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Chemistry · Grades 10–12

Carboxylic acids and esters

Identify structural differences without laboratory synthesis instructions.

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Learn the idea

Acid group

A carboxylic acid has –C(=O)OH.

Ester group

An ester has –C(=O)OR, where R is a carbon-containing group.

Names

Simple ester names have an alkyl portion from the alcohol-related side and a carboxylate portion.

Conceptual change

Esterification and hydrolysis are reaction classes; predicting a class is not a practical preparation procedure.

Worked examples

Which group distinguishes an ester from a carboxylic acid?

R–C(=O)OH and R–C(=O)OR′ differ at the oxygen substituent.

The acid hydroxyl H is replaced by a carbon-containing group.

CH₃COOCH₂CH₃ is called what in the simple naming scheme?

The oxygen-bound group is ethyl and the acyl portion is ethanoate.

Ethyl ethanoate.

Check your understanding

  1. How many oxygen atoms are in a simple ester group –C(=O)O–?

  2. Which formula pattern is a carboxylic acid?

    1. RCOR′.
    2. RCOOH.
    3. ROR′.

  3. Why is a fruity smell not a reliable way to identify an unknown ester?

Answers and marking notes

Answers and marking notes
  1. 2

    One carbonyl oxygen and one single-bonded oxygen are present.

  2. RCOOH.

    The –COOH group identifies the acid.

  3. Many substances have overlapping odors, and directly smelling unknown chemicals is unsafe.

    Identification needs safe evidence, not smell testing.

Further reading and review references

These are reference links, not copied exercises, institutional endorsement or proof of independent review.

Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.