Glycolic acid structure is one of the smallest molecules in the α-hydroxy acid (AHA) family. Its structure and other properties are illustrated in this article
Glycolic acid structure is a monocarboxylic acid where the methyl group is replaced by the hydroxyl (-OH) group. The glycolic acid structure also has functional group duality of carboxylate group (-COOH) and hydroxyl group (-OH) structure which is responsible for its various physical and chemical properties and applications.
Glycolic acid structure representation
Glycolic acid can be represented in 2D and 3D ways. The 2D structure is represented by a lines and wedges model. It shows that glycolic acid structure comprises 8 bonds in total where there are 4 non-hydrogen bonds, one double bond, one aliphatic carboxylic acid group, 2 hydroxyl groups, and 1 rotatable bond.
The chemical formula of glycolic acid is HOCH2COOH and its IUPAC name is 2-hydroxyacetic acid or 2-hydroxyethanoic acid. It can also be designated by other names like α-hydroxy acetic acid, Glycol acid, 2-hydroxy-Acid glycol, etc.
The glycolic acid 3D structure can be visualized with the help of the Ball and stick model or X-ray crystallographic technique. Its crystallography and 3D structure description explain the positioning and orientation of various atoms in the molecule. The 3D glycolic acid structure represents spheres as various atoms in the glycolic acid molecule and the length of the rods as the bonds. In glycolic acid structure length of the bonds are longer and larger than the radius of the atom representing spheres.
Properties explained by Glycolic acid structure
Glycolic acid structure can explain many properties related to its physical appearance or chemical behavior.
Elaborating more about glycolic acid structure properties then it is odorless, colorless, and hygroscopic crystalline solid. Its molar mass is 76.05 g/mol and its density is 1.49 g/cm3. Its melting point is 75 degrees Celsius and it completely decomposes at its boiling point. Glycolic acid is soluble in water with a 70% solubility range. It is also soluble in organic solvents like alcohol, acetone, acetic acid, and ethyl acetate.
Another important property demonstrated by Glycolic acid structure is acidity. Glycolic acid is of slightly stronger acidity as compared to ethanoic acid. The reason behind this increased acidity is the presence of a strong electron-withdrawing hydroxyl group instead of a hydrogen of methyl group as shown by ethanoic acid. The strong electron-withdrawing terminal hydroxyl group attracts the electron which thereby increases the electron density cloud around the molecule and increases the –I (Inductive effect) effect hence increasing the acidity of the whole molecule.
Due to the presence of the carboxylate group glycolic acid structure can form coordinate complexes with various transition metal ions especially Pb2+ and Cu2+. The carboxylate group can easily coordinate with metal ions. The Hydroxyl group also shows involvement in the complex formation due to the loss of hydrogen ions or protons.
Occurrence of Glycolic acid
Glycolic acid is usually found in nature. It is commonly found in vegetables and fruits. But its most common source is sugarcane. Pineapple, unripe grapes, and cantaloupe are other sources from which they can be easily isolated.
Biochemically, it is prepared during photorespiration. But its formation is very tough because photorespiration is a waste side reaction of photosynthesis. The possibility of preparation of glycolic acid naturally though slim is not impossible. It can be extracted using various other enzymatic pathways which require less energy usage.
Applications of Glycolic acid
Glycolic acid has several uses and applications. In the textile industry, it is used for dying fabrics and leather tanning. In the food production, processing, and packaging industry it is used for all the purposes. It is used as a preservative and flavor-enhancing agent. Its various compounds and derivatives are used in solvents, plastics, emulsions, additives of paints and inks, and as floor cleaning agents.
In many laboratory preparations and academic research, it is used as an intermediate for organic synthetic methodologies like long-chain polymerization reaction, esterification, and an oxidation-reduction reaction.
Glycolic acid is a big game-changer in the beauty, skincare, and cosmetic industry. Many beauty experts and cosmetologists swear by glycolic acid in their skincare routines. It is mentioned by several researchers that being the smallest molecule in the α-hydroxy acid (AHA) family it is easily penetrable and absorbable in the skin.
Many glycolic acid peels, serums, soaps, and exfoliators have hoarded the market. It is usually said that it can cure and treat many dermatological conditions like lightening of acne scars, hyperpigmentation, pore cleansing, extreme dryness, etc. But it should be handled with care as it is corrosive. It can become a potential skin irritant if used in excess or its purest form.
Explain laboratory preparation of glycolic acid
Though many methods are available for the preparation of glycolic acid in laboratory conditions but the most commonly used method is when sodium hydroxide (NaOH) reacts with chloroacetic acid (ClCH2COOH) followed by re-acidification. This gives glycolic acid as a major product and sodium chloride (NaCl) as a minor product. Some other uncommon methods for the synthesis of glycolic acid are hydrogenation of oxalic acid and hydrolysis of cyanohydrins made from formaldehyde.
Who discovered Glycolic acid? Explain its history.
Glycolic acid was first time prepared by German chemist Adolph Strecker and Russian chemist Nikolai Nikolaevich Sokolov in 1851. For the very first time, hippuric acid was treated with nitric acid (HNO3) and nitrogen dioxide (NO2) to obtain it. Its name was first coined by French chemist Auguste Laurent in 1848. This is because he thought that glycine might be the amino acid derivative of the hypothetical acid discovered at that time.
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