Crystallization Report Objective: the objective of this lab is to introduce the technique of crystallization. Background: The chemicals used in part A were Sulfanilamide and Ethyl alcohol. Sulfanilamide(C6H8N2O2S), or sulfonamide antibiotic, functions by competitively inhibiting enzymatic reactions involving para-aminobenzoic acid (PABA). PABA is needed in enzymatic reactions that produce folic acid which acts as a coenzyme in the synthesis of purine, pyrimidine and other amino acids.
In part C, Fluorene was dissolved in three solvents. Fluorene(C13H10) is a polycyclic aromatic hydrocarbon. It forms white crystals that exhibit a characteristic, aromatic odor similar to that of naphthalene. It is combustible. It has a violet fluorescence, hence its name. For commercial purposes it is obtained from coal tar. Results: In part A, . 30g of impure Sulfanilamide was placed in a beaker, and heated 95% ethyl alcohol was added to just cover the crystals. This was then heated and swirled vigorously until all is dissolved.
Then remove and let cool slowly, while covered with a watch glass. Then it was placed in an ice bath to further crystallization. After crystallization is completed, a vacuum filtration system was used to separate crystals. These crystals were then dried, weighed, and melting point was determined. Table 1: percent yield and melting point of Sulfanilamide Starting weight| Weight recovered| Percent yield| Melting point| . 30g| . 23g| 76. 7%| 164-165oC| This percent recovery is not 100% for several reasons.
The sulfanilamide is not 100% pure to begin with, some of the sulfanilamide was dissolved in the mother liquor, and also because of a small spillage of the crystals from the filtration step. Part C of this lab was performed by first finding the best solvent for Fluorene. This was done by testing water, toluene, and methyl alcohol by adding 6mL of solvent to . 3g of Fluorene. It is then shaken, if it dissolves immediately like it did with Toluene, the solvent is too good. If it does not dissolve immediately, then it is placed in a hot water bath.
If it does not dissolve after the bath like with water as the solvent, it is not a good solvent. After it has dissolved let it cool, then place in an ice bath. After crystallization occurs, create a vacuum filtration system to separate crystals, and then dry and weigh the dry crystals. Finally, the melting point was found. solvent| reaction| Starting weight of fluorine (g)| Final weight of fluorine (g)| Percent recovery and melting point| Water| No reaction| . 296| | | Methyl alcohol| | . 313| . 046| 14. 6% mp= 164-166oC| toluene| Immediately dissolved | . 306| | |
The percent recovery for fluorine was only 14. 6%, this may be attributed to a side reaction that did not precipitate out of the solution, as well as some human error. the experiment was done correctly so the percent recovery must be low due to a side reaction that did not go to completion within the solution, leaving much left in the mother liquor. Conclusion: the percent recovery in part A dictates that the experiment was done successfully although there were some crystals were left behind. Part C of this lab was not as successful as the percent recovery of Fluorene was only 14. % in methyl alcohol. Discussions: this experiment was easy but our data came out skewed because we had to redo the experiment because crystals did not initially form in any of the solvents in part C. Crystallization techniques will be used often and are useful for future labs. The percent recovery in part C was low due to the solute lost during the reaction in the mother liquor, as well as some lost due to the vacuum filtration system tipping over. This lab helped in the understanding of the importance of crystallization techniques.