Organic Chemistry 1: Identifying a Constituent of “Panacetin” full Lab report

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- Objective The objective of this lab was to purify the unknown isolated at the end of the last lab by recrystallization and establish its identity by determining its melting point. - Description a... nd theory of: i. Recrystallization During recrystallization, a given solid substance is purified by dissolving it in a boiling solvent and is subsequently allowed to re-solidify in an ice bath. Once crystals have formed in the solution, it is filtered using vacuum filtration in order to isolate the crystals. In some cases, the boiling solution is also filtered using gravity filtration, to remove impurities that do not dissolve1 . This procedure purifies substances, since the impurities present in the original solid do not solidify in the ice bath and are washed away during vacuum filtration2 . To make the purification effective, the substance that is being purified should have a low solubility in the solvent it is being dissolved in at low temperatures, but a good solubility in it at high temperatures3 . This difference in solubility makes it so that the substance will dissolve when boiling, but when it is cooled the solubility will decrease, forcing the substance to crystallize into a purer form. ii. Mixed melting-point The melting point of a substance describes the range of temperatures a substance will melt and become a liquid. When a substance is contaminated, its melting point will decrease. This is because, since there is a certain amount of impurity in the substance, the molecular structure of the substance will be weaker and thus easier to dissolve when exposed to a source of heat4 . Additionally, the range of temperatures over which the substance will melt before becoming liquid will be larger. The temperature range will be broader because the concentration of impurity in the given substance is not uniform. In other words, the impurity is concentrated in [Show More]

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