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list of experiments
Solubility book (3rd Edn)
Paris Dayon Favors II
To recrystallize caffeine using the high boiling point solvent 1-Octanol and then washing with the low boiling point of solvent pentane from a .75
Created a .77
solution by adding 1-Octanol to .25 grams of caffeine in a test tube. The solution was then heated by a heat gun evenly and stirred by a spatula ship until all of the crystals went into the solution. Once dissolved, the solution was then cooled at room temperature for recovery start of the crystals. The solution was then put into an ice bath from an 150 ml beaker to speed up the recrystallization process. The recovered crystals were then filtered through suction filtration and washed twice with 1-Octanol. An additional filtration was done on the crystals and then washed with pentane. The crystals were analyzed by HNMR and melting point to determine its purity.
The crystals from Sample 1 were recovered.
Amount: 0.183 g (from .2513 g)
Appearance: White crystals
(Melting point will be calculated once the machine is working again)
for Sample 1
Purity: A very pure sample of anhydrous caffeine with a trace amount of 1-Octanol still remaining from the sample.
Picture #1: A picture of the solution of anhydrous caffeine and 1-Octanol in test tube 1.
Picture #2: A picture of the recyrstallization of the solution within the first three minutes of cooling down after being heated. This was the very start of the process.
Picture #3: A picture of the filtration system including the sinter glass funnel, flask, rubber stopper, and air suction tube.
Picture #4: A picture of the ice bath containing Sample 1 for the speeding up the recrystallization process.
The sample was conducted in a test tube for the experiment, limiting the amount of the sample that could be recovered using a sizable scupula for retrieval. However, test tubes used for the method show for a better purity. Therefore, it is mainly used to gain the highest purity of the solution and not the highest yield.
The temperature dependent solubility curve for caffeine in 1-octanol predicted that the crystals of the 0.75M solution would enter the solution at 127°C and this was an accurate prediction. The crystals were observed to enter the solution at 135°C. Once cooled at room temperature and put in an ice bath for rapid crystallization, the 1-Octanol recrystallized with the crystals. However, using suction filtration to separate the 1-Octanol from the crystals and washing the remainder with pentane, it was an effective demonstration. Impurity of the sample was but a trace, supporting this method for future experiments.
The recovered 0.183 g of caffeine was a 73% yield to the projected 90% percent. Much of the sample was lost due to the transference from a small test tube to the filtration system. The purity of the sample increased as suspected, but the yield for the sample did not follow suit. To limit the loss of sample, a method to retrieve the recrystallized sample from the test tube by smaller sized means than a scupula will be put in place.
The NMR determined that the caffeine was pure and was compared to the NMR of pure caffeine found
The recrystallization should be used in a test tube to prevent heavy loss of the sample and the method of suction filtration should be used to optimize the purity of the solution with 1-Octanol. 73% of the .77
solution was recovered demonstrating that it is a successful form of recrystalllization.
10:28 Weighed test tube 1: 11.4612 g.
10:30 Added 0.2513 g of caffeine anhydrous to test tube 1.
10:35 Added 1.2505 g of 1-Octanol to test tube 1 by pipette.
10:49 Took Picture #1 of test tube 1 (test tube cap to be remained off while heating).
10:52 Inserted spatula ship into test tube 1 as boiling indicator.
10:54 Applied low heat evenly to test tube 1 from the heat gun.
10:57 Turned off the heat gun due to signs of boiling and stirred the solution with the spatula ship.
10:58 Continue to heat solution at low heat evenly.
11:01 Turn off heat gun due to the crystals dissolving all into solution and wait for recrystallization (solution reached a temperature of 150C).
11:04 Took Picture #2 of test tube 1, as recrystallization started to process.
11:11 Created ice bath in 150 ml beaker for test tube 1.
11:15 Placed test tube 1 into ice bath to speed of the recrystallization process.
11:23 Prepare filter flask for filtration.
11:25 Took picture #3 of filtration system ready for suction.
11:26 Administer as much crystals able from test tube 1 into the filter using a scupula.
11:28 Start filtration process using air suction.
11:41 Stop filtration and weigh flask with 1-Octanol in it after filtration of the solution: 86.973 g.
11:47 Wash filtered 1-Octanol flask with acetone to dry.
11:49 Weigh dry flask to determine the amount of 1-Octanol obtained through first filtration: 86. 253 g.
11:57 Wash test tube 1 with 1.2083 g of 1- Octanol and administered into filtration system.
12:02 Wash test tube 1 for second time with 1.2450 g of 1-Octanol and administered into filtration system.
12:11 Filtered crystals on sinter glass funnel using suction filtration.
12:31 Wash the crystals with pentane by turning off the vacuum, pipetting the sides of the funnel with pentane, mixing the crystals in the pentane using the scupula and reapplying the vacuum. This was completed three times for three washes. After the final wash, the crystals were left on the vacuum to completely dry the pentane.
14:10 The weight of the sinter glass funnel with the crystals was 57.1443 g. The weight of an empty 5-dram vial was 11.9535 g. The crystals were transferred from the funnel to the 5-dram vial. The weight of the vial with the recovered crystals (sample 1) from the funnel was 12.1365 g. This means that there was 0.183 anhydrous caffeine crystals recovered from sample 1.
10:05 0.0251g of dried anhydrous caffiene from sample 1 was placed in a 5-dram vial and dissolved with 0.5 ml of CDCl3. The solution was put into the NMR.
NMR Tube 1 was analyzed by 500MHz HNMR and the file was saved as ONSEXP347_Sample1.
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