Bromination of trans-cinnamic acid

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In this lab we'll look at what its like to add bromine to transcinamic acid via adding methods of stereo-chemistry. Additionally we'll take a look at trying to prove the reaction was successful and that we actually did get 2,3-dibromo-3-pheylpropanoic acid.Bromination are a type of Halogenation procedures using bromine, read more about it here.





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 Below is kind of a generalized look at the addition of the Bromine via a Trans Addition, which sorry to spoil the surprise is the way its going to add.

Trans-cinnamic acid (E-3-phenyl-2-propanoic acid) has a molecular weight of 148 g/mol and a melting point of 133 degrees Celsius.

There are several enantiomers of 2,3-dibromo-3-phenylpropanoic acid, they all have a molecular weight of 308 g/mol (Molecular Weight: 307.96662 to be specific).

The (2R, 3S) and (2S, 3R) have a melting point of 202-204 degrees Celsius.

The (2R, 3R) and (2S, 3S) have a melting point of 93.5 to 95 degrees Celsius.



 Things that were done:

150 mg trans-cinnamic acid and .6 mL glacial acetic acid were put acid in a test tube. The tube was put in a 50 degree celcius water bath till all the trans-cinnamic acid dissolves. Next 1.0mL of 1.0M Br2 in acetic solution. the mix was stirred via agitation at 50 degrees Celsius till the color faded from red/brown to light orange and was heated for another 15 minutes. Next a drop of cyclohexane was added. The mix was cooled in ice water bath for 10 minutes (crystals formed). Meanwhile distilled water was cooled (in an ice bath). Note if the crystal didn't form the side would have been scratched with a siring rod and left in the ice water bath for another ten minutes.

The product was collected via vacuum filtration. The crystals were washed with ice water ( note its a good idea to do it till the smell of acetic acid is gone. Next was the process of recrystallization. The sample retrieved from vacuum filtration was placed in .5mL ethanol in an 10mL Erlenmeyer flask. After the sample had dissolved boiling stick was added and the mix was heated via a steam water bath. If the sample doesn't dissolve add more ethanol. Next a volume of water equal to the amount of ethanol was added. The sample was removed from the heat and allowed to cool for 10 minutes in ice. Crystals were removed from the solution via vacuum filtration (note a new clean Hirsch funnel and new filter paper was used)

 Things you may ask...

What is a mixed solvent recrystallization? What is the reason for using mixed solvent recrystallization?

 Mixed solvent recrystalization refers to a process of crystallization used for the purpose of purification. A solvent is added to a mixture with desired and undesired components creating a solution. The solution is heated so that all of its components are able to dissolve, this solvent chosen because of its known properties of solubility. At a higher temperature everything should remain dissolved in the solvent as it becomes supersaturated. However as it cools crystals of your desired compound should form being that at lower temperatures the solvent can no longer remain super saturated, meanwhile impurities and undesired compounds should remain dissolved in the solvent. In this experiment the crystals could be isolated via vacuum filtration.

 Should the product exhibit optical activity?

 No the product would not exhibit optical activity because while each enantiomer is chiral they exist as a racemic mixture such that the specific rotation of one enantionmer would cancel the rotation of the other being that they should have the same magnitude but in the opposite direction.

 What is the mechanism of the addition like?

It can happen via a concerted mechanism (Shown below)

It can happen via Radicals

What can the melting point/range say about the purity of the sample?

 If the observed melting point or range is near the reported melting range from the literature it suggests that  the product is that of the enantiomer set. For this particular experiment the  (2R,3S) and (2S, 3R) enantiomers of 2,3-dibromo-3-phenylproanoic acid are expected. Indicating that the bromine addition occurred via an anti method. Had bromine of added via syn addition the melting point would have been near 95 °C (provided in the literature).  The difference of several degrees between the literature and the experimental values may be the result of impurities and the possible existence of other enantiomers or compounds in the product. Recall that impurities cause depression and extend the range of the melting points.

Fun?

Please excuse the dorkish moments...

Meet Metta World Peace formerly known as Ron Artest.

 Shall we go to Paradise?

 Because ortho sounds like some root word related to bones, here is another one.

Some more attempts at funny.

Limonene

Limonene exists in R-(+) and S-(-) formations. Both have a boiling point of 175.5-176 degrees Celsius, both have a molecular weight of 136.2 grams per mol but they differ in their optical rotation. 

R-(+) has a density of about .8402 g/mL and an optical rotation of 125.6 degrees (note the positive number) while the S-(-) has a density of .8407g/mL and an observed optical rotation of -122.1 degrees (note the negative number)

In this lab we'll talk about Isolating the R-(+) formation of Limonene from orange peels. Note the R-(-) can be found in Caraway seeds.

How you do it?
Take the oranges and peel them. It's best to do this right away to prevent the loss of limonene. Try to remove the white pulp from the peel.

In a blender add the peels and 200- 250 mL of water. After blending put in a 500 mL round bottom flask. Add 4 drops of anti foaming agent...or don't if you would like to have a "fun time". With a Claisen adapter prepare for steam distillation with a 50 mL round bottom flask as the receiver. Marking the 50 mL round bottom flask at the 35 mL level will be helpful so pour some water in it, mark it, empty it and voila.

Boil the mix without letting any solid material bump over into the condenser. Collect 35 mL of the distillate. Note if you use a heating mantel a variac will probably be a good idea as to add an element of control. Also it will prevent the mantel from heating up to quickly/getting to hot and in the process you may actually end up burning your orange peels. Burning the orange peels may result in bad results and a load of gunk that accumulates on the bottom of the round bottom flask which take my word will be annoying and nasty to clean up however a bit of acetone, some soap and some time will help you eventually make it clean again. Also the burned peels may affect your observed optical rotation adding an element of impurity to the sample.

Pour the distillate into a separatory funnel (125 mL size should do). Add 5 g sodium chloride and shake. Next add 10 mL dichloromethane via a conical funnel through the top of the separatory funnel. Gently shake the mix and allow for pressure to be release by opening the stop cock every so often. Let the mix sit and the layers to separate. Make sure the stop cock is closed during this process and the stopper is held is place or else by by sample.

Collect the bottom layer (the organic bottom layer and the top is the top aqueous layer) in a flask. Repeat the extraction with 15mL dichloromethane (fresh) every time. Next dry the extracted solution with anhydrous magnesium sulfide for 10 min.
Meanwhile weight and clean an Erlenmeyer flask for later use. Into this Erlenmeyer with the use of a conical funnel fitted with filter paper and pour the solution. This should take out the anhydrous magnesium sulfide.

Then by any means you want be it nitrogen gas, hot water bath or just allowing it to sit allow the dichloromethane to evaporate.

To do polarimetry (link should take you to wikipedia) obtain 10mL of 95% ethanol. Dissolve Limonene in 3 mL of the ethanol via Pasteur pipette. Transfer to a 10mL volumetric flask and do polarimetry on it. Note calculate the polarimeter with the 95% ethanol as the reference solution. The rotation should tell you about entantiomeric excess if applicable.

Questions:

 What is a steam distillation?  Why is it useful in this isolation experiment?

            Steam distillation is a form of distillation often used to distill heterogeneous mixtures. It allows for the adding of pressures of components in the mixture to overcome that of the atmosphere and boil. This typically results in lower temperatures till boiling is reached especially so when compared to a solution that follows Raoults Law.

            Steam distillation is useful in this experiment because it lowers the temperature necessary to give rise to the boiling of limonene. Typically to achieve this point the boiling point would be so high the orange peels would burn and the charring would contaminate the isolated limonene. The H20 and limonene pressures combine give rise to the lowered boiling point. It’s also possible that higher temperatures would result in decomposition of limonene.

 What was the purpose of the extracting of our collected distillate with dichloromethane and salt-water?

            The salt in the salt water allows for more transfer of limonene to the organic layer. The salt is absorbed in the water and saturates it decreasing the total possible amount of limonene that can be absorbed by the water. Similar to a process called "salting out".

            If the dichloromethane was used for extraction the Limonene would have been found in this layer. Because dichloromethane is more dense than water and they do not mix the dichloromethane would have formed a visible layer below the water that could be taken out by opening the stop cock of the separatory funnel and allowing the bottom layer to be collected.

How do I find the specific rotation?

specific rotation = observed rotation                                                                       
                               (density in g/mL) x length of polarimeter tube in decimeters

Or in words its the observed rotation divided by the product of the density (aka concentration) and the length of polarimeter tube in decimeters.

What happens if you shake too vigorously during the extraction with dichloromethane?

The gas could explode due to the build up of pressure inside of the separatory funnel. Also you may mix the layers so well that it won't separate as quickly.


On the other hand what happens if you don't shake vigorously enough?
The layers may not separate and limonene may not separate from the aqueous layer and go into the dichloromethane layer.

As always I don't get paid for this so if you can please join below I really appreciate it.

Alcohol...lets make some.

So this isn't the best way to make alcohol I guess but still never the less its alcohol...lets make some. Specifically we will be synthesizing ethanol by fermenting sucrose with the help of some yeast. Ethanol is also known as Absolute alcohol, Alcohol, Drinking alcohol
Ethyl alcohol, Ethyl hydrate, Ethyl hydroxide, Ethylic alcohol, Ethylol, Grain alcohol, Hydroxyethane, Methylcarbino. Go here to learn about ethanol.

General Information:

What we are going to talk about.
C2H22O11 plus H2O breaks into 2 C6H12O6 plus zymase gives us 4 CH3CH2OH (ethanol) + 4 CO2

Place 40 mg sucrose in a 500 mL Erlenmeyer, add 200 mL water and 3.0 g dry yeast. Stire till sugar dissolves and you can't really see the yeast.

Add 35 mL Pasteurs salt - stir to mix. Close the flask with a stopper fitted witha  piece of bent glass tubing.

Fill a test tube halfway with a saturated Ca(OH)2 (also known as limewater) - submerge other end of glass tube into test tube so its about 1 cm below surface of the solution. Store for a week.

After a week come back and filter the solution via vacuum filtration in a 500 mL filter flask. Rinse flask with water. Now take the filtrate in the Erlenmeyer and place in a round bottom flask, add 2 boiling stones and assemble for simple distillation. Set so the Alcohol flows into the recieving flask at 1 drop/sec. Heat till 50 mL are collected.

To find the density of this weight a tared 10.0 mL erlenmeyer, add 10.0 mL of the distillate and mass/volume = density which corresponds with a percent alchol by volume.

Take the sample (all of the simple fractional distilation sample) and prepare for fractional distillation. Use a 100 mL round bottom flask, add some boiling stones. In the Fractional distillation either pour some glass beads or stainless steel sponge. Turn heat to moderate amount and wait.  Collect 3 different samples each called Fraction 1, 2, 3 etc.

Fraction one should be the first 10 mL sample, Fraction 2 is the sample from 78 to 80 degrees Celcius and Fraction 3 is really rubish.

To determine the percent alcohol by volume or by mass use the same technique as above. Take a known volume, find its mass. Mass divided by volume = density. Use tables or online literature valus to find the percent alcohol by volume by the corresponding density. Remember water is more dense than alcohol. Hence water sits below alcohol if you pout them together. Ideally you would want your sample to weigh less.

Questions

What does the density and percent composition results tell you about the relative efficiencies of simple vs. fractional distillation? In other words, the distillation efficiency is higher when the distillate density is _________ and percent ethanol is ______________.

Blank 1) lower Blank 2) higher

Distillate from simple distillation does not have as high of percent alcohol as those of fractional distillation, hence fractional distillation has a higher efficacy. When distillation efficacy is higher the density of the solution is lower and its alcohol content is greater.

2. Which method gives purer ethanol? Briefly explain reasons for the difference in efficiencies of these two distillation methods, assuming no large technical errors were made.

Fractional distillation should result in purer ethanol. The difference is in part due to difference in apparatus, which provides more surface area to allow for cooling and condensation of the sample, the increase in plates and allow to get closer to the azeotrope.

3. How does the recorded temperature relate to the composition of the distillate?

The lower the boiling point of the solution the greater the likelihood that there is more ethanol in the solution. Ethanol has a lower boiling point than water, hence it is more volatile. Temperature and composition are directly related because the boiling point is contingent upon the compsition of the solution and the more volatile substances boil first.


4)What is an "Azeotrope"?
Its where you have liquid and vapor with same boiling point so no more enrichment can occur via distillation.

5) What makes fractional distillatation more efficient that simple distillation in terms of the aparatus. Being that in this case the two liquids have a similar boiling point.

The distillation column makes fractional distillation more efficient. Its filled with glass beads or steel wool. This elongated column allows for more surface area fr vapor to become cool and in liquid form again. Then it heats up again. Allowing for more plates (cycles of warming to vapor and being cooled again).
In each plate (heating till vaporazation till cooling and retuning to liquid form via condensation) in falls down back the fractional distillation tube the percent alcohol actually increases till the azeotrope is reached because both liquids have simlar boiling points they go through the same states.

Check out this image it may help.

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