Formal Science / Chemistry Essay


Bromination of (E)-Stilbene

The bromination of (E)-Stilbene is an experiment to prove the hypothesis that the synthetization of meso-stilbene dibromide is highly conceivable. The hypothesis states that if the bromine-alkenes reaction is heated for roughly five minutes, at 120°C, the pyridium bromide perbromide with E-stilbene reaction would take place and meso-stilbene would be inadvertently produced. This reaction permits the reaction of the nucleophilic double bond which also comes in contact with the electrophilic bromine (Butz, 2017)

Bromine changes to electrophilic when induction occurs as a result of the capacity it holds to split up. According to Bruice (2014), “this induction occurs when there is a transmission of charge”. Bromine approaches (E)-stilbene’s double bond and splits up as it takes on a somewhat positive surge.

This reaction organizes and creates a cyclic bond with elements such as carbons, with both sp2, as well as sp3. This cyclic bond is, in turn, positively charged, and through a negative addition, the additional bromine, which has been negatively charged, then reacts with the rear of the cyclic compound and connects to either of the elements on the adjacent section of the bromine arrangement. Afterward, a 100% formed meso-stilbene with no stereoisomers is made.

Essentially, what this hypothesis posits is that "(E)-stilbene, in a solution of glacial acetic acid, reacted with pyridium bromide perbromide heated to 120°C and cooled in an ice bath, which would result in the formation of meso-stilbene. It was expected that only mesostilbene dibromide would be formed and that its formation could be tested by using IR.” (Butz, 2017)

This experiment aims to test an alternative reaction using (E)-stilbene, alkenes, and bromine reagent to produce pyridium bromide perbromide.

Note that most chemicals to be used in this test are toxic and should be used throughout the whole testing process inside an emission covering.


Below is the procedure in microscale as extracted from Butz, (2017);

• 230mg of (E)-stilbene was used instead of 600mg.

• 2.2ml of glacial acetic acid was used instead of 6ml.

• A 10ml round-bottom flask was used instead of a 50ml flask.

• The magnetic spin bar was a baby magnetic spin bar.

• 450mg of pyridium bromide perbromide was used instead of 1.2g.

• 2ml of glacial acetic acid was used to wash down the perbromide instead of 6ml.

• 4.5 ml of distilled water was used instead of 12ml.

• Acetone and distilled water were added drop-wise to the crystals instead of three 2ml of distilled water and two 2ml of acetone.


After this experiment had been conducted, it was discovered that the IR spectroscopy of the twin reactions has a relative similarity with the region of the fingerprint (Í‚ 500-1000cm-1).

The only divergence that could occur in this testing could come from the lack of the double carbon bond in the reaction of the meso-stilbene dibromide. As Butz (2017) notes in her essay, “the IR spectroscopy in the lab cannot measure the wavelength of carbonbromine bonds because it is not within the range of the machine.”

Brominating (E)-stilbene in an acetic acid solution produces mesostilbene crystals. Though the percentage was quite low. In support of this test is the ignition test. A share of the react exploded in green flakes, an indication of bromide.

As Butz (2017), hypothesises, this is as a result of “carbon-bromide bonds were not seen in the IR spectroscopy, the flame test was necessary to show that the (E)-stilbene had reacted with the pyridium bromide dibromide and created mesostilbene dibromide.”

One of the limitations of this experiment is improper temperatures which are most likely the main reasons for the occurrence of low percent yield. For the reaction to occur successfully, the heat must be about 120ºC.

After the bromination of (E)-Stillbene, the experimental data revealed that for the synthetization of the additional line of reactions to occur, meso-stilbene has to be achieved.

An addition to this discovery is that, without the right temperature, the percent yield of reaction will be very lowBromination of (E)-Stilbene, and will turn out to be an experimental failure. A sufficient amount of heat must be prepared for the reaction to be successfully synthesized.

The formation of meso-stilbene upon the successful reaction of the stilbene-alkene bromination and the mesostilbene dibromide is formed. These reactions could be tested using IR spectroscopy.

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