Differences between lactic acid and glycolic acid
Lactic acid and glycolic acid, both are organic carboxylic acids, but their structures, properties and uses are really different.

First look at its structure. The chemical formula of lactic acid is\ (C_3H_6O_3\), and its molecule contains one hydroxy and one carboxyl groups. Due to the chiral center of the molecule, there are optical isomers. The chemical formula of glycolic acid is\ (C_2H_4O_3\), and the molecule contains only one hydroxy and one carboxyl groups. The structure is relatively simple to lactic acid, and there is no chiral center.

Second observation of physical properties. Lactic acid is a colorless to light yellow viscous liquid at room temperature, with hygroscopicity and good miscibility with water and ethanol. Its melting point is about\ (18 ^ {\ circ} C\), and its boiling point is about\ (122 ^ {\ circ} C\) (\ (2kPa\)). Glycolic acid is a white crystalline solid with a melting point of about\ (78 - 80 ^ {\ circ} C\). It is also hygroscopic and easily soluble in water, ethanol and ether. In contrast, glycolic acid is a solid at room temperature due to its simple structure and different intermolecular forces, which is different from liquid lactic acid.

Re-discussion of chemical properties. Both have carboxyl groups and are acidic. They can react with bases to form salts and esterification reactions with alcohols. However, the hydroxyl groups of lactic acid are affected by adjacent carboxyl groups and have unique reactivity. For example, intramolecular dehydration can occur under appropriate conditions to form cyclic esters. Glycolic acid is different from lactic acid in some scenarios due to its simple structure and reactivity. Its carboxyl and hydroxyl groups are close to each other, and their mutual influence is different from lactic acid.

In terms of uses, lactic acid is often used as a sour agent, preservative and preservative in the food industry. Because of its mild sour taste and antibacterial properties, it can increase the flavor and shelf life of food. In the field of medicine, lactic acid polymers can be used as biodegradable materials to make sutures and drug sustained-release carriers. Because of their biocompatibility and degradability. Glycolic acid is often used as a chemical exfoliant in the cosmetic industry, which can exfoliate the skin, improve skin texture, and make the skin smooth and delicate. In industry, it can be used to prepare chemical products such as ethylene glycol.

To sum up, although both lactic acid and glycolic acid contain hydroxyl and carboxyl groups, their structural differences lead to different physical and chemical properties, and then their uses are also different. It is of great significance to distinguish the difference between the two in the chemical, pharmaceutical, food and cosmetic industries.