You already know that an acid and an alcohol can react. But why would they? And what do they make?
Think of a carboxylic acid as a molecule with a "sticky" end — the carboxyl group (−COOH). That end has an -OH group of its own. An alcohol also has an -OH group. If you bring them together with a little help from a strong acid catalyst (like concentrated H2SO4), the -OH from the acid and the -H from the alcohol's -OH group can break off and join to form water. The two remaining fragments snap together, forming a new molecule: an ester.
So the reaction is a kind of condensation — two molecules join by losing a small molecule (water). The catalyst (acid) makes the acid's carbonyl carbon more reactive so the alcohol can attack it.
Note
The water comes from the acid's -OH and the alcohol's -H. The rest of the alcohol's oxygen stays in the ester.
Precise statement:
Esterification is the reversible, acid-catalyzed reaction between a carboxylic acid and an alcohol to produce an ester and water.
The general equation is:
R−COOH+R′−OHheatH+R−COO−R′+H2O
Here, R and R′ are alkyl (or aryl) groups. The R comes from the acid, the R′ from the alcohol. The ester link is −COO−.
R−COOH+R′−OHΔH+R−COO−R′+H2O
Key exam points:
The reaction is reversible — the ester can be hydrolysed back to acid and alcohol (the reverse is called saponification when done with base).
Concentrated H2SO4 acts as both a catalyst and a dehydrating agent (it absorbs the water formed, shifting equilibrium toward products).
The reaction is slow at room temperature; heat is needed.
Esters have characteristic fruity smells — that's why this reaction is used in perfumes and flavourings. …
Acetylation of salicylic acid gives acetylsalicylic acid = aspirin.
Salicylic acid has a phenolic -OH group. When it is acetylated (treated with acetic anhydride/acetyl chloride), the -OH is converted to an acetyl ester (-OCOCH3), forming acetylsalicylic acid:
Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.
CBSE 2026Set ANNUAL1 markMCQ
Q.Acetylation of salicylic acid produces:
(a) Aspirin
(b) DDT
(c) Phenol
(d) BHC
›Reveal solutionSolution
Acetylation of salicylic acid gives acetylsalicylic acid = aspirin.
Salicylic acid has a phenolic -OH group. When it is acetylated (treated with acetic anhydride/acetyl chloride), the -OH is converted to an acetyl ester (-OCOCH3), forming acetylsalicylic acid:
Q.The reaction between Alcohol and Carboxylic Acid is called -
(a) Esterification Reaction
(b) Neutralization Reaction
(c) Acylation Reaction
(d) None of these
›Reveal solutionSolution
Alcohol + carboxylic acid (acid catalysed) gives an ester — this is esterification.
When an alcohol reacts with a carboxylic acid in the presence of a small amount of concentrated H2SO4 (or dry HCl gas) as catalyst, an ester and water are formed. This reaction is called esterification: …
Nylon 6,6 is made from hexamethylenediamine and adipic acid.
Nylon 6,6 is a polyamide formed by condensation polymerisation. Its two monomers each carry six carbon atoms (hence '6,6'): hexamethylenediamine, H2N(CH2)6NH2, and adipic acid, HOOC(CH2)4COOH. Repeated amide ( …
Acid chlorides are highly reactive acylating agents; reacting ethanoyl chloride with ethanol replaces the -Cl with -OC2H5, giving the ester ethyl ethanoate.
MECHANISM (brief): The alcohol's oxygen (nucleophile) attacks the electrophilic carbonyl carbon of the acid chloride, displacing chloride ion; this is a nucleophilic acyl substitution, and acid chlorides undergo it very readily (much faster than the corresponding acid + alcohol, which needs …