So you have a chemical unknown...

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Feel free to try this out if you have a chemical unknown it might help!

Welcome to the Organic Compounds Database.

This 2483 compound database has been compiled by Harold M. Bell at Virginia Tech. Fill in the form below with as much information as you can. Leave the information blank if you don't know or you don't care. Click on the submit button to execute your search. You will receive at most 20 hits.

Melting Point +-5C________________ Boiling Point +-5C
Index of Refraction, nD20 +-0.005_ Molecular Weight +-2amu
Formula: C H N O Cl Br I S
(for formulas you can enter a ">" or "<" in front of the number, eg. >2)

UV Absorption Wavelengths:

, , +-5 nm

Mass Spectral Peaks:

, , , m/e

Chemical Types:

No Carbonyl present_ Carbonyl present
No Aromatic present_ Aromatic present
No OH or NH present OH or NH present
CH type:
no C-H saturated C-H unsaturated C-H both saturated and unsaturated C-H Compound name contains:

Key to the Literature References
This data is available with 2D-structures and NMR chemical shifts in ISIS/Base format.

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.

Anyways if you are bored and or broke as always go here:

Purification of Caffeine and Analysis

Well who would have thunk it last post we started to ponder how do I get chlorophyll out of my extracted sample...this post we solve this issue.....Eh it may go a little sum sum like dis.

How about some free coffee and or tea before we start?

For your entertainment: Purification and Thin-Layer Chromatographic Analysis of Caffeine

Purpose
  The purpose of this experiment was to continue the study and purification of caffeine isolated in a previous experiment via sublimation and Thin Layer Chromatography. Molecules are shown below.

 
Stuff about Stuff
Caffeine: Look at the previous post. If you're too lazy just know that its a white powdery substance in its natural form without odor and a rather bitter taste.

Chlorophyll a: For now just know that it provides a greenish color.
 

Procedure

All procedures were carried out under a hood, all individuals involved wore nitrile gloves and safety goggles. Glassware was cleaned, rinsed with deionzed water and if necessary acetone before usage.

 

Safety like it or not it's important. If you haven't heard about Carol....here she is. She never wore her safety goggles and now she doesn't need them. Don't be Carol. Or even worse meet Bill (Maturity warning....). Don't be Bill.

  Prior to the beginning of this experiment a sample of caffeine extracted from tea leaves and was stored in a 25 mL Erlenmeyer flask that was corked and allowed to sit for a week. From this crude extracted sample a small mass was put into a test tube and about .1 mL dichloromethane was added to it. The test tube was covered with wax paper and allowed to sit. This sample was labeled “Crude solution” and was to be used for the Thin Layer Chromatography later in the experiment.
The remaining crude sample was put into a filter flask with a side arm, and 1.9 mL of dichloromethane was added to it. A filter adapter was then set in the filter flask and a test tube was placed so that it sat about .5 cm off the bottom of the filter flask. The filter flask was placed in a 100 mL sand bath so that the sand covered a few mm of the flask wall. The sand bath was connected to a transformer to allow for control in process of heating. To add stability and decrease movement of the equipment the flask and test tube were each clamped separately to vertical rods in the hood. The side arm of the filter flask was connected via appropriate tubing to the vacuum in the hood. The vacuum was turned on the check for any leakage of air, once it was clear there was none, the sand bath and vacuum were both turned on until it seemed that no more caffeine was collecting on the inner tube. Meanwhile the ice water was placed into the test tube (fitted in the filter flask) kept being replaced every few minutes. After both the sand bath and vacuum had been turned off, the equipment was taken off the sand bath and raised in the air to cool.

            A spatula was used to scrap the caffeine off the test tube and onto the weigh boat. The weigh boat was weighed prior to and after the addition of the caffeine. The sublimed caffeine was put into another test tube where.50 mL dichloromethane was added. The test tube was labeled “Purified solution” and was covered with wax paper and stored.

  For the TLC a developing chamber was created (shown to the left). A 150 mL beaker was fit with filter paper, placed in beaker so that it sat on the sidewalls of the beaker but made contact with the bottom. 5 mL of ethyl acetate were added and the chamber was covered with aluminum foil. While the chamber was being set up the TLC plate was prepared for spotting of different caffeine solutions. The TLC plate was 6.7 cm in length and 4.5 cm in width. A 2 mm line was marked from the bottom edge of the plate and another about 1 cm from the top. The line at the bottom was divided into 3 distinct marked areas.

            Using a micropipette 3 spots of the crude caffeine solution was placed in the center of the first area, 3 spots of the purified caffeine were added to the second and then 1 spot of the standard solution provided to the class was placed onto the plate. The TLC plate was then placed in the chamber and the ethyl acetate mobile phase was allowed to run. Note tweezers were used to handle the TLC plate upon entry and extraction of the plate from the chamber. The plate was then taken out when the ethyl acetate was near the line marking 1 cm from the top.  Immediately after the plate was taken out of the chamber and how far the ethyl acetate traveled was marked with a pencil. The plate was then analyzed with 254 nm UV radiation. During this process each spot of caffeine was outlined with a pencil and the chlorophyll was marked. Rf values were calculated for each caffeine solution by dividing the midpoint of the caffeine spot by the total distance traveled by the ethyl acetate solvent in cm. What we got the Rf value for the “Crude Caffeine Solution” was .121, for the “Purified Caffeine Solution” the Rf value was .144 and for the “Standard Caffeine Solution the Rf value was .124. .

Things that may be good to know.

Rf values = Distance between midpoint of spot from origin in cm

                        Distance traveled by the solvent in cm

 
 Questions? (Feel free to add your own)

So how does one see the results of the thin layer chromatography?
The visualization technique used in the TLC portion of this experiment involves the use of
ultraviolet (UV) light. The caffeine absorbs the UV light and gives off visible light.
This phenomenon is called fluorescence. For more on wiki go here.



Bored? Go here 

Its Question Time:

What is sublimation?And why is it useful in lab settings involving purification?

Sublimation is the process of a phase change between solid and gas. In general, if an experimental
product can sublime, one can use it as a purification technique. This is because in most cases, impurities do not sublime.

Caffeine and sublimation

 Caffeine will normally sublime around 180 degree C (at 1 atm).

In general, in order for a solid to sublime, its triple point pressure must be higher than 1 atm. In order to accelerate the sublimation process for caffeine (see below), external pressure must be reduced to drive the equilibrium towards gas phase. Vaccum filtration helps by lowering the pressure inside the filtering flask  and will promote the caffeine to sublime at a temperature well below 180 degree C.

Extraction of Caffeine from Tea

Maybe before you start your lab how about some free coffee? check this out





Introduction and Purpose    The purpose of this lab was to extract caffeine from tea. The molecular structure of the of caffeine the molecule of interest for the extraction, caffeine, is shown below.

Facts about Caffeine (maybe even fun facts): 
In its pure form its a white substance that melts at 236 degrees Celsius. It is an irritant and is considered toxic. Tea is said to be about 3% caffeine by weight, but it ranges across teas.
Caffeine can be found in coffee, energy drinks, tea (clearly, hence its used in lab), No doz, Midol and more!



Techniques used:
Vacuum Filtration, use of micro pipettes funnel, centrifugation and  use of drying agents








Procedure

The procedure used for the lab varied from the exact directions listed in the Lab Manual. This section will provide the procedures carried out, including the alterations from the manual. Aside from centrifugation the procedures were all carried out under a hood, all individuals involved wore nitrile gloves and safety goggles. Glassware was cleaned, rinsed with deionzed water and if necessary acetone before usage.
First the contents of 2 tea bags were put into a 150mL beaker. The mass of the tea was about 4.681 grams. Then about 2.50 grams of Calcium Carbonate were added followed by . 50mL water.
The mixture was boiled on a hot plate on a medium heat level, during this time period a watch glass was placed on the top of the beaker. After 10 minutes of boiling the mix was set on the bench top to cool so that it was warm to the touch.

During the cooling period a 5-cm Buchner funnel was put inside a 125mL filter flask with an arm that could be connected with proper tubing to a vacuum. The funnel itself had a piece of Whatman No. 54 filter paper inside that had been wetted slightly. Additionally a clean 150mL beaker was filled with 12mL water (measured with a graduated cylinder) and the 12mL level was marked with a piece of tape, the water was poured out. While no picture was taken of the lab set up the image below shows the set up despite the use of an adapter as shown in the image.



 The remaining solution was put through the filter and vacuum apparatus that was assembled during the cooling period. The vacuum was turned on and was allowed to run until filtered solution stopped coming out of the funnel tip and a pool of solution sat at the bottom of the flask (indicating that all the sample had gone through). The filtered sample (from the flask) went into the beaker that had the 12mL mark.
The sample was boiled shortly using a hot plate till it was reduced to the 12mL mark. The sample was then allowed to cool on the bench top till it was warm to the touch.
The sample was transferred to a 15mL centrifuge tube with a screwcap, 2mL of dichloromethane were added to the solution (dichloromethane is also known as Cl2CH2).
The solution was shook for about a minute and put in the centrifuge for about a minute. Upon completion of centrifugation 2 layers of material became apparent. A brown layer said to contain tannins and other materials and a green layer at the bottom containing the caffeine dissolved in the dichloromethane. A pipette was used to extract the green organic layer, which was placed in another centrifuge tube. Another 2mL of dichloromethane were added to the solution, the tube was capped, solution shook, centrifuged and the portion of the solution containing the caffeine was extracted with the pipette again. The process of adding 2mL dichloromethane, putting the cap on the tube, shaking, centrifugation and removal of the green layer was conducted a total of 4 times. After the 3rd centrifugation the layers did not separate in a distinct fashion, a small amount of sodium chloride (NaCl) was added to aid the process. The layers separated in a more distinctively, the organic layer was removed then the final set of preparation, centrifugation and extraction was completed.

Next anhydrous magnesium sulfate (a drying agent) was added to the tube with extracted dichloromethane and caffeine solution. This mix was allowed to sit for about 5 minutes with occasional swirling till the mix became clear. Then a microfunnel was prepared by tightly packing small piece of cotton at the tip of the pipette where it began to taper. It was clamped to a vertical bar in the hood such that it was about half way into a 25mL Erlenmeyer flask.
The dichloromethane and caffeine solution were transferred to the micropipette via a clean pipette and was allowed to go through the microfunnel and go into the clean 25mL Erlenmeyer flask. The remaining magnesium sulfate in the centrifuge tube was rinsed with .5mL dichloromethane so all contents could go through the microfunnel.

Above are magnified caffeine crystals

The 25mL Erlenmeyer flask containing the filtered solution was placed on a heat plate on a relatively low heating level, allowing for the dichloromethane to evaporate. The flask was removed once a dry dark green residue formed at the bottom of the flask and all the dichloromethane seemed to have evaporated. The flask was allowed to cool on the bench top. Then the sample was weighed. The percent recovery was then calculated by dividing the recovered mass of caffeine by the initial amount. Once everything was completed a cork was placed tightly on the flask and the sample was stored to be used for another lab experiment.  For clean up the tea was thrown in the trash being that they are not hazardous. Materials remaining from the extraction were put in the non hazardous waste bin. Meanwhile the centrifuge tube that previously had dichloromethane was left on its side to allow all dichloromethane to evaporate fully and then was rinsed. All glassware were cleaned with soap and water, dried, and given a quick rinse with deionized water.

Questions (Feel free to ask more, heck I'll even try to answer them for free!)


Why was the tea boiled (in water)? Turns out caffeine is actually highly soluble in hot water and it turns out boiling the tea leaves in hot water allows for the caffeine to be released. Hence we are able to extract the caffeine from the water later in the procedure.


Why is the aqueous tea solution cooled to 15-20°C before the dichloromethane is added?

The boiling point of CH2Cl2 is 40C water boils higher than this. If dichloromethane gets too hot, it emits highly toxic fumes of phosgene.  Now would be a great time to say that dichloromethane is actually kind of dangerous and acts as an irritant to the respiratory system (that thing you breath with). If heated to decomposition in flame or hot surface to form toxic gas phosgene and corrosive mists of hydrochloric acid are also formed. AND YOU GET TO BREATH IT IN!!!!!! YAYYYYY!!!!! To quote MSDS " Continued exposure may cause increased light-headedness, staggering, unconsciousness, and even death. Exposure may make the symptoms of angina (chest pains) worse"GO HERE TO FIND OUT MORE Oh yeah and I forgot its probably carcinogenic too....keep it cool and keep safe.

Now you may ask what is MSDS? They are Material Safety and Data Sheets. Home page is http://www.msds.com/ go there to learn stuff about stuff.


Why is the tea solution cooled before dichloromethane is added? Think of adding sugar or salt to water, water has higher solubility levels for many compounds at higher temperatures that can even allow for super saturation. But while it cools the solubility and the ability to hold the caffeine decreases as the temperature drops. Slowly but surely the caffeine becomes undissolved and then we add the dichloromethane to add the process of extraction.


How do I calculate percent recovery of the extraction of caffeine from the tea leaves?
 

Percent Recovery =   amount recovered   =  Insert mass of what you got     x  100% = % recovery

                                    Initial amount *            what it should have been

* Note as stated earlier tea is 2-5 % caffeine by weight, so unless you know the exact number multiply the mass of how much tea you started with by 3.5% to see the total caffeine you could have been able to extract. Don't be surprised if this number is rather low.

Why does adding salt (NaCl) to the aqueous layer sometimes help break up emulsions that may form in an extraction?
Hmmm...not sure of this one but here is my guess. NaCl is pretty soluble in water. And emulsions by definition are non polar substances surrounded by polar substances. Fun fact mayonnaise is an emulsion (True life I'm a food network dork). The NaCl will attract these water molecules deterring them from dealing with the emulsion. It helps provide a stronger inter phase between solutions too! Also adding salt can cause salting out.

In the event you used 1-Propanol and Salt

NaCl is used as a salting out technique to increase the dielectric constant of the water layer. By doing so, 1-propanol will separate out from the salt water and this allows the extraction of caffeine into the 1-propanol layer. In order for the 1-propanol to separate out from the water layer, the water must be saturated with NaCl. This can only be achieved if NaCl is added in excess amount.
When salt is added to the water layer, it decreases the solubility of caffeine. This is due to the fact that caffeine is only slightly polar in nature. Thus, the solubility equilibrium will now shift to the 1-propanol. This will cause the partition coefficient to decrease.

In the event you added Calcium Hydroxide. Here is why.

Calcium hydroxide helps to precipitate out the tannic acid as calcium tannate in tea leaves. If
sodium hydroxide is used instead, no precipitate will form (sodium tannate is soluble in water). The caffeine crude product will be contaminated with the tannate salt. And that would be a annoying


Caffeine is a white powder, why the hell is my sample GREEN!!!!?????
The sample is green because well lets face it you extracted it from tea...Tea is a plant. Plants have chlorophyll. Chlorophyll is green. Turns out you probably have chlorophyll in your sample. Tune in some other time and maybe I'll have a way...or do a lab that finds a way to eliminate and purify the extracted caffeine.

Why do we centrifuge in the caffeine extraction?
 You will use a centrifuge in this experiment break up emulsions once they form, separating the aqueous and organic liquid emulsion. Now you may ask what is an emulsion? An emulsion is a suspension of one liquid as droplets in another (the two liquids must be insoluble in one another). Think water in oil or oil in water they don't really mix. To avoid them, you can shake mixtures of insoluble liquids gently and add salt to aqueous layers remember that salting out thing you did by adding NaCl.


Meanwhile if you're bored feel free to visit and join.



What is the role of sodium carbonate in the extraction of caffeine in tea leaves? and also what is the principle involved in extraction?
The sodium carbonate acts as a base - you could use sodium hydroxide instead. When you boil tea leaves tannins dissolve in the water as well as the caffeine. If you do not use a base the tannins will also be extracted into the solvent (i.e. methylene chloride) used in the subsequent extraction . The base converts the tannins into their sodium salts - being ionic these salts are not soluble in solvents like methylene chloride so remain in the aqueous layer during extraction. This allows purer caffeine to be extracted.