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Organic Chemistry Lab

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Extraction & Evaporation. Separating the Components of "Panacetin, and the

Recrystallization & Melting Point Measurement. Identifying a Component of "Panacetin."

Introduction

This laboratory experiment was a combination of two separate experiments as stated in the above title. The introduction has been split into 2 separate components to briefly give some background on each procedure.

1

This particular lab is set up with quite a different scenario then that of the last one.

A roving agent for the ASP Corporation has recently Panacetin, which is an analgesic drug. The agent looked carefully at the bottle and it said that they were produced in the United States, but he later noticed a few discrepancies on the bottle and even the tablets themselves which causes a concern that they may be counterfeit.

The label on the bottle posted the ingredients per tablet as aspirin (200 mg), acetaminophen (250 mg), and sucrose (50 mg). Sucrose is used so that children have an easier time ingesting the tablets. The basis of this lab was to see whether the tablets are as pure as they read on the bottle or whether there is another component that is a chemical relative of acetaminophen, either acetanilide or phenacetin, as well as to find out the percent composition of aspirin, sucrose, and the unknown makeup in the tablet. Both acetanilide and phenacetin fight pain just as effectively as acetaminophen, but both are banned in the United States because of having amounts of toxicity that forbids them from being sold in this country.

2

The purpose of this part of experiment is to purify and identify the unknown component of Panacetin from the first experiment. Separation techniques are never perfect, so there should be at least some impurities expected within the substance that has been separated from a mixture. Therefore, some kind of purification procedure is needed to extract them. Solids can be purified in a number of ways such as, chromatography, recrystallization and sublimation; liquids usually have to be purified by distillation or chromatography. From information of the previous experiment, it is known that acetaminophen and phenacetin are relatively soluble in boiling water but relatively insoluble in cold water. This suggests that the unknown component of Panacetin could possibly be purified by the process of recrystallization (an impure solid is dissolved in a hot solvent and then crystallizes when the resulting solution is cooled to room temperature. From data gathered in experiment number 2, the volume of water needed to dissolve the mass of either acetanilide or phenacetin can be estimated. Phenactetin is less soluble in boiling water, so it will need more water to dissolve. The process of recrystallization should commence with a small amount of water and then only adding another small amount if the compound doesn't dissolve in the previous amount at boiling point.

After purification of a compound it should then be analyzed to confirm its identity and amount of purity. To do this, a simple melting point measurement can be suitable enough for a compound whose physical properties are already known. This method is useful only for those compounds that are composed of only a small number of substances. The identity of the compound can often be determined by mixing the unknown with an authentic sample of each known compound and measuring the melting point of the mixtures. This test shows that when a pure compound is mixed with a different compound, then the different compounds melting point will lower and broaden. The melting point of a compound can also give an insight into the degree of its purity. If a compound melts over a narrow range (~2 degrees Celsius or less) at room temperature close the lit. value, it is probably quite pure. If its melting point range is broadened and substantially lower than the lit. value, it is probably contaminated by water or other impurities.

My hypotheses for both parts of this experiment are: 1) The composition of the panacetin as stated on the label is not same, and 2) the identity of the unknown component of panacetin will be acetanilide.

Methods & Materials

1) See "Separating the Components of Panacetin" in Lehman's Operational Organic Chemistry Lab Manual. (Pgs. 31-32).

2) See page 36 of Lehman's Operational Organic Chemistry Lab Manual

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