Benzoic Acid - Overview, Structure, Preparation, Properties & Uses, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:26 PM IST

Benzoic acid is an organic compound with C₆H₅COOH as its chemical formula. It consists of a benzene ring and a carboxylic group. The compound exists in normal conditions as a colourless crystalline solid. Benzoic acid is an organic compound that is used in our daily life for various food and cosmetic products. It is used in many products such as pickles, jams, lipsticks, wash creams, among others. In addition, it is an essential precursor in many organic combination syntheses.

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Benzoic acid structure :
Preparation of benzoic acid
Chemical properties of benzoic acid
Uses of benzoic acid

Benzoic acid

Benzoic acid structure :

The Benzoic acid is also known as Benzene carboxylic acid. There are 7 carbon atoms, 2 oxygen atoms and 6 hydrogen atoms in its structure. It consists of a six-carbon ring with alternate single and double bands, as well as the group of –COOH attached to the ring that makes it benzoic acid.

Benzoic acid formula: C₆H₅COOH

The benzoic acid structure is given below:

Benzoic acid Benzoic acid 3D

Preparation of benzoic acid

In the process of preparation of benzoic acid, we convert Phenol to benzoic acid.

First we convert phenol to benzene using zinc dust and then we convert benzene to Tolune using the CH₃Cl+AlCl₃, here aluminum trichloride acts as lewis acid catalyst.

Then Toluene is converted into benzoic acid by oxidation.

Preparation of Benzoic acid

Resonating structure of benzoic acid or Resonance structure of benzoic acid (Resonating structure of benzaldehyde)

Resonating structure of benzoic acid

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Physical properties of benzoic acid

In its solid state of crystalline nature, benzoic acid reaction has an uncoloured appearance. It is nonclinical in its crystal structure.
This compound is slightly pleasant because of the aromatic ring.
This compound's density decreases to 1,075 gram per cubic centimeter at a temperature of 130^oC.
Benzoic acid melting point of benzoic acid is 122.3⁰C.
Benzoic acid molar mass - 122.12 g/mol.

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Chemical properties of benzoic acid

The solubility is 3.44 g/L and 56.31 g/l, respectively, at a temperature range of 25^oC and 100^oC.
Benzene, carbon tetrachloride, acetone and alcohol are soluble.
The benzoic acid p^ka dissociation constant is 4.2.
The carboxyl group or even the aromatic Ring may experience its reactions.

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Uses of benzoic acid

It is used in an acidic medium, but it has lost preservation activity in an alkaline medium because it divides into ions in an alkaline medium.

The use of benzoic acid as a preservative does not affect the odour or taste of food products.
It delays the reproduction of microorganisms by preserving the quality.
The benzoic acid sodium salt sodium benzoate reduces the blood level of glycine because it is an amide bond between the benzoate and glycine that is excreted by the urinary tract.
Some benzoic acid esters act as plasticizers.
For many foodstuffs such as soda, barbecue sauces, pickle, and dressings which prevent the growth of bacteria and fungi, benzoic acid and its sodium salt are used as food preservatives.
Benzoic acid is used to treat skin irritation, sunburns, insect bites, fungal infections. This is used specifically in cosmetics.
It is used as a pH adjuster in the preparation of fragrances.
It is mostly used in acidic foods because even at very low pH it has more anti-food and antibacterial properties.

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Frequently Asked Questions (FAQs)

1. What is benzoic acid used for?

Benzoic Acid is a white, crystalline powder having a pleasant odour. It is used to make chemicals which are further used in perfumes and flavourings. It is also used as a food preservative and anti- fungal agent.

2. Is benzic acid soluble in water ?

It is an aromatic acid, moderately strong white crystalline powder, highly soluble in alcohol, ether, and benzene, but poorly soluble in water.

3. What is another name for benzoic acid?

Another name for benzoic acid is benzenecarboxylic acid.

4. How to convert benzoic acid to benzamide?

First we convert benzoic acid to benzoyl chloride using SOCl₂ . Then we convert the obtained Benzoyal chloride to benzamide by treating it with NH₃ .

5. What is the formula of benzoic acid?

Benzoic acid is an organic compound with a chemical formula of C₇H₆O₂ or C₆H₅COOH.

6. What is benzoic acid and why is it important in organic chemistry?

Benzoic acid is an aromatic carboxylic acid with the formula C6H5COOH. It's important in organic chemistry as a simple aromatic acid, serving as a model compound for understanding carboxylic acid reactions and properties. It's also widely used in industry and occurs naturally in many plants.

7. How does the presence of substituents on the benzene ring affect the acidity of benzoic acid derivatives?

Substituents on the benzene ring can significantly affect the acidity of benzoic acid derivatives. Electron-withdrawing groups (like -NO2 or -Cl) increase acidity by stabilizing the conjugate base, while electron-donating groups (like -CH3 or -OH) decrease acidity by destabilizing the conjugate base.

8. How does benzoic acid participate in electrophilic aromatic substitution reactions?

Benzoic acid can undergo electrophilic aromatic substitution reactions on its benzene ring. However, the carboxyl group is meta-directing and deactivating, meaning substitutions preferentially occur at the meta position relative to the carboxyl group, and the reactions are slower compared to benzene.

9. How does benzoic acid participate in Friedel-Crafts acylation reactions?

Benzoic acid itself doesn't directly participate in Friedel-Crafts acylation. However, its acid chloride derivative, benzoyl chloride, is commonly used as an acylating agent in these reactions. The carboxyl group of benzoic acid deactivates the ring towards electrophilic substitution, making it a poor substrate for this reaction.

10. How does benzoic acid behave in Friedel-Crafts alkylation reactions?

Benzoic acid is generally not a good substrate for Friedel-Crafts alkylation. The carboxyl group strongly deactivates the ring towards electrophilic substitution and directs incoming groups to the meta position. Additionally, the acidic proton can interfere with the Lewis acid catalyst typically used in these reactions.

11. Why is benzoic acid considered a weak acid despite having a carboxyl group?

Although benzoic acid has a carboxyl group, it's considered a weak acid because it doesn't fully dissociate in water. The benzene ring adjacent to the carboxyl group stabilizes the molecule, making it less likely to release protons compared to stronger acids like hydrochloric acid.

12. How does the melting point of benzoic acid compare to other carboxylic acids, and why?

Benzoic acid has a relatively high melting point (122°C) compared to many other carboxylic acids. This is due to strong intermolecular hydrogen bonding between the carboxyl groups and the planar structure of the molecule, which allows for efficient packing in the solid state.

13. What is the significance of benzoic acid's pKa value?

The pKa of benzoic acid is about 4.2, which indicates its strength as an acid. This value is important for understanding its behavior in solutions, its ability to form salts, and its effectiveness as a preservative. It's stronger than most carboxylic acids due to the stabilizing effect of the benzene ring on the conjugate base.

14. How does benzoic acid behave in aqueous solutions?

In aqueous solutions, benzoic acid partially dissociates into benzoate ions (C6H5COO-) and hydrogen ions (H+). Its solubility in water is limited, but it becomes more soluble in basic solutions as it forms water-soluble benzoate salts.

15. How does the structure of benzoic acid contribute to its properties?

Benzoic acid consists of a benzene ring with a carboxyl group (-COOH) attached. The benzene ring provides stability and aromaticity, while the carboxyl group gives it acidic properties. This combination results in a relatively strong organic acid with unique physical and chemical characteristics.

16. What is the primary industrial method for producing benzoic acid?

The primary industrial method for producing benzoic acid is the partial oxidation of toluene using oxygen and a cobalt or manganese naphthenate catalyst. This process, known as the liquid-phase oxidation of toluene, is efficient and widely used in large-scale production.

17. What is the relationship between benzoic acid and benzaldehyde in terms of oxidation state?

Benzoic acid is the oxidation product of benzaldehyde. The aldehyde group (-CHO) in benzaldehyde is oxidized to a carboxyl group (-COOH) in benzoic acid. This oxidation can occur through various methods, including air oxidation or using stronger oxidizing agents.

18. What are some natural sources of benzoic acid?

Benzoic acid occurs naturally in many plants and some animals. It's found in high concentrations in berries like cranberries and bilberries, as well as in some types of mushrooms. It's also present in dairy products due to the breakdown of hippuric acid in milk.

19. How does benzoic acid behave in Kolbe-Schmitt reactions?

The Kolbe-Schmitt reaction, typically used to synthesize salicylic acid, doesn't directly involve benzoic acid. However, benzoic acid can be a product of side reactions or further oxidation in this process. Understanding this helps in optimizing the synthesis of related compounds.

20. How does the resonance structure of benzoic acid contribute to its stability?

The resonance structure of benzoic acid involves the delocalization of electrons between the benzene ring and the carboxyl group. This resonance stabilization contributes to the overall stability of the molecule, affecting its reactivity and physical properties.

21. What role does benzoic acid play in the food industry?

Benzoic acid and its salts, particularly sodium benzoate, are widely used as food preservatives. They inhibit the growth of mold, yeast, and some bacteria, extending the shelf life of many food products. It's effective in acidic foods and beverages due to its optimal antimicrobial activity at low pH.

22. What is the difference between benzoic acid and sodium benzoate in terms of solubility and uses?

Benzoic acid is poorly soluble in water, while sodium benzoate is highly water-soluble. Due to this, sodium benzoate is more commonly used as a food preservative in aqueous solutions. Benzoic acid is more often used in non-aqueous applications or in products where its lower solubility is beneficial.

23. What is the importance of benzoic acid in biochemistry and metabolism?

In biochemistry, benzoic acid is important as it's involved in the metabolism of many organisms. In humans, it's conjugated with glycine in the liver to form hippuric acid, which is then excreted. This pathway is a key detoxification mechanism and is used to test liver function.

24. How does benzoic acid form esters, and why are these important?

Benzoic acid forms esters through reaction with alcohols in the presence of an acid catalyst. This process, called esterification, produces compounds like methyl benzoate or ethyl benzoate. These esters are important in the fragrance and flavor industries due to their pleasant odors.

25. What is the significance of benzoic acid's sublimation property?

Benzoic acid can sublime, meaning it can transition directly from a solid to a gas without passing through the liquid phase. This property is useful in purification techniques and can be observed in some applications. It's also an interesting physical property that distinguishes it from many other organic compounds.

26. How does benzoic acid react with bases, and what are the products called?

Benzoic acid reacts with bases to form salts called benzoates. For example, the reaction with sodium hydroxide produces sodium benzoate and water. This neutralization reaction is a key aspect of benzoic acid's chemistry and is utilized in various applications, including its use as a food preservative.

27. How does benzoic acid compare to other preservatives in terms of safety and effectiveness?

Benzoic acid is generally recognized as safe (GRAS) by the FDA and is effective against a wide range of microorganisms, particularly in acidic conditions. It's more effective than some preservatives but may have a stronger taste. Its safety profile is well-established, but some individuals may be sensitive to it.

28. What is the role of benzoic acid in organic synthesis?

Benzoic acid is an important starting material and intermediate in organic synthesis. It can be converted into various derivatives, including esters, amides, and acid chlorides. These derivatives are used in the production of plasticizers, dyes, pharmaceuticals, and other organic compounds.

29. How does the hydrogen bonding in benzoic acid affect its physical properties?

Hydrogen bonding in benzoic acid occurs between the hydrogen of the carboxyl group and the oxygen of another benzoic acid molecule. This intermolecular bonding leads to higher melting and boiling points, affects solubility, and influences crystal structure.

30. What is the UV-Vis spectral characteristic of benzoic acid and why is it important?

Benzoic acid shows characteristic absorption in the UV region due to its aromatic ring. This spectral property is important for its identification and quantification in analytical chemistry. It's also relevant in understanding the compound's interaction with light and its potential photochemical reactions.

31. How does benzoic acid behave in non-polar solvents compared to polar solvents?

Benzoic acid is more soluble in non-polar solvents like benzene or chloroform than in water. In non-polar solvents, it often exists as dimers held together by hydrogen bonding. In polar solvents, it may dissociate depending on the solvent's properties and the acid's concentration.

32. What is the mechanism of benzoic acid's antimicrobial action?

Benzoic acid's antimicrobial action primarily occurs in its undissociated form, which can penetrate cell membranes. Inside the cell, it dissociates, acidifying the cell interior and disrupting cellular functions. This mechanism is most effective in acidic environments where more of the acid is undissociated.

33. How does benzoic acid react with reducing agents, and what are the products?

Benzoic acid is relatively resistant to reduction due to the stability of its aromatic ring. However, under strong reducing conditions (like LiAlH4), the carboxyl group can be reduced to form benzyl alcohol. This resistance to reduction is a key difference between aromatic and aliphatic carboxylic acids.

34. What is the importance of benzoic acid in the pharmaceutical industry?

In the pharmaceutical industry, benzoic acid serves as a precursor for many drugs and is used in the synthesis of various medicinal compounds. It's also used as a preservative in some liquid medications and as a pH adjuster in drug formulations.

35. How does the presence of benzoic acid affect the pH of a solution?

As a weak acid, benzoic acid lowers the pH of a solution, but not as dramatically as a strong acid would. The extent of pH change depends on the concentration of benzoic acid and the buffering capacity of the solution. This property is important in its use as a food preservative and pH regulator.

36. What is the significance of benzoic acid's ability to form anhydrides?

Benzoic acid can form anhydrides, such as benzoic anhydride, by reaction with other carboxylic acids or by self-condensation. These anhydrides are important in organic synthesis as acylating agents and in the production of certain polymers and pharmaceuticals.

37. How does the structure of benzoic acid influence its reactivity in nucleophilic acyl substitution reactions?

The carbonyl group of benzoic acid can undergo nucleophilic acyl substitution reactions, but the adjacent benzene ring affects its reactivity. The ring's electron-withdrawing effect makes the carbonyl carbon more electrophilic, but also stabilizes the carboxylate anion, influencing the equilibrium and kinetics of these reactions.

38. What is the role of benzoic acid in the production of plasticizers?

Benzoic acid is used in the production of plasticizers, particularly in the synthesis of diethylene glycol dibenzoate and dipropylene glycol dibenzoate. These compounds are used to increase the flexibility and durability of plastics, especially in PVC products.

39. What is the importance of benzoic acid's vapor pressure in its applications?

Benzoic acid's vapor pressure is relatively low for a compound of its size, which is important for its use as a preservative. This property ensures that it doesn't easily evaporate from products, maintaining its effectiveness over time. It also influences its sublimation behavior and storage requirements.

40. How does benzoic acid interact with proteins, and why is this significant?

Benzoic acid can interact with proteins through hydrogen bonding and hydrophobic interactions. This is significant in its role as a preservative, as these interactions can affect enzyme activity and microbial cell functions. It's also relevant in understanding potential allergic reactions or sensitivities to benzoic acid.

41. What is the environmental impact of benzoic acid production and use?

The environmental impact of benzoic acid is generally considered low. It's biodegradable and doesn't persist in the environment. However, its production from toluene involves organic solvents and catalysts, which require proper handling and disposal. Its widespread use in consumer products also necessitates monitoring of environmental levels.

42. How does benzoic acid behave in photochemical reactions?

Benzoic acid can undergo photochemical reactions, particularly when exposed to UV light. These reactions can include decarboxylation to form benzene or rearrangements to form other products. Understanding these reactions is important for storage, handling, and potential applications in photochemistry.

43. What is the role of benzoic acid in the synthesis of dyes and pigments?

Benzoic acid and its derivatives are used in the synthesis of various dyes and pigments. For example, it's a precursor in the production of some azo dyes. The carboxyl group can be modified or used as a point of attachment for chromophores, influencing color properties.

44. How does benzoic acid compare to salicylic acid in terms of structure and properties?

Benzoic acid and salicylic acid are both aromatic carboxylic acids, but salicylic acid has an additional hydroxyl group ortho to the carboxyl group. This gives salicylic acid unique properties, including increased acidity and the ability to form intramolecular hydrogen bonds, affecting its melting point and solubility compared to benzoic acid.

45. What is the significance of benzoic acid's conjugate base in buffer solutions?

The conjugate base of benzoic acid, the benzoate ion, forms part of a buffer system when present with benzoic acid. This buffer can help maintain a relatively constant pH in solutions, which is important in various chemical and biological systems, including some food products and pharmaceuticals.

46. How does benzoic acid participate in esterification reactions, and what factors affect the equilibrium?

Benzoic acid undergoes esterification with alcohols to form esters. This reaction is typically acid-catalyzed and reversible. The equilibrium is affected by factors such as the relative concentrations of reactants and products, temperature, and the removal of water (a product of the reaction) to drive the equilibrium towards ester formation.

47. What is the importance of benzoic acid in studying reaction mechanisms in organic chemistry?

Benzoic acid serves as a model compound for studying various reaction mechanisms in organic chemistry. Its relatively simple structure, combined with the reactivity of the carboxyl group and the stability of the aromatic ring, makes it useful for understanding concepts like nucleophilic acyl substitution, electrophilic aromatic substitution, and carboxylic acid reactions.

48. What is the role of benzoic acid in the synthesis of benzoyl peroxide, and why is this compound important?

Benzoic acid is a precursor in the synthesis of benzoyl peroxide. It's first converted to benzoyl chloride, which then reacts with hydrogen peroxide to form benzoyl peroxide. This compound is important as an initiator in radical polymerization reactions and is also used in acne treatments and as a bleaching agent.

49. How does the presence of benzoic acid affect the boiling point of solutions?

Benzoic acid, being a non-volatile solute, increases the boiling point of solutions it's dissolved in. This colligative property depends on the concentration of benzoic acid and is more pronounced in polar solvents where it may dissociate. Understanding this is important in applications like distillation and in studying solution properties.

50. What is the significance of benzoic acid's ability to form coordination compounds with metals?

Benzoic acid can form coordination compounds with