Lactic acid
| Names | |
|---|---|
| IUPAC name
2-Hydroxypropanoic acid
| |
| Other names
Milk acid
| |
| Properties | |
| C3H6O3 CH3CH(OH)COOH | |
| Molar mass | 90.078 g/mol |
| Appearance | Colorless liquid or solid |
| Odor | Faint, milk-like |
| Density | 1.206 g/cm3 (20 °C) |
| Melting point | 16.8 °C (62.2 °F; 289.9 K) |
| Boiling point | 122 °C (252 °F; 395 K) (at 15 mm Hg) |
| Very soluble | |
| Solubility | Soluble in diethyl ether, ethanol, furfural, glycerol, methanol, propylene glycol Insoluble in benzene, carbon disulfide, chloroform, petroleum ether |
| Vapor pressure | 0.0813 mmHg at 25 °C |
| Acidity (pKa) | 3.83 |
| Thermochemistry | |
| Hazards | |
| Safety data sheet | Sigma-Aldrich (DL) Sigma-Aldrich (L-(+)) Sigma-Aldrich (D-(-)) |
| Flash point | 110 °C (235 °F; 383 K) |
| Related compounds | |
| Related compounds
|
Glycolic acid |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Lactic acid is an organic acid with the formula CH3CH(OH)COOH. Lactic acid is an alpha-hydroxy acid (AHA) due to the presence of carboxyl group adjacent to the hydroxyl group.
Lactic acid is chiral, consisting of two enantiomers. One is known as L-(+)-lactic acid or (S)-lactic acid and the other, its mirror image, is D-(−)-lactic acid or (R)-lactic acid. A mixture of the two in equal amounts is called DL-lactic acid, or racemic lactic acid.
Contents
Properties
Chemical
In solution, it can ionize a proton from the carboxyl group, producing the lactate ion CH
3CH(OH)CO−
2. Compared to acetic acid, its pKa is almost 1 unit less, meaning lactic acid is ten times more acidic than acetic acid. This higher acidity is the consequence of the intramolecular hydrogen bonding between the α-hydroxyl and the carboxylate group.
Physical
Lactic acid is a colorless solid or liquid, extremely soluble in water. Its solubility is so high that 1 part of lactic acid can dissolve 12 parts of water. It has a faint milk-like odor, often described as acrid.
Availability
Lactic acid is sold by many food and cosmetic suppliers, most often than not as 80% or 60% aq. solution.
Solid lactic acid is sold by chemical suppliers, though the solution form is more readily available.
Preparation
Lactic acid is produced industrially by bacterial fermentation of glucose, lactose or sucrose.
Reduction of pyruvic acid will yield racemic lactic acid.
Projects
- Make pyruvic acid
- Make copper lactate
- Make polylactic acid
Handling
Safety
Lactic acid has low toxicity.
Storage
In closed bottles.
Disposal
No special disposal is required. Can be poured down the drain.
