Glycolic acid

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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):
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).

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.

References

  1. https://www.degruyter.com/view/books/9783110434330/9783110434330-011/9783110434330-011.xml

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