Recrystalization+Lab

=Introduction:= Organic chemists often find themselves with compounds that are contaminated by small impurities. Most often the first approach to remove those impurities is through recrystallization. Recrystallization is a process that involves the following seven steps: the selection of a proper solvent, dissolution of the solute with solvent, decolorization of resulting solution, filtration of solids, crystallization of solute, collection and wash of crystals, and drying of purified product. The purification itself occurs during the crystallization process. Once a small crystal has formed, more crystals begin to grow from it. Since the compound that is being purified is in excess, its crystals form first leaving impurities in solution. After the compound is allowed to dry a small sample can be tested in a Mel-Temp apparatus to establish its purity. Nice job here.

=Procedure:= This experiment can be found here:

Higginbotham, Carol. "Crystallization and recrystallization." //Central Oregon Community College//. Web. 15 Oct 2010. <[]>.

Williamson, Kenneth L. //Macroscale and Microscale Organic Experiments//. p.56-63. 4th. Boston, NY: Houghton Mifflin Company, 2003. Print.

=Data and Analysis:= Table 1: The percentage of a given solute that dissolved in a given solvent Benzoic Acid formed needle-like Crystals, Anthracene formed needle-like crystals, Resorcinol formed plate-like crystals.
 * Experiment 1:**
 * ** Solvents ** |||||| ** Solutes ** ||
 * || **Benzoic Acid** || **Anthracene** || **Resorcinol** ||
 * **Toluene** || cold - 100% || cold - 0% || cold - 0% ||
 * ^  || hot - 100% || hot - 100% || hot - 100% ||
 * **Ligroin** || cold - 10% || cold - 0% || cold - 0% ||
 * ^  || hot - 50% || hot - 0% || hot - 0% ||
 * **Distilled Water** || cold - 0% || cold - 0% || cold - 100% ||
 * ^  || hot - 100% || hot - 25% || hot - 100% ||
 * Percentages recorded are an estimate based on observation

The best pairs were: 1.Water and Benzoic Acid - Benzoic Acid dissolved slowly at 90°C but recrystallized very quickly when taken out of hot water bath. 2.Toluene and Anthracene - Anthracene instantly dissolved at 93°C and slowly recrystallized over several minutes when cooled. 3.Toluene and Resorcinol - Resorcinol dissolved quickly at 95°C, recrystallized slowly at room temperature and quickly when placed into an ice bath. I appreciate the way you have summarized your results.

-Starting mass of Pthalic Acid=0.065g -Amount of solute added (Water)=about 15 drops -End mass of Pthalic Acid=0.042g -Percent Recovery=65% Calculation here is okay, sig figs okay. What did the phthalic acid crystals look like?
 * Experiment 2:**

-Flask with 0.252g of Norit Pellets became a slightly lighter brown color than original solution -Flask with 0.060g of Norit Pellets had no noticeable change in color than the original solution
 * Experiment 4:**

-Initial melting point of Aldol before it was recrystallized = 155-160.6°C -Starting mass of Aldol = 0.199g -Amount of 9:1 EtoH and water solvent to completely dissolve the Aldol = 9.95mL -Crystals formed almost immediately when the solution was placed into an ice bath. -Mass of recrystalized aldol = 0.083g -Percent yiled = 42% -The final recovery of aldol was a light greenish-yellow color, which began, before recrystallization, as a brownish yellow color. -The melting point of the recrystallized Aldol was 172-175°C Yay! You did a melting point on the starting material for comparison! Good thinking! =Conclusion:=
 * Experiment 7:**
 * __Experiment 1:__** The solubility of solutes in solvents is the first step in the process of recrystalization. In experiment 1 we tested three solutes with three different solvents to test the solubility. The primary goal was to determine which solutes dissolved in which solvents and if the solutes dissolved, what shape the crystals formed after they recrystalize. If the solute was not dissolved instantly, the mixture was heated to determine if heat could dissolve the solutes. Datat shows that Toluene was the most efficient solvent of the three used, dissolving all three solutes. Next was water which dissolved Resorcinol and Benzoic Acid. Ligroin was the least efficient solvent and only dissolved benzoic acid which was heated. After recrystalization, it was determined that Resorcinol formed needle-like crystals as well as Benzoic Acid and Anthracene formed plate crystals.
 * Sources of Error:** No sources of error are recorded in this section of the lab. oh, there are always potential sources of error. You may not know what happened, but the possibility is out there. For instance, what if your test tubes were dirty? What if the solvents were mislabeled? Long shots, I know, but the object here is to imagine what could conceivably lead your astray in your thinking. It's not about identifying error that you know about: it's about analyzing for the possibility of misinterpretation.


 * __Experiment 2:__** In experiment 2, background of the solubility informaton in experiment 1 was used to perform the next step in the recrystalization process. A solvent was determined to dissolve the solute Pthallic Acid, in this case, water was used as the solvent. The Pthallic Acid and water were mixed together and heated until solute was dissolved to eliminate impurities in the Pthallic Acid. Crystals were filtered out to give an end mass of product to be 0.042g of Pthallic Acid from the starting mass of 0.065g which calculates to a 64% yield.
 * Sources of Error:** During the filtration process, some of the crystals stayed attached to the sides of the reaction tube and were not recorded in the final mass of the product.

__**Experiment 4:**__ Decolorizing of raw sugar used another aspect in recrystalization in the process of a hot filtration. The decolorizing agent used were norit pellets. 0.252g of Norit Pellets were added to one sample and 0.060g were added to another sample. The observational data concludes that the addition of Norit Pellets to a dark brown solution of raw sugar water slightly removes some of the dark brown color; however, the change in the experiment performed was only very slightly noticeable.
 * Sources of Error:** No sources of error are recorded for this experiment.

__**Experiment 7:**__ The final recovery of Aldol after recrystallization was found to have a melting range that had increased roughly twelve degrees from the original aldol synthesized. Even though percent yield of the recovery was a little less than half, the final recovery was close to pure. As well, the final recovery of Aldol was a lightish-green color, showing that some pure substances are colored and therefore it is helpful to know what the final color of the pure substance is going to be in order to determine if there are impurities in the substance. Norit can then be added until the substance obtains the desired color of the final product.The process of recrystallization performed in this lab provided a near pure (complete) recovery, showing the method of recrystallization to be an efficient means to purify a solid product. **Sources of Error: C**rystals were lost in the first partial hot filtration when the solution was allowed to cool slightly and also to the wet filter paper (which crystals stuck to) used in the second hot vaccum filtration.

Post-lab question is missing.