Thioglycolic acid is a colorless liquid that has an unpleasant odor. The formula for this substance is HSCH 2 COOH. Often acid is used to curl hair. But what harm can it bring to the human body? What properties does it have, and where else is it used?
Solubility
Due to the fact that thioglycolic acid has various functional groups, it has good solubility in various polar, slightly polar and non-polar solvents. These include water, various alcohols and organic solvents, such as chloroform and benzene. Acid can be mixed with all these substances in any proportions. Thioglycolic acid is not able to dissolve in aliphatic hydrocarbons, for example, in hexane.
The stability of an aqueous acid solution depends on two factors: concentration and temperature. In order for the solution to remain stable, it is necessary that the acid concentration is not more than 70%, and the temperature is about 20 degrees Celsius. If these conditions are not met, thioglycolic acid undergoes a process of self-esterification.
Chemical properties
Since this acid is a carboxylic acid with a thiol functional group, it is able to enter into all reactions characteristic of carboxylic acids and thiols. These include interaction with the main compounds, which lead to the formation of various salts. When reacted with alcohols, esters will form as a result of the esterification reaction. It is also possible to obtain various amides, sulfides, thiolates. You can carry out reactions to replace a functional group, or add new ones. Under the action of a strong oxidizing agent, an effect on the thiol group occurs, resulting in the formation of sulfoacetic acid (HSO 3 CH 2 COOH).
In alkaline solutions, the acid is able to oxidize. To carry out this reaction, catalysts are necessary, which can be salts of copper, manganese or iron. As a result of acid oxidation, dithiodiglycolic acid is formed, the formula of which is (HOOCCCH 2 S) 2 .
Thioglycolic acid
This compound is widely used for curling and dyeing hair. In a wide range of preparations that are used for perm, either thioglycolic acid itself or its derivatives, for example, salts, are used. This acid, thanks to its substituents, has good reducing properties. It is compounds with thiol functional groups that can act on the structure of the hair under normal temperature conditions for humans, that is, at about 36.6 degrees Celsius. The formation of a new hair structure occurs due to the interaction of derivatives of thioglycolic acid with a sulfide bridge in the amino acid (cystine), which is included in keratin, which is the basis of hair. Therefore, derivatives of this acid are so widely used in this field.
But there are also negative aspects of using thioglycolic acid for curling. For example, as a result of this interaction, a large amount of hydrogen sulfide acid (H 2 S) and mercaptans are released. It is because of these substances that a sharp and unpleasant smell appears. Also, these substances are toxic to humans. They can cause severe headache, weakness, poor health, etc.
Harm
The use of concentrated thioglycolic acid has a strong irritating effect on human skin. In addition, there is irritation of the mucous membranes of the eyes and nose. It is noted that diluted solutions have a less pronounced similar effect. Thioglycolic acid salts can cause various skin lesions, including eczema. Thioglycolates, in turn, cause dermatitis.
The hazard class of thioglycolic acid, according to the UN, is 8. This class includes substances with which damage occurs to the skin and mucous membranes after contact, and compounds that release toxic and dangerous substances when burned.
Thioglycolic acid is a very toxic compound. When conducting experiments on rats, LD 50 was determined, which is only 50 mg per 1 kg of body weight.
Precautionary measures
Special attention should be paid to hairdressers, as they often work with thioglycolic acid. It is necessary to use dilute solutions, the pH of which would be close to neutral, that is, about 7. Also, it is necessary to work with gloves to protect the skin of the hands from damage that acid can cause.
You can not use products that contain thioglycolic acid, if there are any skin lesions, this can lead to more extensive damage.
Thus, special attention should be paid to this substance for hairdressers and people who often permed hair, since precautionary measures must be taken to maintain their health.