CHEM
Experiment 5 lab report .docx

Experiment 5 lab report .docx - A Separation and...

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A Separation and Purification Scheme The objective of this experiment was to separate out a mixture of an acid, base, and a neutral compound and purify it using extraction, filtration, and recrystallization. The compound that was received consisted of 2-chlorobenzoic acid (acid), 4-aminobenzoate (base), and 1-4- dibromobenzene (neutral compound). When calculating the theoretical yield, it was determined that since 0.5g of the mixture would be used, there would be 0.25 grams of the benzoic acid, 0.20g of the 4-aminobenzoate, and 0.055g of the 1,4-dibromobenzene. The general solubilities of these compounds are shown in the table below: Compounds Water Methylene Chloride NaOH HCL Methanol 50% 2- chlorobenzoic acid insoluble soluble soluble insoluble Insoluble @room temp Soluble when heated 40% 4- aminobenzoate insoluble soluble insoluble soluble Insoluble @room temp Soluble when heated 10% dibromobenze ne insoluble soluble insoluble insoluble Insoluble @room temp Soluble when heated The process to separate out these compounds is to add 1M HCl to crash out the base, 4- aminobenzoate, in the mixture to turn the basic compound into an acid (4-aminobenzoic acid). The protonated amine then forms a salt which can be reversed with the addition of a base, in this
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case a high concentration of sodium hydroxide. 6M NaOH is used to precipitate out the base. Then the two compounds left in the mixture will be the acid and the neutral compound. The acid compound forms a salt when combined with a Bronsted base, in this case sodium hydroxide. 1 M NaOH is used on the 2-chlorobenzoic acid, which deprotonates the acid and becomes basic (2- chlorobenzoate). And when the acid is added to the aqueous layer which contains the deprotonated acid, the acid is re-protonated and becomes insoluble in water and therefore precipitates. In this experiment, 6M HCl is added to the ionic salt to precipitate the acid, so it can
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