What is Resorcinol Definition Preparation Reactions and Uses
Properties of Resorcinol
Physical Properties – It shows following physical properties –
It is white in color and solid at room temperature.
It is soluble in water, alcohol and ether.
Its molar mass is 110 g/mol.
It turns pink on exposure to air, light and iron.
It gives a faint benzene odor.
It is insoluble in chloroform and carbon disulfide.
Its melting point is 110℃.
Its boiling point is 277℃.
Its density is 1.28g/cm3.
Chemical Properties – It shows following chemical properties –
It reduces Fehling’s solution and ammoniacal silver solution.
Phthalic anhydride reaction with resorcinol –
Reaction of Resorcinol With Tert-amyl Alcohol –
Reaction of Resorcinol With Ethyl Acetoacetate –
Reaction of Resorcinol With Formaldehyde –
Production of Resorcinol
Resorcinol is prepared from benzene. It crystallizes from benzene as colorless needles. Production of it from benzene takes place through several steps. It is a classic sulfonate fusion process. In this, benzene is treated with sulfuric acid at 100℃ which gives mono sulfonic acid. Which is converted to m-disulfonic acid with 65% oleum at 85℃. Now m-benzenedisulfonate melts in alkaline medium (NaOH) at 300℃ which gives resorcinol and sodium sulfite. Reaction is given below –
As the above reaction shows one step can be reduced by reacting SO3 directly to benzene.
Applications of Resorcinol
Large scale production of resorcinol itself shows its high demand in the market and usefulness. Few applications of resorcinol are listed below –
It is used in acne treatment.
It is antiseptic and disinfectant so used in treatment of many chronic skin diseases such as eczema, psoriasis etc.
It is used in shampoo as an anti-dandruff agent.
Its 2% solution has been used in the treatment of hay fever and whooping cough.
It protects from UV -rays so used in sunscreens.
It is used in treatment of gastric ulcers.
It is used in many medicated soaps as well.
It is used in the production of diazo dyes, plasticizers and resins.
It is used as an analytical reagent for qualitative determination of ketoses.
It is used in explosive materials as well.
It is used in synthesis of raw materials for aerogel.
As it can withstand a wide range of temperatures So,
it is used in the automotive industry as well.
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FAQs on Resorcinol Structure Properties and Chemical Reactions
1. What is resorcinol in chemistry?
Resorcinol is a dihydroxybenzene compound with the molecular formula C6H6O2, where two hydroxyl (–OH) groups are attached to a benzene ring in the 1,3-positions. It is also called 1,3-benzenediol or m-dihydroxybenzene.
- It belongs to the class of phenols.
- The –OH groups are positioned meta to each other.
- It appears as a white crystalline solid and is soluble in water and alcohol.
2. What is the structural formula of resorcinol?
The structural formula of resorcinol is a benzene ring with two –OH groups at the 1 and 3 positions, written as HO–C6H4–OH (1,3-substitution).
- Molecular formula: C6H6O2
- IUPAC name: benzene-1,3-diol
- The meta arrangement distinguishes it from catechol (1,2-diol) and hydroquinone (1,4-diol).
3. Is resorcinol an acid or a base?
Resorcinol is a weak acid because its phenolic –OH groups can donate protons (H+) in aqueous solution.
- It behaves as a phenolic compound, not as a strong acid like HCl.
- It forms phenoxide ions in the presence of strong bases, e.g., with NaOH:
C6H4(OH)2 + 2NaOH → C6H4(ONa)2 + 2H2O - The acidity is due to resonance stabilization of the phenoxide ion.
4. What are the physical properties of resorcinol?
Resorcinol is a white crystalline solid that is highly soluble in water and polar organic solvents.
- Molecular formula: C6H6O2
- Molar mass: approximately 110.11 g·mol−1
- Melting point: about 110 °C
- It has a faint characteristic odor and can darken on exposure to air due to oxidation.
5. How is resorcinol prepared industrially?
Resorcinol is industrially prepared by the fusion of benzene-1,3-disulfonic acid with sodium hydroxide followed by acidification.
- Step 1: Alkaline fusion forms sodium resorcinate.
- Step 2: Acidification with dilute acid yields resorcinol.
- This method replaces sulfonic acid groups (–SO3H) with hydroxyl (–OH) groups.
6. What is the difference between resorcinol, catechol, and hydroquinone?
Resorcinol, catechol, and hydroquinone are positional isomers of dihydroxybenzene that differ in the positions of their –OH groups on the benzene ring.
- Resorcinol: 1,3-dihydroxybenzene (meta position).
- Catechol: 1,2-dihydroxybenzene (ortho position).
- Hydroquinone: 1,4-dihydroxybenzene (para position).
- All have the same molecular formula C6H6O2 but different chemical properties due to structural arrangement.
7. Does resorcinol undergo electrophilic substitution reactions?
Yes, resorcinol readily undergoes electrophilic aromatic substitution because the –OH groups strongly activate the benzene ring.
- The –OH groups are ortho/para-directing substituents.
- It easily reacts in bromination, nitration, and sulfonation reactions.
- Example (bromination in aqueous medium):
C6H4(OH)2 + 3Br2 → C6HBr3(OH)2 + 3HBr
8. What are the common uses of resorcinol?
Resorcinol is widely used in pharmaceuticals, resins, and dye manufacturing due to its reactive phenolic structure.
- Used in antiseptic creams and dermatological preparations.
- Used to produce resorcinol–formaldehyde resins.
- Acts as an intermediate in the synthesis of dyes and UV-absorbing compounds.
9. What happens when resorcinol reacts with formaldehyde?
Resorcinol reacts with formaldehyde to form resorcinol–formaldehyde resin, a thermosetting polymer.
- The reaction involves condensation between phenolic –OH groups and formaldehyde (HCHO).
- Methylene bridges (–CH2–) link aromatic rings.
- The resin is used in adhesives, laminates, and rubber bonding.
10. Why is resorcinol more reactive than benzene?
Resorcinol is more reactive than benzene in electrophilic substitution because its two –OH groups strongly donate electrons through resonance.
- The –OH groups increase electron density on the aromatic ring.
- This activation stabilizes the intermediate sigma complex.
- As a result, reactions such as bromination occur faster and under milder conditions than in benzene.
