Glycolic acid
| Names | |
|---|---|
| IUPAC name
2-Hydroxyethanoic acid
| |
| Other names
Dicarbonous acid
Glycolic acid Hydroacetic acid Hydroxyacetic acid Hydroxyethanoic acid | |
| Properties | |
| C2H4O3 HOCH2COOH | |
| Molar mass | 76.05 g/mol |
| Appearance | White colorless solid |
| Odor | Odorless |
| Density | 1.49 g/cm3 (25 °C) |
| Melting point | 75 °C (167 °F; 348 K) |
| Boiling point | Decomposes |
| 60 g/100 ml | |
| Solubility | Soluble in acetone, acetic acid, diethyl ether, ethanol, ethyl acetate, isopropanol, methanol |
| Vapor pressure | 2·10-2 mmHg at 25 °C |
| Acidity (pKa) | 3.83 |
| Hazards | |
| Safety data sheet | Sigma-Aldrich |
| Flash point | 129 °C (264 °F; 402 K) |
| Lethal dose or concentration (LD, LC): | |
| LD50 (Median dose)
|
2,040 mg/kg (rat, oral) |
| Related compounds | |
| Related compounds
|
Acetic acid Lactic acid |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Glycolic acid (C2H4O3 or HOCH2COOH), also called hydroacetic acid or hydroxyacetic acid, is an organic chemical compound, the smallest α-hydroxy acid (AHA).
Contents
Properties
Chemical
Glycolic acid reacts with hydrogen halides, such as hydrogen chloride, to give their respective monohaloacetic acid, in this case chloroacetic acid.
Glycolic acid is slightly stronger than acetic acid due to the electron-withdrawing power of the terminal hydroxyl group. The carboxylate group can coordinate to metal ions forming coordination complexes. Of particular note are the complexes with Pb2+ and Cu2+ which are significantly stronger than complexes with other carboxylic acids. This indicates that the hydroxyl group is involved in complex formation, possibly with the loss of its proton.[1]
Physical
Glycolic acid is a colorless solid, very soluble in water. It is odorless.
Availability
Glycolic acid is commonly found in many skin-care products.
Original Pine-Sol Multi-Surface Cleaner contains glycolic acid.
Pure glycolic acid can be bought from chemical suppliers.
Preparation
Glycolic acid is often prepared by the reaction of chloroacetic acid with sodium hydroxide, followed by re-acidification.
- Cl-CH2COOH + 2 NaOH → OH-CH2COONa + NaCl + H2O
- OH-CH2COONa + HCl → OH-CH2COOH + NaCl
Glycolic acid was historically first prepared by treating hippuric acid with nitric acid and nitrogen dioxide. This forms and ester of benzoic acid and glycolic acid, which is hydrolyzed to glycolic acid by boiling it in sulfuric acid.
Hydrogenation of oxalic acid is another route.
Glycolic acid can be isolated from natural sources, such as sugarcane, sugar beets, pineapple, cantaloupe and unripe grapes.
Projects
- Make skin exfoliant
- Make polyglycolic acid
- Make monohaloacetic acids
Handling
Safety
Glycolic acid is a strong irritant depending on pH. Like ethylene glycol, it is metabolized to oxalic acid, which could make it dangerous if ingested. However, glycolic acid is relative harmless on skin contact in diluted form, and it's even used in skin-care products.
Storage
Glycolic acid is best kept in plastic or glass bottles.
Disposal
No special disposal is required. Can be poured down the drain.
