Benzoic acid is a colorless crystalline solid that is used as a food preservative and as a precursor to many other organic compounds. It can be synthesized from toluene or benzene.
| IUPAC Name | Benzoic acid |
| Molecular Formula | C7H6O2 |
| CAS Number | 65-85-0 |
| Synonyms | Carboxybenzene, Benzeneformic acid, Phenylformic acid, Benzenecarboxylic acid, E210 |
| InChI | InChI=1S/C7H6O2/c8-7(9)6-4-2-1-3-5-6/h1-5H,(H,8,9) |
Benzoic acid molar mass
Benzoic acid has a molar mass of 122.12 g/mol. It is a simple organic compound that consists of a benzene ring attached to a carboxylic acid functional group. The molar mass is calculated by adding the atomic masses of all the atoms present in a single molecule of the compound. In the case of benzoic acid, the formula is C7H6O2, so the molar mass can be calculated as
7(12.01) + 6(1.01) + 2(16.00) = 122.12 g/mol
Knowing the molar mass is important in determining the amount of benzoic acid needed in chemical reactions and in calculating other properties such as concentration and density.
Benzoic acid structure
The structure of benzoic acid consists of a benzene ring attached to a carboxylic acid functional group. The benzene ring is a six-membered carbon ring with alternating double bonds, while the carboxylic acid group consists of a carbon atom double-bonded to an oxygen atom and a single-bonded to a hydroxyl group. The structure of benzoic acid is important in determining its chemical and physical properties.
Benzoic acid formula
The chemical formula of benzoic acid is C7H6O2. This formula tells us that each molecule of benzoic acid contains seven carbon atoms, six hydrogen atoms, and two oxygen atoms. The formula is used to determine the molar mass and molecular weight of benzoic acid, as well as the ratio of the elements present in the compound.
Benzoic acid melting point
Benzoic acid has a melting point of 122.4 °C. This is the temperature at which the solid form of benzoic acid begins to melt and turn into a liquid. The melting point is affected by factors such as purity, crystal structure, and intermolecular forces. Benzoic acid has a relatively high melting point due to its strong intermolecular forces, which are caused by hydrogen bonding between the carboxylic acid groups in adjacent molecules.
BzOH boiling point
The boiling point of BzOH is 249 °C. This is the temperature at which the liquid form of BzOH begins to vaporize and turn into a gas. The boiling point of a substance is affected by factors such as intermolecular forces, pressure, and the presence of impurities. BzOH has a relatively high boiling point due to its strong intermolecular forces, which are caused by hydrogen bonding between the carboxylic acid groups in adjacent molecules.
BzOH density g/ml
The density of BzOH is 1.265 g/mL. This is the mass of one milliliter of BzOH at a specific temperature and pressure. Density is an important physical property that is used to determine the mass of a substance in a given volume. The density of BzOH is affected by factors such as temperature and pressure.
BzOH molecular weight
The molecular weight of BzOH is 122.12 g/mol. This is the mass of one molecule of BzOH. The molecular weight is used to determine the number of molecules in a given mass of a substance. It is calculated by adding the atomic masses of all the atoms in the molecule.
| Appearance | White crystals |
| Specific Gravity | 1.265 g/cm³ |
| Color | Colorless |
| Odor | Faint, pleasant |
| Molar Mass | 122.12 g/mol |
| Density | 1.265 g/cm³ |
| Melting Point | 122.4 °C |
| Boiling Point | 249 °C |
| Flash Point | 121 °C |
| Water Solubility | 3.8 g/L |
| Solubility | Soluble in ethanol, ether, benzene, and chloroform; slightly soluble in water |
| Vapour Pressure | 0.00027 mmHg at 25°C |
| Vapour Density | 4.2 (air=1) |
| pKa | 4.2 |
| pH | 2.7 – 3.5 |
Benzoic Acid Safety and Hazards
Benzoic acid (BzOH) can pose hazards if handled improperly. It is a skin and eye irritant, and can cause respiratory irritation if inhaled in high concentrations. Ingesting large amounts of BzOH can also cause nausea, vomiting, and abdominal pain. The compound is flammable and can ignite if exposed to heat or flames. It is important to handle BzOH with care, wearing appropriate protective equipment and avoiding contact with skin, eyes, and mucous membranes. In case of accidental exposure, affected areas should be rinsed with water and medical attention sought if necessary. Proper storage and disposal procedures should also be followed to prevent environmental contamination.
| Hazard Symbols | Xi |
| Safety Description | Avoid contact with skin and eyes; Wear protective gloves/eye protection; In case of contact with eyes, rinse immediately with plenty of water and seek medical advice; Store in a dry place away from heat and incompatible materials; Keep containers tightly closed. |
| UN Ids | UN 3077 (ADR/RID), UN 1220 (IMDG), UN 3077 (ICAO) |
| HS Code | 2916.31.00 |
| Hazard Class | 9 (Miscellaneous dangerous substances and articles) |
| Packing Group | III |
| Toxicity | Benzoic acid is relatively non-toxic, with an oral LD50 in rats of 1700-1940 mg/kg. It may cause skin and eye irritation and respiratory irritation if inhaled in high concentrations. Ingesting large amounts can also cause gastrointestinal distress. |
Benzoic Acid Synthesis Methods
One can synthesize benzoic acid (BzOH) through various methods.
One common method is the oxidation of toluene or benzyl chloride using potassium permanganate or chromic acid. Another method involves the reaction of benzene with carbon dioxide and a metal catalyst, such as copper or magnesium oxide, in the presence of heat and pressure.
One can obtain BzOH through hydrolysis of benzamide, benzoyl chloride, or benzotrifluoride using a strong base, such as sodium hydroxide. This process yields BzOH and the corresponding amine or alcohol. Alternatively, one can obtain BzOH by reacting benzyl alcohol with potassium permanganate or sodium dichromate.
One can use a Grignard reagent, formed by reacting magnesium and an alkyl or aryl halide, with carbon dioxide to synthesize BzOH. To convert the resulting carboxylic acid to BzOH, one can acidify the solution.
One can produce BzOH by oxidizing toluene in the presence of a cobalt or manganese catalyst. This method is particularly useful for large-scale production.
Each of these synthesis methods has advantages and disadvantages depending on the specific application and scale of production. It is important to choose the most appropriate method based on factors such as cost, efficiency, and environmental impact.
Benzoic Acid Uses
- People commonly use Benzoic acid (BzOH) as a food preservative because it can inhibit the growth of bacteria and fungi.
- Manufacturers use it as an intermediate in the synthesis of various chemicals, including dyes, fragrances, and pharmaceuticals.
- Producers use BZOH in the manufacture of plasticizers, such as benzyl benzoate, which find use in the production of PVC and other plastics.
- It plays a vital role in the production of phenol, which is used in the manufacture of resins, adhesives, and disinfectants.
- Manufacturers add BZOH in animal feed to prevent the growth of mold and bacteria.
- It acts as a precursor to benzoyl peroxide, which finds use in the treatment of acne.
- Producers use BZOH in the production of various types of polymers, including polyester, nylon, and polyurethane.
- Industries use it as a solvent for various organic compounds, including resins, oils, and waxes.
- Manufacturers use BZOH in the production of various types of salts, such as sodium benzoate, which find use as food preservatives and antimicrobial agents.
- BZOH is used in the production of various types of detergents, including laundry detergents, dishwashing detergents, and cleaning agents.
Questions:
Q: Is benzoic acid soluble in water?
A: BzOH is sparingly soluble in water, with a solubility of 3.4 g/L at 25°C. However, it is more soluble in organic solvents such as ethanol and acetone.
Q: Is benzoic acid a strong acid?
A: No, BzOH is a weak acid. In water, it partially dissociates to form hydronium ions and benzoate ions. Its dissociation constant (Ka) is 6.5 x 10^-5, indicating its weak acidic nature.
Q: A solution of benzoic acid (C6H5COOH) that is 0.20 M has a pH of 2.45. What is Ka for benzoic acid?
A: The Ka for BzOH can be calculated using the pH of the solution and the concentration of the acid. Using the pH of 2.45 and the equation for the dissociation of BzOH, the Ka is calculated to be 6.5 x 10^-5.
Q: Is benzoic acid polar or nonpolar?
A: Benzoic acid is a polar molecule due to the presence of the carboxylic acid functional group, which contains an electronegative oxygen atom that creates a dipole moment