The Partition Coefficient (Kp)30: Extraction of Benzoic acid and its Conjugate Base from Two Immiscible Phases PDF

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Experiment VI: The Partition Coefficient (Kp)30 Extraction of Benzoic acid and its Conjugate Base from Two Immiscible Phases

Abstract: The purpose of this experiment was to extracttbenzoictacid and sodium benzoic acid, its conjugate base, from two immiscible phases. The extraction is formed from the solution of benzoic acid in methylene chloride, the organic layer, mixed with deionized water during Part A. In Part B, the solution was extracted with sodium bicarbonate instead, the aqueous phase. After separation and extraction of the organic layer, anhydrous sodium sulfate was added to help dry out the water. Evaporation of the two tubes in the hot sand bath revealed the amount of benzoic acid that was dissolved in methylene chloride and its ratio was used to calculate the partition coefficient. Procedure: The separation, extraction, drying, and evaporation of the benzoic acid in each layer to determine its partition coefficient was completed with the given steps from the Poulos, Z. J., “Extraction f Benzoic acid and its Conjugate Base from Two immiscible Phases31”, in Organic Chemistry I- A Laboratory Manual for the Health Science Major,” Fall 2019; Hayden-McNeil: Plymouth, MI, 2018, pp 103-111. One milliliters of methylene chloride was used during the experiment rather than 600L of methylene chloride as stated in the procedure. No other changes were made. Reactions: Reaction of Benzoic Acid with water-no reaction

Benzoic Acid

Water

Benzoate

Hydronium Ion

(Acid)

(Base)

(Conjugate Base)

(Conjugate Acid)

Reaction of Benzoic Acid with base

Benzoic Acid

Sodium Bicarbonate

Sodium Benzoate

Carbonic Acid

(Acid)

(Base)

(Conjugate Base)

(Conjugate Acid)

Data: Experiment: Part A Benzoic Acid (Original Mass) 0.073g Culture Tube (Mass) 11.645g Benzoic Acid in Culture Tube 11.703g

Experiment: Part B 0.064g 11.636g 11.688g

Recovered (Mass) Benzoic Acid Recovered

0.058g

0.052g

(CH2Cl2) (Mass) Benzoic Acid remaining in

0.015g

0.012g

Aqueous Layer (H2O) (Mass) Kp Partition Coefficient

3.867g

4.333g

Discussion and Conclusion: This experiment consisted of Part A, where benzoic acid was dissolved with methylene chloride and deionized water, and Part B, where it was mixed with methylene chloride and sodium bicarbonate. Since benzoic acid is a nonpolar compound, it would be more soluble with other nonpolar compounds, which means there should be a greater amount of benzoic acid recovered in Part A rather than Part B. The results do not pair up with the predictions since a higher amount of benzoic acid was recovered from Part B. The results from

both parts are very close, could be due to human error. In Part B, the drying agent was not used and the extra mass could have came from extra water droplets. When comparing the IR spectrum, a carbonyl group can be found at 1678 with a carbonyl stretch of a (C=H) bond and a single carbon-hydrogen bond around 3000....