene. Another elimination reaction occurred with the product still being in the KOH. This reaction is done

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Bromine is a very good electrophile so upon adding the protons to the solution, the lone pairs of electrons make a partial bond which causes there to be a shift in the direction of the electron density. Therefore, this creates a partially positive bromine atom that increases its

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In free-radical chain reactions, a diatomic halogen molecule is reacted with the most reactive hydrogen atom on a carbon chain to form a halide and a haloalkane. In the case of bromination, diatomic bromine is reacted with a carbon chain to form hydrobromic acid and an alkyl halide. The first step in the reaction is initiation, or the formation of bromine radicals. These radicals can then react with hydrogens along the carbon chain through propagation to form hydrobromic acid and a carbon radical. Additionally, the carbon radicals can react with other bromine radicals to form carbon-bromine bonds.

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Through the use of a 5 mL conical vial, a spin vane, and a water-cooled condenser, a mixture of 0.5 mL of 1-hexene, 2 mL of 48% aqueous HBr, and 150 mg of tetrabutylammonium bromide is put under heat for 2 hours to reflux. The use of heat under reflux, in this case, is diverse from the tradition application of heat, due to the use of a water-cooled condenser under heat in order to prevent the escape of reagents, due to the fact that the organic reaction is very slow and takes a long time to display differences in effects, as well as the fact that though application of heat to the mixture may increase the rate of reaction, some organic compounds may also vaporize and disturb the proceeds of the reaction, due to the high heat and low boiling points of the compounds. Furthermore, a vigorous stir of the mixture under heat at this point is very important, for it enables and ensures the liquefying of all solids with the solvent. The reaction mixture is then put to cool to room temperature, which completes the initial reaction setup and reflux conditions. A HBr addition to 1-hexene and its product is shown

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This polarization causes a partial positive charge on one bromine (electrophile) and a partial negative charge on the other bromine. The pi bond of the carbons break and a sigma bond of carbon and bromine is made. Instead of a carbocation, the other carbon also forms a nonbonding electron pair with the bromine. This cyclic bromonium ion stabilizes the positive charge and there is no need of a carbocation formation. Then the other bromide ion acts as the nucleophile and attacks the other carbon which bears the partial positive charge and breaks the cyclic interaction.

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