Question

06 Lab 3a Separation.pdf

Question 1 of prelab

Explain in a few sentences how extraction can be used to separate an organic compound from sodium chloride.

Prelab 1. Explain in a few sentences how extraction can be used to separate an organic compound from sodium chloride. 2. Why is the CH2Cl2 layer the bottom layer in a CH2Cl2 / aqueous NaHCO3 extraction? In this experiment, what does the CH2Cl2 layer contain? What does the aqueous NaHCO3 layer contain? 3. In general, how does the solubility of a compound in a given solvent change with temperature?

Answer 1

1. The main principle of solvent extraction is the partitioning of compounds between two immiscible liquids. To an aqueous solution of NaCl, an immiscible organic solvent is added. The two solvents are shaken sufficiently to ensure mass transfer from the aqueous phase to the organic phase. The organic impurities (compounds) are transferred from the aqueous phase to the organic medium due to their greater solubility in the organic medium. In the solvent extraction process, multi-step extraction is more efficient than single-step extraction.

2. the density of DCM (CH2Cl2) is 1.33 g/cm3, of which water has a density of 1 g/cm3. so it is obvious that DCM is heavier than water. Therefore, the DCM layer is the bottom of the NaHCO3 layer of water. In this experiment, the DCM layer contains organic matter and the NaHCO3 layer contains NaCl.

3. as the temperature increases, the solubility of most compounds increases. Solute molecules are linked together by several intramolecular interactions, and solvent molecules can break down solute molecules more efficiently at high temperatures. The average kinetic energy of solute molecules also increases with increasing temperature, which destabilizes the solid structure. This is the most likely cause dor this tendency.