The Extraction of Benzoic Acid
Introduction Extraction is a purification technique used in organic chemistry to separate compounds from a mixture of two or more compounds. There are three different extraction techniques: liquid-liquid extraction, solid-liquid extraction and chemically active extraction. All three types of extraction follow the same principle. Organic molecules dissolve in organic solvents and polar molecules dissolve in aqueous solvents. This phenomenon is observed because of the intermolecular forces between solvent and solute molecules. For example, in aqueous solvents, the polar solute can interact with the solvent via hydrogen bonding, electrostatic forces, ion dipole forces, dipole-dipole forces and London forces. All of these can help a polar solute dissolve in an aqueous solvent. Polar molecules can be involved in these interactions because they have a partial charge. This partial charge is brought upon by the differences in electronegativity between the atoms in the molecule. The difference in electronegativity created a dipole in the molecule. The partially positive hydrogen atoms in H2O molecules are then able to interact with the partially negative part of the molecule and the partially negative oxygen atom in the H2O molecule is able to interact with the partially positive parts of the molecule. The exception is London forces, which is an interaction that nonpolar molecules can participate in as well due to the transient dipole moments that exist in them. In the solid-liquid extraction, a solvent is added to a mixture of solid compounds. A specific compound in the mixture will dissolve in that solvent. Vacuum filtration can then be used to separate the specific compound from the other compounds in the mixture, which are insoluble in that solvent. In the liquid – liquid extraction, you must have solvents that are immiscible (organic and aqueous). The solvents do not mix and separate to form two layers. The solvent with the lower density is on the top and the