Bromination of trans Stilbene using pyridinium lab report PDF

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lab report for Bromination of trans Stilbene using pyridinium which is the 7th lab you are going to do in Chem 27200 lab...

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CHEM 26200 LAB # 7 Bromination of trans Stilbene using pyridinium

04/12/2021

Aim:In this experiment we will learn how the Pyridinium tribromide method is used for bromination and performed to create 1S and 2R 1,2-dibromo-1,2-diphenylethane from trans-stilbene.

Introduction :There are many organic compounds that have been identical in organic chemistry. Alkenes and Alkanes are some of those organic compounds. In addition, Alkenes go through a variety of reactions in organic chemistry, including halogenation, for example. Alkenes are unsaturated organic compounds with at least one double bond between two carbons. Since alkenes have a double bond, they are more reactive than alkanes. Moreover, Alkene halogenation reactions, such as chlorination or bromination, involve an addition of dihalides such as Br2 or Cl2 through the double bond of alkenes, causing the double bonds of carbon to be broken. One of these alkene halogenation reactions is bromination. However, the nucleophile double bond strikes the Br2 compound during bromination, causing the double bond to break. The bond between the two atoms is broken when the pi bond removes a bromine atom from Br2. The positive charge is stabilized by the cyclic bromonium ion, which prevents carbocation rearrangement. The other bromine atom was left off attacks from the back of the cyclic molecule, attacks from any carbon from either side, since the cyclic bromonium ion has a positive charge. Therefore, in this experiment, we will brominate trans Stilbene with pyridinium tribromide as a solvent to see whether the result has two bromine ions or not, since bromination produces meso-stilbene dibromide.

Physical Properties Table :Compound Name

Molecular Formula

Trans-Stilbene

C14H12

Structure

Molecular Weight

Melting and Boiling Point

Physical Appearance

Hazards

180.25 g/mol

M.P:122 to 125 C

white crystals

Harmful, could cause serious eye irritation.

1.14 g/cm3

B.P: 305 to 307 C

Cis-Stilbene

Ethanol

Methanol

C14H12

C6H6O

CH4O

180.25 g/mol

M.P: 122 to 124 C

1.04 g/ml

B.P: 307 C

46.07 g/mol

M.P: -114.1 C

0.7892g/ml

B.P: 78.37 C

32.04 g/mol 0.791 g/cm3

Pyridinium tribromide

1-bromobutane

1-chlorobutane

C5H6Br3N

C4H9Br

C4H9Cl

M.P: -98 C

Harmful, it causes respiratory tract, diarrhea, vomiting and nausea.

colorless liquid

Harmful, it causes eyes and skin irritation.

Colorless liquid

Harmful, it causes damage to organs through repeated exposure.

orange-redish crystalline solid

Harmful, it causes skin burns and eye damage as well respiratory irritation.

colorless liquid

Harmful, it causes eyes and skin irritation.

Colorless liquid

Harmful if swallowed and enters airways. It may cause drowsiness and dizziness.

B.P: 64.7 C

319.83 g/mol

M.P:127 to 133 C

1.03 g/cm3

B.P: 240 to 242 C

137.02 g/mol

M.P: -112 C

1.28 g/cm3

B.P:101 to 102 C

92.6 g/mol

M.P: 122 to 123 C

0.886 g/cm3

yellow oily liquid

B.P: 77 to 78 C

1-iodobutane

Silver nitrate

C4H9I

AgNO3

184.02 g/mol

M.P: -103 C

1.62 g/cm3

B.P:129 to 131 C

169.87 g/mol

M.P: 212 C

1.015 g/ml

B.P: 444 C

Colorless liquid

Harmful, it causes eyes and skin irritation and respiratory irritation if inhaled.

white solid and Colorless liquid

Very harmful, it causes skin burns and eye damage as well respiratory irritation.

Procedures :● We started our experiment by preparing our mixtures. ● We started by adding 10 milliliters of absolute ethanol and 250 mL of transstilbene into a erlenmeyer flask of 25 ml ● Then we put a magnetic stir bar into the bottom of the flask and turn it on to stir them and dissolve the solid. ● Then the heating plate would be turned on and we have to keep it up to 80 C because Ethanol boils at 80 C ( We would not let Ethanol to boil because we just want the trains to dissolve). ● After 10 mins waiting for the trains to dissolve, we will add 500 ml of pyridinium tribromide. ● As soon as we add pyridinium tribromide to the solution we will see how the color of the mixture will change from clear to orange mixture. We will also see a change of color when we add more ethanol, the color will change from orange to yellow. ● Afterwards, the mixture will be stirred for 5 to 10 mins. ● We will then use a clamp to detach the flask from the heat and switch off the heat plate. ● After that we will see that there seems to be a lot of white solid at the bottom, and an orange liquid floating on top.

● Then we wait a few minutes for it to cool off. ● When it cools down, we will see the various layers are more visible and perfectly shown.( if it did not cool down then we will put it in water bath and let it to cool for some time) ● Then after, we'll arrange the busher funnel and filtration to extract the white solid. ● We'll also put 10 mL Methanol in a good water bath for 5 to 10 mins to assist with the transition and the buchner funnel. ● Then, after making all compounds stay in the cold ice water bath for time shown above, we'll wet the filter paper with a small amount of methanol and swirl the combination compound to get it all into the buchner funnel. ● The flask will then be rinsed several times with some ml of methanol to ensure that all of the liquid is transferred to the buchner funnel. ● Then, we place the vacuum for 10 mins to rinse it out. ● While the majority of the liquid has evaporated, we will see some of it in the flask. ● After that, we would be able to see what products are forming along the edges, and we can see that the majority of the solid went through the Buchner tube, perhaps because it was already dissolved in the solvent. (some of the compounds that we may see are trans-stilbene or a substance like Meso-stilbene dibromide). ● The powder would then be transferred to a watch glass and allowed to dry if necessary. ● Once it has dried, we will determine its mass as well as its melting point and record it. (The starting compound Trans- stilbene melts at 122-125 C; while, Meso-stilbene dibromide, on the other hand, melts at 236-237 C). ● As a result, we will be able to tell whether the pouder is the substance and whether it is pure or not depending on the melting point.

Reactions of Halogenoalkanes:

● We start by filling each of the four test tubes with 2 ml ethanol and labeled them from A to D. (We would not use halogenoalkanes in test tube A because it's a sensor tube) ● We will add 3 or 4 drops of 1-chlorobutane to tube B. ● Then, we add 3 or 4 drops of 1-bromobutane to tube C. ● And we add 3 to 4 drops of 1-iodobutane into tube D. ● We will also put stopper tubes in each of the test tubes. ● Then, we put all of the test tubes in a water bath at 50 C for a few minutes to cool them down. ● Afterward, we will have to operate much harder than before, and each tube will receive 1 ml of silver nitrate solution. ( To guarantee that the substances are combined, we will start the stopwatch and shake the test tubes) ● After all of that, we would be able to see that tube D 1-iodobutane reacts quickly and produces a light yellow precipitate. ● As well as tube C we can see that 1-bromobutane has formed a white precipitate. ● And lastly, we can see that test 1-chlorobutane in test tubes A, and B reacted together to produce thin white precipitate.

Results :-

As our result, we arranged meso compounds 1S and 2R in this lab experiment, and the reaction from bromination gave us meso-Stilbene dibromide of trans-stilbene. However, we obtained meso-stilbene dibromide with a melting point of 238 to 239 C based on the findings of the experiment. However, if bromination occurs on cis-stilbene, we can end up with a combination of enantiomers, and Bromination would have a higher melting point than cis-stilbene because the steric hindrance, cis-stilbene is less stable, and trans-stilbene has a higher melting point than cis-stilbene. Therefore, we will use the Alkyl halide test to confirm if our bromination went successfully or not. In addition, the test will show us the thick white color precipitate because bromine atoms are in our product.

Conclusion :In this experiment, we were able to watch the videos and know the steps of what we had to do if the college was open. In addition, by using Pyridinium tribromide as the solvent, we were able to say that meso-Stilbene dibromide was

synthesized from trans-Stilbene by bromination. Moreover, we used an alkyl halide test with silver nitrate to know if bromine was present in our product or not. However, we determined our product's melting point, which was around 238 to 239 C. We used this melting point to determine whether we received a meso compound or a combination of enantiomers. However, we were able to use our results to calculate and get our final details. When we did the calculations, we found that the Percent Yield is 93.25%. However, for our safety we had to wear goggles and gloves to protect ourselves from harmful chemicals.

References :● Our lab manual ● Trans-Stilbene SDS- https://pubchem.ncbi.nlm.nih.gov/compound/trans-Stilbene-oxide ● Cis-Stilbene SDS- https://pubchem.ncbi.nlm.nih.gov/compound/cis-Stilbene ● Ethanol SDS- https://pubchem.ncbi.nlm.nih.gov/compound/Ethanol ● Methanol SDS- https://pubchem.ncbi.nlm.nih.gov/compound/Methanol ● Pyridinium tribromide SDS- https://pubchem.ncbi.nlm.nih.gov/compound/Pyridinium-bromide ● 1-bromobutane SDS- https://pubchem.ncbi.nlm.nih.gov/compound/1-Bromobutane ● 1-chlorobutane SDS- https://pubchem.ncbi.nlm.nih.gov/compound/1-Chlorobutane ● 1-iodobutane SDS- https://pubchem.ncbi.nlm.nih.gov/compound/1-Iodobutane

● Silver nitrate SDS- https://pubchem.ncbi.nlm.nih.gov/compound/Silver-nitrate...