Carbolic acid is the common name for phenol. Its chemical formula is C₆H₅OH (or C₆H₅-OH). The IUPAC name is hydroxybenzene or phenol. It is an aromatic organic compound consisting of a benzene ring bonded to a hydroxyl group (-OH). Molecular mass = 94 g/mol. Carbolic acid was historically important as the first antiseptic used in surgery by Joseph Lister in 1865.
Carbolic acid = Phenol; Formula: C₆H₅OH.
IUPAC name: Hydroxybenzene. Molecular mass: 94 g/mol.
Structure: Benzene ring + hydroxyl group (-OH).
Joseph Lister (1865): first used carbolic acid as an antiseptic in surgery.
Phenol is a weak acid (pKa = 9.95).
Reacts with Br₂(aq) to give 2,4,6-tribromophenol (white precipitate) — test for phenol.
Used to make Bakelite (phenol + formaldehyde) — first synthetic plastic.
Phenol was first extracted from coal tar (hence 'carbolic').
Chemical name: Phenol (common name: Carbolic Acid) Chemical formula: C₆H₅OH Alternate formula: C₆H₅-OH or C₆H₆O IUPAC name: Hydroxybenzene Molecular mass: 94 g/mol
Structure: • Phenol = Benzene ring (C₆H₅-) + Hydroxyl group (-OH) • The -OH group is directly attached to the benzene ring • The benzene ring makes phenol aromatic
Breaking down the formula: • C₆H₅ = phenyl group (benzene ring with one H removed) • OH = hydroxyl group • C₆H₅OH = phenol (6 carbons + 5 hydrogens + 1 OH) Atoms: C=6, H=6, O=1
Physical properties: • Melting point: 40.5°C (solid at room temp) • Boiling point: 181.7°C • Appearance: Colourless to light pink crystalline solid • Solubility: Slightly soluble in water; miscible with organic solvents • Odour: Distinctive sweet, somewhat medicinal/antiseptic smell
Why called 'Carbolic Acid': • 'Carbo' = coal/carbon (phenol was first extracted from coal tar in the 19th century) • 'Olic' = oil-like • Phenol was isolated from coal tar distillation • It was used as an antiseptic and disinfectant — hence the name 'carbolic acid'
Joseph Lister and Carbolic Acid: • In 1865, surgeon Joseph Lister first used carbolic acid (phenol) as an antiseptic • He sprayed it on surgical instruments, wounds, and operating theatres • This dramatically reduced post-surgical infections and deaths • This was the beginning of antiseptic surgery
Acidic nature of phenol: • Phenol is a weak acid (pKa = 9.95) • Ionisation: C₆H₅OH ⇌ C₆H₅O⁻ + H⁺ • Weaker than carbonic acid (H₂CO₃) but stronger than water • Turns blue litmus red (but weakly)
Important reactions: • With NaOH: C₆H₅OH + NaOH → C₆H₅ONa + H₂O (sodium phenoxide) • Bromination: Phenol + Br₂(aq) → 2,4,6-tribromophenol (white precipitate) — used as a test for phenol • Nitration: reacts with conc. HNO₃ to give 2,4,6-trinitrophenol (picric acid)
Uses of phenol/carbolic acid:
Antiseptics and disinfectants: • Dettol (main ingredient: chloroxylenol, related phenol compound) • TCP antiseptic (contains phenol derivatives) • Historical: used in carbolic soap
Manufacturing: • Bakelite: phenol + formaldehyde → thermosetting plastic (first synthetic plastic) • Nylon-6,6 precursor • Aspirin (salicylic acid synthesis) • Pharmaceuticals
Industrial uses: • Manufacture of dyes, paints, adhesives • Wood preservatives (creosote) • Herbicides and pesticides
Warning: Phenol is toxic and corrosive • Causes burns on skin contact • Vapours are harmful if inhaled • Not to be used without proper safety precautions
Carbolic acid (phenol) has the formula C₆H₅OH. IUPAC name: hydroxybenzene. Molecular mass: 94 g/mol. It is an aromatic compound consisting of a benzene ring bonded to a hydroxyl group (-OH).
The IUPAC name of carbolic acid is hydroxybenzene (common name: phenol). Formula: C₆H₅OH. It is classified as a weak acid (pKa = 9.95) that ionises partially in water.
Phenol is called carbolic acid because it was first extracted from coal tar (carbolic = from carbon/coal). It has acidic properties (weak acid, pKa 9.95). The name dates from the 19th century when phenol was identified as a component of coal tar distillate.
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