Glycolic acid cas. Glycolic acid structural formula

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Glycolic acid (hydroxyacetic or hydroxyethanoic acid, Glycolic acid) is an organic compound that is a representative of alpha hydroxy acids (AHAs). The synthetic method of producing glycolic acid provides higher purity, quality and stability than natural sources.

What is glycolic acid used for in cosmetology?

Glycolic acid is effective for treating hyperkeratosis due to its small molecular size. Due to this, as well as hydrophilicity and hygroscopicity, it destabilizes the aqueous phase between the lipid bilayers filling the intercellular spaces of the stratum corneum.

Glycolic acid is used in both professional and home peels. In low concentrations (2-5%) it is found in home care, weakening the adhesion between corneocytes and ensuring uniform exfoliation of the outer layers of the epidermis. It has been shown that at such a concentration in cosmetic products (in particular in these - https://thaishop.com.ua/uk/product-category/oblichchya/) there is no damage to the barrier functions of the skin, and the result is a decrease in the thickness of the stratum corneum.

In professional care, higher concentrations of glycolic acid are used - from 30 to 70% with different pH values. Since the irritating effect of alpha hydroxy acids depends on the pH level, the use of glycolic acid with a pH of at least 2 is allowed in beauty salons. Lower pH values ​​(< 2) и высокие концентрации (50-70%) могут применяться только в medical institutions. Glycolic acid perfectly eliminates, even if the skin has not been cared for for years. However, it should not be prescribed for very dry skin or damaged epidermis.

Always prepare the skin by restoring its protective barrier - this often takes about 3 weeks - and then use glycolic or similar alpha hydroxy acid to help ease corneocyte desquamation.

By the way, the trend from the 90s of mixing glycolic acid with other alpha hydroxy acids (and not only with them) is now returning to fashion. Previously, such mixtures were really popular and received many flattering reviews from cosmetologists and dermatologists. In principle, glycolic acid combines well with many active ingredients - such as lactic and kojic acid, as well as vitamin C.

There is debate about the effectiveness and irritant effects of glycolic acid. Unfortunately, many physicians approach the use of alpha hydroxy acids without proper knowledge of their effects on the cells and systems of the epidermis, as well as without understanding the long-term consequences and the need for pre- and post-care. Usually it is these “specialists” who then write angry reviews about glycolic acid.

Elena Hernandez Marina Kryuchkova

Introduction

First appearing in cosmetics at the beginning 90 's, a-hydroxy acids (alpha hydroxy acids, AHA) have rapidly conquered the cosmetic market. Today these are one of the most popular ingredients in a variety of cosmetic products.

In the material prepared by our editors together with specialists from raw materials companies, consultants from well-known professional cosmetic lines and practicing doctors, we will talk about the biological effects of AHA in the skin, the principles of developing AHA-containing preparations and their use in cosmetological practice.

What's happenedA.H.A.

Organic substances that contain different functional groups are called mixed-function compounds. These compounds also include hydroxy acids, which, along with the acidic (carboxyl) group -COOH, have a hydroxyl (alcohol) group -OH. According to a common version of nomenclature, the carbon atom to which the carboxyl group is attached is designated by the letter a, the next carbon - (3, and so on, in accordance with the Greek alphabet. In the case of sufficiently long chains, the atom farthest from the carboxyl is usually designated co. Accordingly, if the hydroxyl group is located at the a-carbon atom, then such a compound is called an a-hydroxy acid (AHA), at the 3-atom - (3-hydroxy acid (BHA), etc. (Fig. 1).

In nature, the most common are se-hydroxy derivatives of carboxylic acids (AHA). They are obtained from sugar plants, as well as from some biological substances. For example, glycolic acid comes from sugar cane, lactic acid comes from sour milk, tartaric acid comes from old wine, citric acid comes from citrus fruits, and malic acid, as you might guess, comes from apples. Hydroxy acids derived from fruits are often called fruit acids.

nosn 2 coax 2 coon o / : \ o (C 2 H 2 0 2) x

glycolide SOSN 2 polyglycolide

carboxymethylhydroxyacetate

Rice. 2. Compounds obtained by reacting glycolic acid molecules with each other

G lycolic (hydroxyacetic) acid is the first and smallest in the series of hydroxy acids: it contains only two carbon atoms. Like other AHAs, glycolic acid is soluble in highly polar solvents (water, methanol, ethanol, acetone, acetic acid, ethyl acetate), sparingly soluble in ethyl ether and practically insoluble in non-polar hydrophobic saturated hydrocarbons. Glycolic acid molecules, reacting with each other, are able to transform into linear polyester oligomers, cyclic glycolide dimers, linear dimers and polymers (Fig. 2). When combined with other AHAs, glycolic acid can also form biodegradable ester copolymers. The properties of these copolymers (decomposition rate, solubility in water, etc.) are determined by their composition and molecular weight. Microspherical particles are made from copolymers that are poorly soluble in water and are considered promising drug carriers.

Water-soluble forms of AHA are used in dermatological and cosmetic preparations, in which they affect the condition of the skin at the molecular, cellular and tissue levels.

Biological effectsA.H.A.

The first mention of the cutaneous use of glycolic acid dates back to 1974. Van Scoth And Yu, while studying the effect of various drugs for ichthyosis, they found that glycolic acid is able to control the process of keratinization of the epidermis, weakening the adhesion between corneocytes. Similar effects have been found in other AHAs. Subsequently, the therapeutic effectiveness of AHA was established for all forms of hyperkeratosis. Further studies showed that AHAs easily penetrate the stratum corneum, reach the lower layers of the epidermis, and even pass through the basement membrane into the dermis (Figure 3).

Exfoliating effect

One of the main effects of AHAs - exfoliation - is associated with their ability to weaken the cohesion of corneocytes. AHAs do not cause disaggregation of corneocytes in the upper layers of the stratum corneum, but affect the cohesion of corneocytes in its lower, younger layers (Fig. 3). This is how they fundamentally differ from true keratolytic agents - strong acids, alkalis, thiols and denaturing substances such as urea and lithium salts in high concentrations.

The thickness of the stratum corneum in health and disease is determined by two opposing factors - those that weaken the cohesion of corneocytes and those that strengthen it. Both covalent (for example, disulfide, peptide and intersaccharide) and various non-covalent (including ionic) bonds take part in corneocyte cohesion. The most common non-covalent bond that does not have a pronounced ionic character is a hydrogen bond. It is very weak and is easily destroyed by agents such as lithium bromide, urea and alkalis, which act as chemical denaturants (chaotropic, i.e. disordering reagents). Intermolecular hydrogen bonding is also weakened when diluted with water due to competition between the solute molecules and the water molecules themselves, which are very prone to hydrogen bonding. Ionic bonds occur between oppositely charged groups - negative (for example, carboxyl, sulfate, phosphate) and positive (amino groups of basic amino acids).

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Let us remember that the stratum corneum of the epidermis consists of corneocytes (horn cells), between which there is a lipid layer holding them together. This layer is most developed in the middle of the stratum corneum, however, at the level of the transition of the granular layer into the stratum corneum, this layer is still weakly expressed. Here there is still an aqueous phase between the cells, and the cohesion of corneocytes is carried out mainly due to ionic interactions. These interactions are due to the presence on the surface of cells of charged groups of various biomolecules that make up cell membranes - mucopolysaccharides, glycoproteins, sulfur-containing sterols and phospholipids (Fig. 4).

Ionic bonds and, accordingly, cohesion of corneocytes are determined by three main factors:

the distance between cells, in other words, between positive and negative groups on the surface of neighboring cells;

intercellular environment;

charge density, i.e. the number of positive and negative groups per unit surface of the cell walls of corneocytes.

By influencing one or more factors, the adhesion strength of corneocytes can be modulated. Thus, when the stratum corneum is hydrated, the distance between corneocytes and, consequently, between the opposite charges of the cell walls of corneocytes increases, which leads to a decrease in the adhesion force.

As for the distribution and density of various charged groups on the surface of cells, this process is under the control of a number of enzymes. The most “mobile” are sulfate and phosphate groups, which are easily cleaved off by common epidermal enzymes sulfatases and phosphatases. Amino and carboxy groups are more difficult to remove, so their number on the cell surface is more or less constant.

Recently, it was discovered that in X-linked ichthyosis there is a congenital deficiency of sulfatase activity in skin fibroblasts, cultured keratinocytes, throughout the epidermis and in the stratum corneum, as well as in other tissues. Thus, the number of sulfate groups is not sufficiently controlled, and their density on the cell surface increases. As a result, the adhesion force between corneocytes increases, the desquamation process is inhibited and the stratum corneum becomes thicker and denser than normal.

AHAs are effective for any form of hyperkeratosis. It is believed that they affect the activity of some enzymes involved in the formation of ionic bonds. The exact mechanism of this process is not completely clear. Apparently, the effect on enzymes occurs simultaneously in several ways (Fig. 5). For example, it is known that AHAs can replace sulfate and phosphate groups in reactions catalyzed by sulfate transferases, phosphotransferases and kinases. These enzymes are responsible for the sulfation and phosphorylation of mucopolysaccharides, glycoproteins, sterols and phospholipids on the cell surface. Some AHAs are also known to directly inhibit the enzymatic activity of phosphotransferases and kinases. So, lemon acid significantly inhibits glucose-6-phosphotransferase and phosphofructokinase. In addition, AHAs can act as acceptors of phosphate groups to form phosphorylated AHAs.

D For small hydrophilic molecules AHA, the stratum corneum is not an obstacle: they quite easily overcome it and find themselves in the intercellular aqueous environment of the granular layer, where they interact with corneocytes. The smaller the AHA molecule, the better it passes through the stratum corneum. Glycolic acid has the best penetrating ability precisely because of its small size. Unlike hydrophobic retinoids, AHAs do not require special binding receptors on the plasma membranes of cells. The weakening of the adhesion of corneocytes at the level of the granular layer contributes to their faster advancement into the stratum corneum and subsequent rejection (exfoliation). This serves as a signal for the division and differentiation of the underlying keratinocytes. Thus, the life cycle of the main cells of the epidermis - from the basal cell (keratinocyte) to the horny scale (corneocyte) - is shortened. At the same time, the thickness of the stratum corneum decreases, which is determined by the rate of renewal of the epidermis and the rate of desquamation of scales from the surface of the skin.

An imbalance between the processes of exfoliation and cell division of the basal layer in combination with impaired differentiation of keratinocytes underlies a number of pathologies, such as hyperkeratosis (ichthyosis, keratodermin), parakeratosis (psoriasis), dyskeratosis (Darney's disease, Bowen's disease). In aging skin, a decrease in the mitotic activity of cells in the basal layer is usually accompanied by delayed exfoliation, which leads to a thickening of the stratum corneum. In these cases, the use of ANA drugs is completely justified, since their action results in a decrease in the thickness of the stratum corneum and faster renewal of the epidermis.

Influence on the barrier function of the stratum corneum

The question arises: will increased peeling lead to a weakening of the barrier function of the stratum corneum? Fartasch et al. conducted a series of experiments in which, using morphological and biophysical methods, they studied the effect of AHA on the stratum corneum. For three weeks, 4% glycolic acid was applied to the inside of the volunteers' forearm twice a day, and then the treated area was biopsied. Using electron microscopy, we studied: 1) the morphology and thickness of the stratum corneum, 2) lamellar bodies and the organization of lipid layers, and 3) the adhesion of corneocytes. In addition, the transepidermal water loss (TEWL) and the degree of hydration of the stratum corneum were assessed before and after treatment. It turned out that no morphological changes occurred in the nuclear layers of the epidermis: normal lamellar bodies were present in the cells of the granular layer, and the structure of the lipid layer in the stratum corneum did not change after treatment of the skin with glycolic acid. The TEWL indicator, which is used to judge the barrier properties of the stratum corneum, also did not change. These data, along with those of other authors, indicate that AHAs specifically act on corneocyte cohesion without disrupting the stratum corneum barrier.

Moreover, there is evidence that some AHAs have a positive effect on the synthesis of ceramides, the most important components of the intercellular lipid layers of the stratum corneum. By studying the effect of lactic acid isomers on ceramide biosynthesis and the state of the stratum corneum barrier, scientists from the company Unilever found that lactic acid not only increased the total amount of ceramides in the stratum corneum, but also modulated the type of ceramides synthesized in cells. As is known, ceramides play a special role in maintaining the integrity of the stratum corneum 1 . They contain long-chain polyunsaturated fatty acids, mainly linoleic acid (75-80%). They play the role of rivets in the lipid structures of the stratum corneum, penetrating adjacent lipid layers and fastening them to each other. With a deficiency of linoleate-containing ceramides 1, the normal structure of the lipid barrier is disrupted, resulting in increased permeability of the stratum corneum. This occurs with atopic dermatitis, deficiency of essential fatty acids, and acne. In experiments in vivo And in vitro The L-enantiomer (optical isomer) of lactic acid has been shown to stimulate the synthesis of ceramides 1 containing polyunsaturated fatty acid tails. When a culture of human keratinocytes is incubated daily in a medium containing 20 mM lactic acid, the qualitative composition of synthesized lipids changes: in addition to ceramides 2, characteristic of the lipid metabolism of cells in culture, ceramides 1 and 3 appear. Qualitative analysis of ceramides 1 after a month's application of 4% an aqueous solution of L-lactic acid on the forearm of volunteers showed that the ratio of linoleate- and oleate-containing ceramides 1 increases sharply.

The effect depended on which optical isomer of lactic acid was used. In experiments in vitro The L-form was much more effective than the D-form (increasing ceramide synthesis by 300 and 100%, respectively). In experiments in vivo Only the L-isomer was effective. Thus, a lotion with the L-form increased synthesis by 48%, with a DL-form - by 25%, and a lotion based on the D-form had no effect. The effect on the barrier function of the epidermis is evidenced by TEWL measurements on an area of ​​skin previously irritated with sodium lauryl sulfate. Treatment of this area with L-lactic acid accelerated the restoration of the barrier, while the D-form was ineffective.

The effect of AHAs on the biochemistry of epidermal lipids described in the work is one of the few known mechanisms of their action on the state of the epidermis.

Moisturizing effect

A decrease in the cohesion of corneocytes affects another very important parameter that largely determines the appearance of the skin - the hydration of the epidermis. “A significant contribution to the overall hydration of the epidermis is made by water,” which is retained by a complex of hygroscopic molecules called natural moisturizing factor (natural moisturizing factor, NMF). Located in corneocytes, NMF provides elasticity and mechanical strength to the horny scales. NMF is better developed in younger corneocytes. As the corneocytes move toward the noBepxHocnrNMF, the NMF gradually degrades, and the horny scales become drier and more brittle. The rapid sloughing of horny scales and renewal of the epidermis leads to an increase in the content of functionally active NMF in the skin and, consequently, the water associated with it. The best moisturizing effect is characteristic of lactic acid, which, among other things, is directly included in NMF.

Water content is also increased by AHA due to other factors. Thus, hygroscopic AHA molecules are able to bind water and, penetrating the skin, deliver it to the deep layers of the epidermis. In addition, strengthening the barrier function of the epidermis, as well as stimulating the synthesis of glycosaminoglycans (see below) increases the water-saving and water-retaining properties of the skin.

Anti-inflammatory and antioxidant effects“LITA have an anti-inflammatory effect, influencing inflammatory mediators, reducing the production of superoxide and hydroxyl radicals, and participating in the functioning of B and T lymphocytes.

Interesting and, at first glance, somewhat unexpected data on the photoprotective and anti-inflammatory effects of glycolic acid were obtained Perricone And DiNardo. It was decided to test the popular belief that treating the skin with glycolic acid increases the skin's sensitivity to solar radiation, in other words, causes photosensitization of the skin. Two series of experiments were carried out. In the first series, the anti-inflammatory potential of glycolic acid was assessed based on the erythema reaction. Two symmetrical areas on the back of volunteers were irradiated three times with minimum erythemal dose (MED) UV-B. Four hours after irradiation, glycolic acid cream (oil-in-water emulsion, 12% glycolic acid partially neutralized with ammonium hydroxide to pH 4.2) was applied to one area, and placebo cream was applied to the other. The areas were treated with cream 4 times a day. 48 hours after the last application of the cream, the size of the erythema was assessed. There was a significant reduction in erythema in the area treated with glycolic acid cream.

In the second series of experiments, four areas on the backs of volunteers were irradiated:

section I(control) served to establish the MED for a given subject and was not treated with anything after irradiation;

plot2 24 hours after irradiation, the MED began to be treated with two AN A products - a cleansing lotion and an oil-free moisturizing lotion (both contained 8% glycolic acid and had a pH of 3.25); processing was carried out within 7 days;

plot3 for 3 weeks before irradiation, they were treated with the same AHA products as area 2;

plot4 was treated in the same way as area 3, but 15 minutes before irradiation, it was chemically peeled with a 50% glycolic acid solution for 6 minutes.

It turned out that the degree of erythema in area 2, which was treated with AHA products after irradiation, was 16% less than in control area 1. This suggests that when treated with glycolic acid, the skin heals faster. A comparison of sections 1 and 3 showed that pre-treatment of the skin with glycolic acid increases its resistance to radiation by 2.4 times. Chemical peeling of the skin before irradiation (section 4) reduces the sun protection properties of the skin by almost 2 times compared to section 3, however, even in this case, the resistance of the skin to irradiation is 1.7 times higher compared to control section 1. The data obtained indicate that glycolic acid It has a photoprotective effect, increasing the skin's resistance to radiation. In addition, treating irritated skin with glycolic acid leads to a faster disappearance of erythema.

The anti-inflammatory effect of different AHAs is expressed to varying degrees and is directly related to their antioxidant properties. Thus, a comparison of four AHAs - glycolic, lactic and tartaric acids and gluconolactone (an internal ester of gluconic acid) - showed that the latter two compounds, which are also stronger antioxidants, have a more effective anti-inflammatory effect.

However, the antioxidant properties of isolated AHAs are not very strong. However, when AHAs are combined with other antioxidants, a synergistic effect occurs, due to which the overall antioxidant potential of the mixture increases significantly. Moiteae And Livrea studied the antioxidant activity of glycolic acid paired with vitamin E and melatonin on model lipid bilayers and human skin homogenate. They found that in the presence of glycolic acid, the antioxidant activity of vitamin E increases by 2.5 times, and melatonin by 1.8 times. The role of glycolic acid appears to be reduced to the restoration of the second component, as a result of which its antioxidant potential increases.

Strengthening the synthesis of collagen and gpicosaminoglycans

There is still no final clarity regarding how AHAs smooth out fine wrinkles. One aspect of their action is the stimulation of fibroblast proliferation and activation of the synthesis of collagen I, which is part of the intercellular substance of the dermis. In addition, it has been shown that glycolic acid stimulates the biosynthesis of glycosaminoglycans, which are also part of the intercellular substance and are involved in intercellular communication.

The effectiveness of action varies among different AHAs and is directly proportional to their dose. Yes, in experiments in vivo And in vitro It has been shown that among the AHAs, glycolic acid has the strongest proliferative effect, followed by lactic and malic acids.

Under the influence of AHA, the stratum corneum of the epidermis becomes thinner, and the dermis, on the contrary, thickens. As a result, small wrinkles are smoothed out, and large ones become less noticeable. Unfortunately, the amounts of AHAs that our body produces are not enough to prevent the formation of wrinkles. Moreover, a-acetoxy acids are synthesized in the body (alpha acetoxy acids, AAA), which act opposite to AHA: they cause thickening of the epidermis and thinning of the dermis, and also contribute to the development of whiteheads and blackheads.

General approach to the development of AN A-cosmetics

A technologist working on the formulation of a cosmetic product with AHA simultaneously solves several problems. First of all, it should be remembered that AHAs are substances with strong biological effects. With proper use of AHA cosmetics, the effect exceeds all expectations - the appearance of the skin improves significantly, but if used uncontrolled and incorrectly, irreparable damage can be caused to the skin. In the case of AHA cosmetics, the line between safety and effectiveness is very narrow, and the product must be balanced to achieve maximum effectiveness with minimal risk. On the other hand, the developer faces a difficult technological task - to create a product that is stable at low pH values.

ChoiceA.H.A.

AHAs used in cosmetology can contain up to 14 carbon atoms in their molecule. Depending on the molecular weight and structure of the hydrocarbon chain, which can be linear or branched, saturated or unsaturated, contain a different number of carboxyl and hydroxyl groups, and have other active groups (amino, keto, thio groups), a given AHA may be superior to other AHAs or , on the contrary, to yield to them in the manifestation of certain properties.

The biological activity of AHA also depends on the configuration of the molecule. For example, in the case of lactic acid, only the L-isomer is effective, while the D-isomer does not have any pronounced effect on the skin.

Often, not one, but a mixture of several different acids is introduced into the recipe. For example, many AHA products combine glycolic acid with fruit acids. Recently, products containing a mixture have become popular A- and P-hydroxy acid (so-called AHA/BHA products). It is believed that AHAs have a more pronounced exfoliating effect, and BHAs have a stronger proliferative effect.

Among the AHAs approved for use in cosmetics are the following: glycolic, lactic, apple, lemon, tartaric. Among the BHAs, salicylic acid can be called, although from a chemical point of view it is not typical. An American chemical company has been working in this direction for several years now. Inolex, which has developed several options for polyester carriers for various hydrophilic and lipophilic biologically active substances, including AHAs and UV filters. Polyester components with different structures, different molecular weights and solubility are selected taking into account the chemical characteristics of the delivered agent. They have the ability to penetrate the barrier of the stratum corneum without disturbing its structure, and gradually release the active ingredient in the deeper layers of the skin.

Work on creating an effective, controlled delivery system for AHAs into the deep layers of the skin is being carried out not only in scientific centers manufacturing companies, but also in independent laboratories. Recently in International Journal of Pharmacology Interesting results obtained by Italian scientists from the Department of Pharmaceutical Chemistry of the University of Pavia were published. While studying the problem of liposomal delivery of glycolic acid, they selected the optimal parameters of a system that allows glycolic acid to be delivered to the skin effectively and without adverse reactions. They investigated different types of microcapsule carriers: liposomes, chitosan-modified liposomes, and chitosan microspheres. Liposomes consisting of phosphatidylcholine and cholesterol (molar ratio 1:1) were prepared by a standard phase reversal method. Chitosan was added to the lipid bilayer at the stage of preparing liposomes or already prepared liposomes were coated with it. Microcapsules were studied using an electron microscope, and their sizes were monitored by light scattering. Specific dissolution tests have been developed to evaluate the ability of microparticles to modulate glycolic acid release. in vitro. The results showed that liposomes can modulate the release of glycolic acid, and the optimal condition for this is a glycolic acid/lipid molar ratio of 5:1. Liposomes with added chitosan can also gradually release glycolic acid, while chitosan microparticles are not able to control the release of glycolic acid under any conditions.

CombinationA.H.A.with other components

The exfoliating effect of AHA facilitates the penetration of other biologically active substances that may be present in the preparation. Thus, AHA formulations often include antioxidants (for example, vitamins C and E) and plant extracts with various properties

(anti-inflammatory, moisturizing, sedative). Formulations developed for pigmented skin include whitening agents such as hydroquinone or kojic acid. ANA preparations also contain biologically active components such as hyaluronic acid, pyrrolidonecarboxylic acids, squalene, peptides and amino acids, urea, phytoestrogens, the effectiveness of which increases in the presence of AHA.

Emollients are mandatory components in ANA-preparations. Without exerting any biological effect, emollients nevertheless perform a very important function - they temporarily soften and protect the surface of the skin that has undergone peeling. Among the emollients included in AHA preparations, both natural and synthetic compounds are used.

Conclusion

After treatment with AHA preparations, the skin becomes firmer and more elastic, the number of small spots and the severity of deep wrinkles- the skin is smoothed and looks younger and fresher. Miraculous skin rejuvenation is associated with the diverse biological effects of AHA. Thus, in the epidermis, AHAs activate the process of exfoliation of dead cells and increase the degree of hydration. As part of the dermis, AHAs influence the synthesis of the main elements of the intercellular matrix - collagen and glycosaminoglycans. The anti-inflammatory effect of AHAs is due to their antioxidant properties and ability to influence inflammatory mediators. Although many aspects of the mechanism of action of AHAs are not fully understood, the overall picture is clear. It is the versatility of the action of AHA that determines wonderful effect which is observed after a course of ANA therapy.

In the second part of our review, located in the “Medicine” section, we will talk about the use of AHA in clinical practice and consider various options, in which the use of AHA is effective and justified.

Name Glycolic acid Synonyms hydroxyacetic acid; CAS registration number 79-14-1 Molecular formula C 2 H 4 O 3 Molecular weight 76.05 InChI InChI=1S/C2H4O3/c3-1-2(4)5/h3H,1H2,(H,4,5) InChIKey AEMRFAOFKBGASW- UHFFFAOYSA-N SMILES C(C(=O)O)O EINECS 201-180-5

Chemical and physical properties

Density 1.27 Boiling point 113°C Melting point 10°C Flash point 128.7°C Refractive index n20/D 1.424 Solubility H2O: 0.1 g/ml. Stability Stable. Incompatible with bases, oxidizing agents and reducing agents. Appearance Light yellow or dark red liquid.

Risks, safety and terms of use

Safety instructions S26; S36/37/39; S45 Risk statements R22; R34 Hazard class 8 Hazard symbols

Classification of chemical reagents

Pure (“pure grade”) Glycolic acid Purpose grade. The content of the main component is 98% or higher (without impurities). The color of the stripe on the packaging is green. Pure for analysis (“analytical grade”, “analytical grade”) Glycolic acid, analytical grade. The content of the main component is higher or significantly higher than 98%. Impurities do not exceed acceptable limits for accurate analytical studies. The color of the stripe on the packaging is blue. Chemically pure (“reagent grade”, “chemically pure”) Glycolic acid, chemically pure. The content of the main component is more than 99%. The color of the stripe on the packaging is red. Extra pure (“special purity”) Glycolic acid, special purity grade. The content of impurities is in such small quantities that they do not affect the basic properties. The color of the stripe on the packaging is yellow.

Glycolic acid (hydroxyacetic acid, hydroxyethanoic acid) is an organic compound with the chemical formula C 2 H 4 O 3, the simplest hydroxy acid. Colorless crystals with the smell of burnt sugar.

Application

Glycolic acid is used in various fields:

• in organic synthesis
• in industry - equipment cleaning
• when processing metals (in particular, pickling)
• in the leather industry
• in the oil and gas industry
• in economic activities - as part of cleaning products
• in cosmetology: as a keratolytic in chemical peeling of the skin, in the treatment of hyperkeratosis
• as a natural exfoliant, cleanses sebaceous ducts from comedones (blackheads), promotes the penetration of other active substances into the skin,
• in the production of absorbable suture materials for surgical operations: dexon and polyglactin-910.

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Literature

• O. Y. Neyland. Organic chemistry. - M.: Higher School, 1990. - 751 p. - 35,000 copies. - ISBN 5-06-001471-1.

Excerpt describing Glycolic acid