rin organic report 1.
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! !!! " # Name
: Nurul Syareena Binti Mohd Nor Azman
: Nadia Binti Mohd Rustham Siti Hajar Mohd
: Dr. Zurina
Date of experiment
: 17th January 2011
Date of submission
: 24th January 2011
"$ To isolate caffeine from a tea bag.
%c Caffeine is one of the groups of xanthines compound. It is a water soluble compound and an active ingredient that contain in tea and coffee. It is an alkaloid which is a naturally occurring compound that belongs to the group of xanthines containing nitrogen and having the properties of an organic amine base. The advantages of the xanthines are it can stimulate the central nervous system and the skeletal muscles. The stimulations result in an increased of alertness, the ability to put off sleep and an increased capacity of thinking. However, caffeine cannot be taken in an excessive amount. It will cause to restlessness, irritability, insomnia and muscular tremor.
Cellulose is the main component in the tea leaves. It is virtually insoluble in water. Thus, it will be easier to isolate. However, if the caffeine in the tea is extracted with a hot water, other substance which also soluble such as tannins in water will be extracted out together with caffeine. When tannins are extracted into hot water, some of these compounds are partially hydrolyze to form free gallic acid. If the sodium carbonate is added to the tea water, these acids are converted to their sodium salts which are highly soluble in water. Thus, the only caffeine required cannot be obtained. Therefore, organic solvent is used to isolate caffeine from tea. It is because caffeine is much more soluble in organic solvent compared to water. In this experiment, dichloromethane as the organic solvent will extract the caffeine from the tea water and left behind the sodium salts of gallic acids and the tannins in the aqueous layer.
Extraction process is used to isolate the caffeine from tea. In extraction, two liquids which are insoluble in each other are used. A separatory funnel is the device used in this extraction. For this experiment, the separated dichloromethane layer is the layer that contains the caffeine. A rotary evaporator is used to separate the caffeine from the dichloromethane. It will required product and distill of the solvent. By using the product produced which is caffeine, the
melting point of the caffeine will be determined by using the mel- temp apparatus. The standard melting point of caffeine is 227-228 °C.
&' ' %c The tea leaves which have been removed from the tea bag were weighed. 50 mL of water in 100 mL beaker was heated until it almost boiling. Another tea bag was used to place in the hot water so that it lies flat on the bottom of the beaker and was covered completely as possible with water. The heating process was continued for about 15 minutes. Next, the hot tea solution was transferred into a 100 mL conical flask. 0.5015g of sodium carbonate was added to the solution. The solution was cooled to room temperature before proceed to the next step. Then, the solution was filtered into a 50 mL separatory funnel by using cotton not filter paper. 15 mL of dichloromethane was added to the separatory funnel. The solution was shaking gently to avoid the formation of foam. The solution was let to stand for a while to separate the organic and dichloromethane layers. After that, the lower dichloromethane layer was drained off into 100 mL beaker. The extraction was repeated 2 times with another portion of 10 mL dichloromethane. The dichloromethane layer was dried by adding anhydrous sodium sulphate excessively. The dried dichloromethane solution was transferred into a pre-weighed 50 mL round bottom flask. The solvent was evaporating off using a rotary evaporator. Then, small portion of the solid produced was taken to determine the melting point of caffeine.
c % " ï? Weight of tea leaves
: 2.1330 g
ï? Weight of Na2CO3
: 0.5015 g
ï? Weight of empty round bottom flask
: 44.3927 g
ï? Weight of round bottom flask + caffeine
: 44.4393 g
ï? Weight of caffeine extracted
: 0.0466 g
ï? Melting point of caffeine
: 222 °C ± 230 °C
ï? Weight of caffeine extracted from tea bag: = (weight of round bottom flask + caffeine) ± weight of empty round bottom flask = 44.4393 g ± 44.3927 g = 0.0466 g
ï? Percentage of caffeine in the tea: = (weight of caffeine extracted ÷ weight of tea leaves) × 100 = (0.0466 ÷ 2.1330)g × 100 = 2.18 %
In this experiment, caffeine was isolated from the tea leaves by extraction. The tea leaves
were immersed into a hot water so that the caffeine and other substances which are soluble in water were extracted into the water. After that, the solution was cooled to room temperature and a drying agent, sodium carbonate which is basically basic was added to the solution. The caffeine contains in the water was then extracted by using organic solvent, dichloromethane. This is because of the caffeine which is more soluble in dichloromethane rather than the water. Therefore, the caffeine was isolated from the tea water by extracting with dichloromethane and the other substance remained in the aqueous solution. In the separatory funnel, the aqueous solution was on the top layer and the dichloromethane solution was on the bottom layer. The solution was separated based on the density of the solution. In this case, the dichloromethane have higher density than aqueous solution. A rotary evaporator was used to separate the caffeine in the dichloromethane solution. The rotary evaporator was distilled off the solvent and remained the solid, caffeine in the flask. The weigh of the caffeine obtained is 0.0466 g. The melting point of the caffeine was determined by mel-temp apparatus. The small portion of solid caffeine was transferred in the capillary tube and was placed in the mel-temp apparatus. From the experiment, the melting point of caffeine is 222- 230°C. The value obtained is in the range of the theoretical melting temperature which is 227- 228°C. The percentage of caffeine in the tea bag was calculated by using the data obtained from the experiment. As shown in the calculation, the percentage of caffeine in the tea bag is 2.18 %.
The caffeine was isolated from the tea bag by extracted with dichloromethane. The
percentage of the caffeine in the tea bag is 2.18 %. The melting temperature of the caffeine from the experiment is 222-230 °C.
( )c *? + ,-! #, !!! . /0*c !1,- ! - -1,-2+3* H2O aqueous layer
Extract 3x with Na2SO4 H2O
3*? (-41 -5+, / 555/6 Sodium carbonate was added to the solution because, when tennis are extracted into water, some of the compounds are partially hydrolyze to form acid. Therefore, the addition of sodium carbonate helps the acid to convert to their sodium salts which are highly soluble in water.
*? -,+5, !! 5! - ##*(-46 The green tinge color is due to the chlorophylls pigments and the respective oxidation product.
±*? (- / !1-4-#!4+ 5 , !! 4/1- - +7 +.3°C)? This may because of the isolated caffeine produced by the experiment was containing other elements which cause the caffeine not 100% pure. Thus, lower the melting point of the caffeine.
*? (- 1+5- -, !!!-+/ 1!5 -,+6 At atmospheric pressure, more heat is needed for the sublimation reaction. As more heat is absorbed, it will be an imperfect separation. For a good separation, the lower the pressure is needed.
8 1.? D.L.Pavia, G.M.Lampman, G.S.Kriz, R.G.Engel, Introduction to Organic Laboratory Techniques, 2nd ed., Thomson Brooks/Cole, Canada, page 78±89, 698±706, 713-714. 2.? James W. Zubrick, The Organic Chem Lab Survival Manual, 7th ed., Wiley, United States of America, page 127- 136, 197-200.