Salicylic acid is a type of beta-hydroxy acid (BHA) derived from the bark of the willow tree or synthesized in a laboratory. It treats acne by exfoliating the skin, unclogging pores, and reducing inflammation. It’s a widely used ingredient in skincare products, helping to reveal smoother, clearer skin.
| IUPAC Name | 2-Hydroxybenzoic acid |
| Molecular Formula | C₇H₆O₃ |
| CAS Number | 69-72-7 |
| Synonyms | o-Hydroxybenzoic acid; 2-Carboxyphenol, 2-Hydroxybenzoic acid |
| InChI | InChI=1S/C7H6O3/c8-6-4-2-1-3-5(6)7(9)10/h1-4,8H,(H,9,10) |
Salicylic Acid Properties
Salicylic Acid Formula
The formula of salicylic acid is C₇H₆O₃. It consists of seven carbon atoms, six hydrogen atoms, and three oxygen atoms. This chemical formula represents the arrangement and types of atoms in a single molecule of salicylic acid.
Salicylic Acid Molar Mass
The molar mass of 2-hydroxybenzoic acid is calculated by adding the atomic masses of all the atoms in its formula. 2-Hydroxybenzoic acid has a molar mass of approximately 138.12 grams per mole. This value is useful for determining the amount of 2-hydroxybenzoic acid in a given quantity or for stoichiometric calculations.
Salicylic Acid Boiling Point
2-Hydroxybenzoic acid has a boiling point of around 211 °C (412 °F). This is the temperature at which 2-hydroxybenzoic acid changes from a liquid to a gas under standard atmospheric pressure. The boiling point is an important physical property that affects the handling and processing of 2-hydroxybenzoic acid.
Salicylic Acid Melting Point
2-Hydroxybenzoic acid has a melting point of approximately 159 °C (318 °F). This is the temperature at which 2-hydroxybenzoic acid changes from a solid to a liquid. The melting point is a crucial characteristic for identifying and purifying 2-hydroxybenzoic acid.
Salicylic Acid Density g/mL
The density of 2-hydroxybenzoic acid is about 1.44 grams per milliliter (g/mL). Density is the measure of mass per unit volume. This property helps determine the concentration or purity of 2-hydroxybenzoic acid in a solution and provides insights into its physical behavior.
Salicylic Acid Molecular Weight
The molecular weight of 2-hydroxybenzoic acid is approximately 138.12 grams per mole. It represents the sum of the atomic weights of all the atoms in a single molecule of 2-hydroxybenzoic acid. The molecular weight is essential for various calculations, such as determining the number of moles or mass of 2-hydroxybenzoic acid in a given sample.
Salicylic Acid Structure
2-Hydroxybenzoic acid has a chemical structure consisting of a benzene ring fused with a carboxylic acid group (-COOH). The benzene ring contains six carbon atoms with alternating single and double bonds. This structure gives 2-hydroxybenzoic acid its unique properties and enables its function in various applications.
Salicylic Acid Solubility
2-Hydroxybenzoic acid is moderately soluble in water, with a solubility of about 2 grams per liter at room temperature. However, it is more soluble in organic solvents like ethanol and ether. The solubility of 2-hydroxybenzoic acid affects its formulation in different products and its ability to dissolve in various solutions.
| Appearance | White crystalline powder |
| Specific Gravity | 1.44 g/mL |
| Color | Colorless |
| Odor | Odorless |
| Molar Mass | 138.12 g/mol |
| Density | 1.44 g/mL |
| Melting Point | 159 °C (318 °F) |
| Boiling Point | 211 °C (412 °F) |
| Flash Point | Not applicable |
| Water Solubility | Moderately soluble |
| Solubility | Soluble in solvent such as ethanol and ether |
| Vapor Pressure | Negligible |
| Vapor Density | Not applicable |
| pKa | 2.98 |
| pH | Approximately 2-3 |
Salicylic Acid Safety and Hazards
2-Hydroxybenzoic acid should be handled with caution due to its potential hazards. It can cause skin and eye irritation, so protective equipment like gloves and goggles should be used when working with it. Ingesting large amounts of 2-hydroxybenzoic acid can be harmful and may lead to gastrointestinal issues. It is important to keep 2-hydroxybenzoic acid away from children and pets. Additionally, prolonged exposure to 2-hydroxybenzoic acid fumes or dust should be avoided, as it may cause respiratory irritation. Proper ventilation should be ensured when using 2-hydroxybenzoic acid in confined spaces. It is crucial to follow safety guidelines and consult safety data sheets for handling and storage instructions.
| Hazard Symbols | GHS07 |
| Safety Description | Causes skin and eye irritation. Avoid ingestion. Use with adequate ventilation. Keep away from children and pets. |
| UN IDs | UN 2812 |
| HS Code | 29182100 |
| Hazard Class | 8 (Corrosive) |
| Packing Group | III |
| Toxicity | Moderately toxic by ingestion. Can cause gastrointestinal irritation. May cause respiratory irritation. |
Salicylic Acid Synthesis Methods
There are several methods for synthesizing 2-hydroxybenzoic acid. One common method is the Kolbe-Schmitt reaction. In this process, sodium phenoxide (formed by reacting phenol with sodium hydroxide) is treated with carbon dioxide under high temperature and pressure. This leads to the formation of 2-hydroxybenzoic acid.
Another method involves the oxidation of phenol using sodium hypochlorite or potassium permanganate in the presence of a catalyst such as copper sulfate or manganese dioxide. This oxidation reaction converts phenol into 2-hydroxybenzoic acid.
Furthermore, 2-hydroxybenzoic acid can be synthesized from methyl salicylate through hydrolysis. Methyl salicylate, obtained from wintergreen oil or birch bark oil, is treated with sodium hydroxide or hydrochloric acid to produce 2-hydroxybenzoic acid.
An alternative method involves the esterification of 2-hydroxybenzoic acid with acetic anhydride to form acetyl2-hydroxybenzoic acid, commonly known as aspirin. This reaction is catalyzed by sulfuric acid or phosphoric acid.
It is worth mentioning that these synthesis methods require proper handling and adherence to safety protocols, as some of the reagents and reaction conditions can be hazardous. The industrial-scale synthesis of 2-hydroxybenzoic acid typically employs more specialized and controlled processes to ensure efficiency and product quality.
Salicylic Acid Uses
2-Hydroxybenzoic acid has a wide range of uses due to its beneficial properties. Here are some common applications:
- Skincare products such as cleansers, toners, and spot treatments widely use 2-hydroxybenzoic acid for its ability to exfoliate the skin, unclog pores, and reduce acne breakouts.
- 2-Hydroxybenzoic acid treats various skin conditions like psoriasis, seborrheic dermatitis, and warts by removing dead skin cells and promoting skin renewal.
- 2-Hydroxybenzoic acid effectively softens and removes thickened skin, making it useful in corn and callus removal products.
- Anti-dandruff shampoos utilize 2-hydroxybenzoic acid’s exfoliating properties to eliminate scalp buildup, reduce dandruff, and alleviate scalp itching and flaking.
- Cosmetic formulations employ 2-hydroxybenzoic acid as a preservative due to its antimicrobial properties, which help extend the shelf life of products.
- Chemical peels use 2-hydroxybenzoic acid to improve skin texture, reduce fine lines, and treat hyperpigmentation by promoting the shedding of the outer layer of skin.
- In horticulture, 2-hydroxybenzoic acid acts as a plant growth regulator, stimulating plant defense mechanisms, enhancing resistance to diseases, and improving overall plant health.
- 2-Hydroxybenzoic acid is used as a food preservative in some products to inhibit the growth of bacteria and fungi.
- 2-Hydroxybenzoic acid serves as a precursor for the synthesis of aspirin (acetyl2-hydroxybenzoic acid), a widely used medication for pain relief, fever reduction, and anti-inflammatory purposes.
- Various laboratory procedures and analyses, including spectrophotometric assays and titrations, utilize 2-hydroxybenzoic acid as a laboratory reagent.
Questions:
Q: What does salicylic acid do?
A: 2-Hydroxybenzoic acid exfoliates the skin, unclogs pores, and reduces inflammation, making it effective in treating acne and other skin conditions.
Q: How to treat a chemical burn on the face from salicylic acid?
A: A: If you experience a chemical burn from 2-Hydroxybenzoic acid, immediately rinse the affected area with cool water, apply a soothing ointment like aloe vera, and seek medical attention if necessary.
Q: How do you know when a wart is gone with salicylic acid?
A: A: The wart will gradually decrease in size, become less raised, and eventually disappear with consistent and proper use of 2-Hydroxybenzoic acid treatment over several weeks or months.
Q: What is salicylic acid?
A: A: 2-Hydroxybenzoic acid is a beta hydroxy acid (BHA) derived from willow bark. It is commonly used in skincare products for its exfoliating and anti-inflammatory properties.
Q: What is a salicylic acid cleanser?
A: A: A 2-Hydroxybenzoic acid cleanser is a facial cleanser that contains salicylic acid as an active ingredient. It helps to unclog pores, reduce acne, and promote clearer skin.
Q: What is Ordinary salicylic acid?
A: A: The Ordinary 2-Hydroxybenzoic acid is a skincare product from the brand The Ordinary that contains salicylic acid as its main ingredient. It is used to treat acne and improve skin texture.
Q: How to use minimalist salicylic acid?
A: A: Apply a small amount of Minimalist 2-Hydroxybenzoic acid to clean, dry skin, focusing on the affected areas. Follow the instructions provided by the brand and gradually increase usage if tolerated.
Q: How to apply salicylic acid?
A: A: Apply 2-Hydroxybenzoic acid directly to clean, dry skin using a cotton swab or applicator, targeting the affected areas. Follow the specific instructions provided by the product or healthcare professional.
Q: Is salicylic acid good for oily skin?
A: A: Yes, 2-Hydroxybenzoic acid is beneficial for oily skin as it helps to control excess oil production, unclog pores, and reduce acne breakouts.
Q: What is salicylic acid for skin?
A: A: 2-Hydroxybenzoic acid is used in skincare for its ability to exfoliate dead skin cells, clear clogged pores, treat acne, and improve overall skin texture and appearance.
Q: How does salicylic acid work?
A: A: 2-Hydroxybenzoic acid works by penetrating the skin and dissolving the bonds between skin cells, allowing for exfoliation. It also has anti-inflammatory properties that help reduce redness and swelling.