TITLE
: 1) EXPERIMENT 1 (RECRYSTALLIZATION OF VANILLIN) VANILLI N) : 2) EXPERIMENT 2 (MELTING POINT DETERMINATION)
NAME
: ATHIRAH BT. ABDUL KAMIL
(2007116909)
LAB PARTNER
: NURADHAM NURADH AM FARHANA BT. ZALI
(2007116741)
GROUP
: ASD4Bn
COURSE
: DIPLOMA IN SCIENCE
DATE OF THE EXPERIMENT : 13 DATE OF REPORT SUBMISSION
RD
JULY 2009 & 3 : 10
TH
RD
AUGUST 2009
AUGUST 2009
OBJECTIVES
:
1. To purify the vanillin by recrystallization procedure and to determine the recovery percentage. The purified vanillin samples will be evaluated through melting point on the next experiment. 2. To take melting point using the capillary tube.
PROCEDURE
:
1. 2 g of vanillin was weighed into a 120 ml Erlenmeyer flask. 2. About 50 ml of water was added to the flask and was stirred vigorously. 3. By using Bunsen burner, the solution was heated just to the boiling point and stirred until all the vanillin dissolved. 4. The flask was placed in an ice bath for about 5 minutes and was stirred occasionally. 5. A fitted piece of filter paper was placed properly in Buchner funnel by making sure that all the holes were covered. The paper was being wet by deionised water from wash and the vanillin crystals were vacuum- filtered. 5 ml of ice-cooled water was used to rinse the Erlenmeyer flask twice and the same water was used again to wash the crystals in t he funnel. 6. The crystal was emptied onto a weighed piece of filter paper and was placed in the desk for drying purpose for about three weeks and being sure that it cannot spill. 7. The automatic melting point determination machine called Mel-Temp apparatus was used to measure the recrystallized vanillin and crude vanillin melting point. 8. The capillary tube was filled by crude vanillin sample which was pressed at the open end until there was about 0.5-1cm length of sample in the tube. 9. The capillary tube was dropped; the end sealed went down through a 1m piece of 6mm glass tubing that was being held on a hard surface. 10. The impact of capillary with the hard surface seldom resulted on breaking and caused the sample to drop to the bottom of the tube. 11. The dropping procedure was repeated until the sample was packed in the bottom of the tube. 12. The capillary tube was at tached with the Mel-Temp apparatus holes. The start button was pushed when the plateau light was on along with the ramping light. 13. Procedure 7 until 11 was repeated for the recrystallized vanillin sample. The sample was grounded in a mortar before it was press ed at the open end of the capillary tube. 14. The temperature for both samples was recorded in the table.
DATA & OBSERVATION
:
PROCEDURE 1. 2 g of vanillin weighed into 250 ml Erlenmeyer flask.
2. 3.
Stir 50 ml of water in the flask. The solution heated with Bunsen burner until boiling point and stir until all vanillin dissolved. 4. Stir the solution in flask that placed in ice bath for 5 minutes. 5. A piece of wet filter paper fitted to the Buchner funnel. The vanillin was vacuum filtered. The Erlenmeyer flask was rinse twice with ice-cooled water along with the crystals. 6. The crystals emptied onto a weighed filter paper and placed in the desk to dry. 7. The automatic melting point determination machine called MelTemp apparatus was used. 8. The capillary tube filled with recrystallized vanillin at the open end until there is about 0.5 1 cm sample length. 9. The capillary tube was dropped through 1 m piece of 6 mm of glass tubing held on hard surface. 10. The impact caused the sample to drop to bottom of the t ube 11. Then we put the capillary tube in the hole of Mel-Temp apparatus.
12. Fill the capillary tube with crude vanillin.
RESULTS
:
OBSERVATION A crystal of vanillin was weighed on a weighing machine. We obtained 2.0021 g of vanillin and 0.3755 g of filter paper. The crystal of vanillin was dissolved incompletely. The crystal of vanillin was heated and the colour change from white to colourless. The vanillin dissolved completely. After stirring the solution for 5 minutes the precipitate present. The filter paper must stick to the Buchner surface. At this stage, the tap water must be opened all the time to let the water flow. We make sure that the crystal dry in Buchner flask.
The dried crystals + filter paper in a petry dish for 3 weeks The apparatus was set up as in the manual.
The recrystallized vanillin was grind in a mortar to make powder so that it is easier to be pressed to the open end of the tube. The powder in the capillary tube was dropped until it reached the bottom of the tube. The powder length in the tube after the impact was 1 mm. Then we put the capillary tube in the hole of MelTemp apparatus. When the plateau light is on, we pushed the start button. After that the ramping light is on too. When the temperature reached 80 the powder start to melt. Then when it reached 83 it liquefies completely. This is because it contains impurities as there is presence of foreign matter in it. Finally we let the sample cool to room temperature. The procedure for recrystallized vanillin is the same for crude vanillin. When the temperature reached 81 the crude vanillin start to melt. Then when it reached 83 it liquefies completely. Finally we let the sa mple cool to room temperature.
RECRYSTALLIZED VANILLIN RESULT
:
DATA Mass of crude vanillin Mass of empty filter paper Mass of recrystallize of vanillin + filter paper Mass of recrystallize of vanillin
MELTING POINT DETERMINATION RESULT
READING 2.0021 g 0.3755 g 2.1774 g 1.8019 g
:
DATA Melting point of crude vanillin Melting point recrystallized vanillin
PERCENT RECOVERY
READING 81 - 83 80 - 83
:
Mass of recrystallized vanillin x 100
=
1.8019 g x 100
Crude vanillin
2.0021 g =
90% pure vanillin
=
10% loss
1 1% - 10% impurities 90% of the recrystallized vanillin is pure vanillin while 10% of the recrystallized vanillin is the impurities. This shows that although we vacuum filter the solution but the impurities still able to escape.
Q UESTIONS AND ANSWERS
:
1. What is the percent recovery? The percent recovery is 90% pure vanillin, so the loss is 10%.
2.
3.
4.
5.
6.
Why is the vanillin solution cooled in an ice bath before vacuum filtration? The vanillin solution was cooled in an ice bath before it underwent vacuum filtration because the solution is usually cooled with an ice bath to further decrease the solubility of solid in the solvent thus; resulted to the crystallization. How does the recrystallization procedure remove solvent soluble impurities? The solvent soluble impurities was removed in the recrystallization procedure by underwent filtration. As the solubility decreased, the temperature dropped and the solid crystallizes back out upon cooling. These impurities pass through the final cold filtration. What additional step should be added to this procedure to remove impurities insoluble in solvent? The additional step that should be added to this procedure is by including gravity filtration of the hot solution to remove the insoluble impurities. Gravity and vacuum filtration separate insoluble solids from a liquid phase. The choice depends on conditions. Suggest criteria you would apply to choose b etween them. Gravity filtration is the most commonly used filtration technique. The use of filter paper in this type of filtration allows gravity to draw liquid through the paper. A small piece of filter paper will absorb a significant volume of liquid. This technique is useful when the volume of mixture to be filtered is greater than 10 ml. On the other hand, vacuum filtration is much faster than the gravity filtration and is most often used to assemble solid products resulting from precipitation or crys tallization. This technique is used primarily when the volume of liquid is being filtered more than 1 -2ml. As a conclusion, I would choose the vacuum filtration. This is because it will filter impurities greater than the gravity filtration and it saves time as it operates much faster than the g ravity filtration. Suggest any ways you can think of improve any parts of this experiment? In my opinion, there is a part of this experiment that can be improved like we can remove insoluble impurities that are present by hot filtration. Besides that, we should watch the dissolution process carefully to avoid using too much solvent and risking poor recovery of the purified solute. On the other hand, to keep liquid from flowing over the top of the funnel, we make sure the top of the paper should not extend above the funnel by more than 1 2 mm. Compare your answer with literature melting point of 81 - 83 of vanillin, 7. comment on the purity of the crude and recrystallized vanillin and also the success of your recrystallization. The melting point for the crude vanillin is within 81 - 83 while the melting point for the recrystallized vanillin powder is 80-83 . At 80, the recrystallized vanillin powder started to melt while at 83 the powder is liquefying completely. It means that the sample is impurities because there is a foreign matter present. So our recrystallization is quite successful.
DISCUSSION OF RESULTS
1.
:
The first experiment is recrystallization of vanillin. Its purpose is to purify the vanillin by recrystallization procedure and to determine the percentage. The purified
vanillin samples will be evaluated through melting point on the next experiment. Vanillin, methyl vanillin, or 4-hydroxy-3-methoxybenzaldehyde, is an organic compound with the molecular formula C 8H8O3. Its functional groups include aldehyde, ether, and phenol. It is the primary component of the extract of the va nilla bean. It is also found in roasted coffee [ Wikipedia Online Encyclopaedia]. ] The technique used in the experiment are the selection of the appropriate solvent, dissolution of the solid to be purified in the solvent near or at its boiling point, formation of crystalline solid from the solution as it cools, the filtration of the purified solid that will be iso lated and drying the c rystals [Gilbert & Martin, 2002 ]. In this experiment, we need to weigh the vanillin crystal which is put on the weighing paper in the weighing machine to get the mass of the vanillin crystal. The mass of vanillin crystal is 2.0021 g. Then we heated the vanillin crystal in 250 ml Erlenmeyer flask which added with distilled water that act as a solvent. We use Erlenmeyer flask instead of a beaker because beaker is not a suitable vessel for recrystallization because it has a relatively large surface area to which recrystallized product may stick thus; lowering the efficiency of recovery. We need to heat the vanillin crystal because as the solvent temperature increased, the solubility of solids in liquids will increase significantly too. Furthermore, almost all solids are more soluble in a hot than in a cold solvent [Gilbert & Martin, 2002 ]. After stirring the solution for 5 minutes the precipitate present. The extent to which the solid precipitat es depends on the difference in its solubility in the particular solvent at temperatures between the extreme used. When we vacuum filter the vanillin, the tap water must be opened all the time to let the water flow. We make sure that the crystal dry in Buchner flask so that it will not drip. We let the crystal in the desk to dry for three weeks before we further to the second experiment. The second experiment is melting point determination. Its purpose is to take melting point using the capillary tube. The melting point of a substance means the temperature at which the liquid and solid phases exist in equilibrium with one another without change of temperature. However, if impurities present in a substance the melting points will be compromised. The presence of impurities will decrease the melting point of a pure solid [Gilbert & Martin, 2002]. In this experiment, we managed to obtain the melting point for the crude vanillin which is 81 - 83. However, the melting point for recrystallized vanillin is 80 - 83 . The per cent recovery for recrystallized vanillin is 90% pure vanillin while the other 10% is its loss. This happened because the sample is impurity as there is some foreign matter present in the sample. The purity of compound or the pure compound is a homogenous sample consisting only of molecules having the same structure. So, it could be that the recrystallized vanillin is impure due to the presence of contaminants like paper fibre from filter paper [Gilbert & Martin, 2002]. The
difference of the melting point between crude vanillin and the recrystallized vanillin is 1 equivalent to 1% - 10% loss. While conducting these experiments, some errors occurred like in the first experiment we did not plaster the Buchner funnel to the Erlenmeyer flask properly. This has caused the loss of water pressure inside the flask. So, to overcome this problem, we redo the plastering by plastering it tighter than before. Besides that, in the second experiment we did not stay near Mel-Temp apparatus when the temperature of recrystallized vanillin exceed to 80 thus; we get quite a large range of temperature reading compared to the crude vanillin temperature range. So, we redo it by using new capillary tube filled with recrystallized vanillin and stay near the Mel-Temp apparatus until we managed to get the tempera ture correctly.
CONCLUSION :
From the experiment, I can conclude that the purpose of this experiment is to purify the vanillin by recrystallization procedure, to determine the recovery percentage and to determine the melting point by using capillary tube. The melting point for recrystallized vanillin is 80 - 83 while the temperature for crude vanillin is 81 83. The percent recovery is 90% pure vanillin while the other 10% is its loss.
REFERENCES:
1. Gilbert C. J, Martin F. S, Experimental Organic Chemistry A Miniscale and Microscale Approach, Third Edition, Thomson, 2002. 2. http://www.wikipedia.com
