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Read this entire laboratory procedure before starting this lab.
PART I Preparation and Purification of Aspirin
It is often desirable in the chemical laboratory or in industry to produce a natural substance by
the chemical reaction of two or more other materials. When a chemical reaction occurs, new substances are produced that have different physical and chemical properties. This process of producing the new substance is called chemical synthesis.
Once a material is prepared, it usually is somewhat impure. It may contain some unreacted
starting material or unwanted by-products, which were unavoidably produced in the chemical reaction. One way of purifying solid materials is a process called recrystallization. The impure solid is placed in a liquid in which it is insoluble when cold, but soluble when hot. The mixture is heated and the newly synthesized material along with the impurities dissolves. When the mixture is allowed to cool, the desired material reforms into crystals again, but the impurities remain dissolved in the solvent. Thus, the new solid crystals are purer than the original. Sometimes the procedure is repeated with a fresh portion of solvent to rid the solid of even more impurities.
Aspirin is produced by reacting salicylic acid with acetic anhydride in the presence of a little
salicylic acid acetic anhydride aspirin acetic acid
This is a good example of the reasoning used by chemists. The salicylic acid itself is what
actually works in the body, but it should not be taken orally since it will burn the mouth and throat lining. The aromatic -OH group causes this burning. In aspirin, the aromatic -OH group is "blocked" by being bonded to the acetyl group and less damage is done while digesting. Then in the upper intestine the acetyl group is removed to produce salicylic acid, which is absorbed into the blood. Equipment:
Procedure for Part I Synthesis of aspirin
Weigh 5 g of salicylic acid in a 250 mL flask. Add 10 mL of acetic anhydride and 10 drops of
concentrated H2SO4 (CAUTION: if any acid is spilled wash with plenty of water immediately). Swirl
the contents in the flask for 5 minutes and allow to stand for 10-15 minutes. Cool the flask in an ice-
water bath then add 50 mL of cold water to the flask. Break up the solid mass with a spatula or glass-
stirring rod. Suction filter the mixture to remove the water. Pour the filtrate into the Aqueous
Solutions from Aspirin Synthesis
container in the hood. The solid can be blotted between paper
towels for a few minutes to remove most of the moisture. Purification of Aspirin
To purify, remove the aspirin from the filter paper and add it to 20 mL of ethyl alcohol,
C2H5OH, in a 250 mL flask. Heat the contents of the flask on a hot plate to cause the crystals to dissolve. When all of the solid has dissolved, pour the hot solution into 30 mL of dH2O at room temperature. If the solution becomes cloudy immediately, heat on a hot plate until it becomes clear.
Set the clear solution of aspirin aside to cool slowly and observe the formation of the crystals.
After the mixture is cooled and crystals have formed, place the flask containing the aspirin in an ice-
water bath for 15 minutes. Suction filter the liquid from the solid, and place the isolated aspirin in your
drawer to dry for a couple of days. Pour the filtrate into the Organic/Aqueous Solutions from
container in the hood.
Before the next lab period, weigh the dry product and record its weight and percent yield along
with the appearance of the product and any observation during the reaction. Determine the melting point of your dry purified aspirin and compare it to the literature melting point.
Perform the Fe3+ test for phenols (aromatic alcohols) on your purified aspirin and the starting
material, salicylic acid by placing a few crystals of the appropriate solid in a test tube containing about 5
mL of dH2O. Add two drops of 1% FeCl3 to the test tube and mix. Record your observations and
conclusions. Pour the test solution into the Solutions from Aspirin Phenol Test
container in the hood.
PART II Esters
Many of the characteristic flavors of foods are due to the presence of small amounts of organic
compounds called esters. They are detected by the smell sensors in the nose while the food is being chewed. Thus common experiences of taste and smell are the result of chemical activity. The tongue also has taste sensors for a limited number of tastes. What we call flavor of a food is a combination of the various smells and tongue taste sensations which result when chemicals in the food interact with the chemicals in the nose and tongue tissue. Equipment:
Alcohols: methyl, ethyl, pentyl, and octyl
Acids: butanoic, acetic, anthranilic, and salicylic
The following five esters can be easily prepared in the laboratory by reacting an alcohol with an
organic acid. The formulas, reactions and amounts are given below
In a test tube place the amounts of the alcohol and acid indicated for a particular ester (1 mL ≈
20 drops). Add two drops of concentrated H2SO4 and mix. Heat the contents in boiling water bath for
a few minutes being careful not to boil away all of the newly synthesized ester. After the test tube has
cooled to room temperature, cautiously smell the contents by wafting the vapors toward your nose with
your hand. Dilute the ester by placing a few drops in 200 mL of water and smell again. Does the
nature of the smell depend on the concentration of the ester? Which ester should produce a positive
test for phenols? Check your hypothesis. What are the structural differences between aspirin and
wintergreen? Place all the synthesized ester solutions into the Synthesized Esters Lab
container in the
butanoic acid ethyl alcohol ethyl butanoate
acetic acid pentyl alcohol pentyl acetate
salicylic acid methyl alcohol methyl salicylate
anthranilic acid methyl alcohol methyl anthranilate
Name _______________________ Date PART I
Fe3+ test for phenols: Observations and Conclusions
Name _______________________ Date PART II Ester Preparation O
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2010 Three-Tier Prescription Drug List Reference GuideTable of Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6 Prescription Drug List - 2010 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-25 Anti-Infectives Antibiotics