Thioglycolic acid

From Sciencemadness Wiki
Revision as of 18:52, 22 May 2019 by Mabus (Talk | contribs)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search
Thioglycolic acid
Names
IUPAC name
Sulfanylacetic acid
Other names
2-Mercaptoacetic acid
2-Sulfanylacetic acid
Acetyl mercaptan
Mercaptoacetic acid
Thioglycolic acid
Thiovanic acid
Properties
C2H4O2S
HSCH2COOH
Molar mass 92.11 g/mol
Appearance Colorless liquid
Odor Unpleasant, sulfurous
Density 1.3253 g/cm3 (20 °C)[1]
Melting point −16 °C (3 °F; 257 K)
Boiling point 96 °C (205 °F; 369 K) (at 5 mmHg)
Miscible
Solubility Reacts with amines
Miscible with acetone, benzene, chloroform, diethyl ether, ethanol, formic acid, isopropanol, toluene
Immiscible with aliphatic hydrocarbons
Vapor pressure 10 mmHg (17.8 °C)
Acidity (pKa) 3.83
Thermochemistry
Hazards
Safety data sheet Sigma-Aldrich
Lethal dose or concentration (LD, LC):
261 mg/kg (rat, oral)
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

Thioglycolic acid (TGA) or mercaptoacetic acid (MAA) is an organic compound, carboxylic acid with a thiol group. It has the chemical formula C2H4O2S or HSCH2COOH.

Properties

Chemical

Thioglycolic acid is about 100 times stronger acid than acetic acid, with a pKa of 3.83.

Thioglycolic acid is a reducing agent, especially at higher pH.

Thioglycolic acid, usually as its dianion, forms complexes with metal ions. Such complexes have been used for the detection of iron, molybdenum, silver and tin.

Physical

Thioglycolic acid is a colorless liquid, with an unpleasant odor.

Availability

Thioglycolic acid and its esters are commonly used in hair removing products.

Some rust removers or car tar removers contain 5-10% sodium thioglycolate. To obtain the free acid, simply add a weak acid to the salt and purify the reaction product.

Thioglycolic acid is sold by chemical suppliers.

Preparation

Thioglycolic acid is prepared by reaction of sodium or potassium chloracetate with alkali metal hydrosulfide in aqueous medium.

It can be also prepared via the Bunte salt obtained by reaction of sodium thiosulfate with chloroacetic acid.

Projects

  • Chemical depilation
  • Hair permanent
  • Make ammonium thioglycolate
  • PVC stabilizer
  • Make thioglycolate broth

Handling

Safety

Thioglycolic acid is harmful and its strong unpleasant odor may cause health problems.

Storage

Thioglycolic acid should be kept in dark amber bottles, which must be airtight, as the compounds oxidizes in air over time. It is known to oxidize faster in the presence of water.

Disposal

Should be neutralized with hydrogen peroxide or bleach to a less smelly form, then poured down the drain.

References

  1. Klason; Carlson; Chemische Berichte; vol. 39; (1906); p. 739

Relevant Sciencemadness threads