Recrystallization Of Cinnamic Acid Lab Report

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Brominated hydrocinnamic acid underwent an elimination reaction (E2) to produce cinnamic acid. The goal of the elimination experiment was to remove the bromine and a hydrogen from brominated cinnamic acid, using the strong base KOH, to produce crude cinnamic acid. The reaction is shown in Scheme 1.
The crude cinnamic acid was dissolved then recrystallized. The goal for recrystallizing crude cinnamic acid was to purify the acid and filter out any impurities. Recrystallization is one method used to purify a compound. Using a hot solvent, the compound is dissolved. It is then cooled to produce pure crystals. “As the crystal develops, impurities are excluded from the crystal lattice, thereby completing the purification process.”1 The key to recrystallization is the solvent used. “The solute must be relatively insoluble in the solvent at room temperature but much more soluble in the solvent at a higher temperature. At the same time, impurities that are present must either be soluble in the solvent at room temperature or insoluble in the solvent at a high temperature.”2 The solvent must be able to dissolve the product and the impurities for recrystallization to take place. Once dissolved, the solution cools first to room temperature before placing it in an ice bath, for “gradual cooling is conducive to the formation of large, well-defined crystals.”2 Once cooled, the solution is placed into the ice bath to further the recrystallization of the compound. The crystals are then

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