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CAS Number: 68-11-1
EC Number: 200-677-4
Molecular Formula: C₂H₄O₂S
Molecular Weight: 92.12 g/mol
IUPAC Name: 2-Sulfanylacetic acid
Synonyms:
Thioglycolic acid; TGA; Mercaptoacetic acid; 2-Mercaptoacetic acid; Thiovanic acid; Acetyl mercaptan; Sulfanylacetic acid; α-Mercaptoacetic acid
Chemical Identity and Properties:
Thioglycolic acid (TGA) is an organosulfur compound containing both a carboxylic acid group (-COOH) and a thiol group (-SH). It is a colorless to pale yellow liquid with a strong, sharp, pungent, and unpleasant odor characteristic of thiols. The compound is highly soluble in water and miscible with ethanol, diethyl ether, and most organic solvents. It is hygroscopic and undergoes gradual oxidation in air, with the oxidation accelerated by trace metals such as copper, iron, and manganese .
Physical Properties:
Appearance: Colorless to pale yellow transparent liquid
Melting Point: -16 °C (lit.)
Boiling Point: 96 °C at 5 mmHg; 225.5 °C at 760 mmHg
Density: 1.326 g/mL at 20 °C (lit.)
Vapor Density: 3.2 (air = 1)
Vapor Pressure: 0.4 mmHg at 25 °C
Refractive Index: n20/D 1.505 (lit.)
Autoignition Temperature: 662 °F (350 °C)
Flash Point: 130 °C (closed cup)
pKa: 3.72 (for carboxylic acid); 10.3 (for thiol group)
Solubility: Miscible with water, ethanol, diethyl ether; soluble in organic solvents
Chemical Reactivity and Stability:
Thioglycolic acid is characterized by the reactivity of its thiol group:
Oxidation: Rapidly oxidizes in air to form dithiodiglycolic acid (HOOC-CH₂-S-S-CH₂-COOH). The oxidation is catalyzed by trace amounts of copper, iron, and manganese ions .
Thiol Reactions: Participates in thiol-disulfide exchange reactions; forms thioesters with carboxylic acids; reacts with aldehydes and ketones to form thioacetals and mercaptals.
Salt Formation: Forms water-soluble salts with bases (sodium thioglycolate, ammonium thioglycolate) which are widely used in cosmetic formulations.
Manufacturing Process:
Thioglycolic acid is produced industrially by the reaction of sodium chloracetate with sodium hydrosulfide or sodium polysulfide, followed by acidification. The reaction proceeds through the formation of sodium thioglycolate, which is then treated with mineral acid to liberate the free acid. Alternatively, it can be produced by the reaction of chloracetic acid with thiourea followed by hydrolysis.
Stability and Storage:
Storage Temperature: 2-8 °C recommended for long-term stability
Stability: Stable under recommended storage conditions; degrades upon prolonged exposure to air and light
Incompatibilities: Strong oxidizing agents, strong bases, reducing agents, metals (especially copper, iron, manganese)
Decomposition: Upon thermal decomposition, releases toxic sulfur oxides and hydrogen sulfide gas
Applications:
1. Cosmetics and Personal Care:
Thioglycolic acid and its salts (ammonium thioglycolate, sodium thioglycolate) are the primary active ingredients in:
Permanent waving solutions: Reduces disulfide bonds in hair keratin, allowing hair to be reshaped and then reoxidized to set the new shape
Depilatories: Hair removal creams and lotions; breaks disulfide bonds in hair proteins, causing hair to dissolve at the skin surface
2. Chemical Industry:
PVC Heat Stabilizers: Used in the production of organotin stabilizers for polyvinyl chloride (PVC)
Polymerization Agent: Functions as a chain transfer agent in radical polymerization reactions to control molecular weight
3. Analytical Chemistry:
Reagent for Iron: Used as a colorimetric reagent for the detection and determination of iron (forms a violet complex)
Complexing Agent: Chelates metal ions including iron, molybdenum, silver, and tin
4. Nanomaterial Synthesis:
Quantum Dots: Serves as a capping agent and stabilizer in the synthesis of CdTe quantum dots with controllable photoluminescence wavelengths
Metal Sulfide Nanocrystals: Acts as both a sulfur source and stabilizing agent for hydrothermal synthesis of nanocrystalline metal sulfides; controls morphology and particle size during the process
5. Organic Synthesis:
Thiazolidinone Synthesis: Reactant in one-pot cyclo-condensation reactions with aldehydes and amines to prepare 2,3-disubstituted-thiazolidin-4-one derivatives
Sulfur Source: Used in various organic transformations requiring thiol functionality
6. Industrial Applications:
Mining: Agglomeration suppressant for sulfurized mineral pyrite
Leather Processing: Used in unhairing and tanning processes
Metal Treatment: Corrosion inhibitor and metal cleaning formulations
Safety and Hazard Profile:
GHS Classification:
Signal Word: Danger
Pictograms: GHS05 (Corrosive), GHS06 (Skull and Crossbones)
Hazard Statements:
H301 + H311 + H331: Toxic if swallowed, in contact with skin, or if inhaled
H314: Causes severe skin burns and eye damage
H317: May cause an allergic skin reaction
H400: Very toxic to aquatic life
Hazard Classifications (Sigma-Aldrich):
Acute Toxicity Category 3 (Oral, Dermal, Inhalation)
Skin Corrosion Category 1B
Eye Damage Category 1
Skin Sensitization Category 1B
Aquatic Chronic Category 3
SAFETY INFORMATION ABOUT THIOGLYCOLIC ACID TGA 99%
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
