Glacial acetic acid is a concentrated form of acetic acid, which is an organic compound with the chemical formula CH3COOH. Glacial acetic acid contains less than 1% water and has a purity of about 99.5%. It is called glacial because it freezes into solid crystals at 16.7 °C, slightly below room temperature.
Structure of Glacial Acetic Acid
Glacial acetic acid has the same molecular structure as acetic acid, which consists of two carbon atoms, four hydrogen atoms and two oxygen atoms. The carbon atoms are bonded to each other by a single bond, forming a carboxyl group (COOH) at one end and a methyl group (CH3) at the other end. The oxygen atoms are double-bonded to the carbon atom in the carboxyl group, and the hydrogen atoms are single-bonded to the carbon atoms or the oxygen atom in the carboxyl group.
The molecular geometry of glacial acetic acid is trigonal planar, meaning that the three atoms attached to the central carbon atom lie on the same plane. The bond angle between the oxygen-carbon-oxygen atoms is 120 degrees, and the bond angle between the carbon-carbon-hydrogen atoms is 109.5 degrees. The molecular weight of glacial acetic acid is 60.05 g/mol.
Properties of Glacial Acetic Acid
Glacial acetic acid is a colorless liquid with a pungent odor and a sour taste. It is completely soluble in water and other polar solvents, such as ethanol and acetone. It is also miscible with non-polar solvents, such as benzene and hexane. Glacial acetic acid is a weak acid, meaning that it partially dissociates into hydrogen ions (H+) and acetate ions (CH3COO-) in aqueous solution. The dissociation constant (Ka) of glacial acetic acid is 1.8 x 10^-5 at 25 °C, and the pH of a 1 M solution is 2.4.
Glacial acetic acid is a versatile chemical that has many applications in various industries. It is used as a solvent for recrystallization, purification and extraction of organic compounds. It is also used as a reagent for synthesis of other organic compounds, such as acetic anhydride, cellulose acetate and polyvinyl acetate. Glacial acetic acid is also used as a food additive (E260), where it acts as a preservative, flavoring agent and acidity regulator. In addition, glacial acetic acid is used as a vinegar in cooking and as a household cleaner.
The following table summarizes some of the physical and chemical properties of glacial acetic acid:
| Property | Value |
|---|---|
| Boiling point | 118 °C |
| Melting point | 16.7 °C |
| Density | 1.049 g/mL |
| Viscosity | 1.22 mPa·s |
| Refractive index | 1.371 |
| Flash point | 43 °C |
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