Thioglycolic acid is a colorless liquid that has an unpleasant odor. The formula of this substance is HSCH2COOH. Acid is often 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 a variety of functional groups, it has good solubility in various polar, weakly polar and non-polar solvents. These include water, various alcohols and organic solvents such as chloroform and benzene. With all these substances, the acid is able to mix in any ratio. Thioglycolic acid is not able to dissolve in aliphatic hydrocarbons, such as 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 concentration of the acid be no more than 70%, and the temperature be about 20 degrees Celsius. In case of failureunder these conditions, thioglycolic acid undergoes a self-esterification process.
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 basic compounds, which lead to the formation of various s alts. When interacting with alcohols as a result of the esterification reaction, esters will be formed. It is also possible to obtain various amides, sulfides, thiolates. You can carry out reactions to replace the functional group, or add new ones. Under the action of a strong oxidizing agent, the thiol group is affected, resulting in the formation of sulphoacetic acid (HSO3CH2COOH).
In alkaline solutions, acid can oxidize. This reaction requires catalysts, which can be s alts of copper, manganese or iron. As a result of acid oxidation, dithiodiglycolic acid is formed, the formula of which is (HOOCCCH2S)2.
Using thioglycolic acid
This compound is widely used in hair curling and coloring. In a rich assortment of preparations that are used for perm, either thioglycolic acid itself or its derivative compounds, such as s alts, are used. This acid, due to its substituents, has good reducing properties. It is the compounds with thiolfunctional groups can act on the hair structure at a normal temperature for a person, that is, at about 36.6 degrees Celsius. The formation of a new hair structure occurs due to the interaction of thioglycolic acid derivatives with a sulfide bridge in the amino acid (cystine), which is included in keratin, which is the basis of the hair. Therefore, derivatives of this acid are so widely used in this area.
But there are also downsides to using thioglycolic acid for curling. For example, as a result of such an interaction, a large amount of hydrosulfide acid (H2S) and mercaptans are released. It is because of these substances that a sharp and unpleasant odor appears. Also, these substances are toxic to humans. They can cause severe headache, weakness, feeling unwell, 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 dilute solutions have a less obvious such effect. S alts of thioglycolic acid 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, after contact, damage to the skin and mucous membranes occurs, and compounds that, when burned, emit toxic and dangeroussubstances.
Thioglycolic acid is a highly toxic compound. When conducting experiments on rats, LD50 was determined, which is only 50 mg per 1 kg of body weight.
Precautions
Especial attention to precautions should be given to hairdressers, as they often work with thioglycolic acid. Use dilute solutions with a pH close to neutral, i.e. around 7. Also, wear gloves to protect your hands from damage that acid can cause.
Do not use products containing thioglycolic acid if there are any skin lesions, it may cause more extensive damage.
Thus, hairdressers and people who often perm their hair should pay special attention to this substance, as precautions must be taken to maintain their he alth.
