This lab serves several purposes. Firstly, the experiment introduces the technique
of extraction, or more specifically, the technique of chemically active extraction, and
demonstrates how to use this method to separate an organic compound (benzoic acid)
from a mixture. Aside from learning this commonly used technique, the lab illustrates
how to separate molecules using an extraction scheme. Lastly, the product collected from
this lab allows for the calculation of the percent yield of benzoic acid.
Theory – Reactions – Mechanisms:
The theory behind this lab explains a number of concepts. The main focus lies in
the following: the use of a chemically active extraction, the relationship between polarity,
solubility, and the distribution coefficient, and the purpose of the extraction scheme.
In general, extractions can involve matter in the liquid, gas, and solid phases.
Nevertheless, liquid-liquid extractions (the main type of extraction used in organic
chemistry) and solid-liquid extractions (an example of which includes making coffee) are
the most common. Oftentimes, the separation of a compound from a mixture is based on
polarity differences between that compound and the other components of the mixture.
Therefore, usually a chemical reaction is needed to alter the polarity of one of the
components of the mixture. Separation by way of adjusting the polarity is known as
chemically active extraction.
Thus, the polarity of molecules plays a great role in extraction, and can also be
related to the solubility of molecules as well as the distribution coefficient of a reaction.
Firstly, it is important to note that organic compounds are mostly non-polar, contain
covalent bonds, and are neutral while inorganic compounds are mostly polar, contain
ionic bonds, and are charged. As a general rule, the solubility of compounds can be
described by their polarities. For example, polar solvents dissolve polar compounds
whereas nonpolar solvents dissolve nonpolar compounds. For the purposes of this class,
the polar solvent is water and the nonpolar solvent is always organic. These two entities
are important because they serve to define the distribution coefficient (K