Skip to main content
Back

Aldehydes, Ketones, and Carboxylic Acids: Structure, Nomenclature, and Common Names

NotesPracticeVideo lessons

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Aldehydes, Ketones, and Carboxylic Acids

Introduction to Carbonyl Compounds

Organic compounds containing a carbon-oxygen double bond (carbonyl group) are fundamental in organic chemistry. The nature of the groups attached to the carbonyl carbon determines whether the compound is an aldehyde, ketone, or carboxylic acid.

  • Aldehydes: The carbonyl group is bonded to at least one hydrogen atom. General formula: R-CHO

  • Ketones: The carbonyl group is bonded to two carbon atoms. General formula: R-CO-R'

  • Carboxylic Acids: The carbonyl group is bonded to a hydroxyl group (-OH). General formula: R-COOH

Structural representations:

  • Aldehyde:

  • Ketone:

  • Carboxylic Acid:

Nomenclature and Structure of Carbonyl Groups

The naming of aldehydes and ketones follows specific rules based on the functional group and the length of the carbon chain.

Aldehydes

  • Functional group:

  • Suffix used: -al (e.g., ethanal, propanal)

  • Prefix used: formyl- (when the group is a substituent)

Ketones

  • Functional group: (carbonyl group within the carbon chain)

  • Suffix used: -one (e.g., propanone, butanone)

  • Prefix used: keto- or oxo- (when the group is a substituent)

Common Names of Aldehydes and Ketones

Many simple aldehydes and ketones are known by their common names, which are often derived from the Latin or Greek names of the corresponding carboxylic acids.

Number of Carbons

Prefix

Example (Aldehyde)

Example (Ketone)

1

Form-

Formaldehyde ()

—

2

Acet-

Acetaldehyde ()

—

3

Propion-

Propionaldehyde ()

—

4

Butyr-

Butyraldehyde ()

—

5

Valer-

Valeraldehyde

—

6

Capro-

Caproaldehyde

—

Examples of Common and IUPAC Names:

  • Formaldehyde (): Methanal

  • Acetaldehyde (): Ethanal

  • Propionaldehyde (): Propanal

  • Butyraldehyde (): Butanal

  • Isobutyraldehyde (): 2-Methylpropanal

  • α-Methylbutyraldehyde (): 3-Methylbutanal

Key Points:

  • The common name is often based on the parent acid, with the suffix -aldehyde for aldehydes.

  • For branched compounds, prefixes such as iso- or α-methyl- indicate the structure.

  • IUPAC names use the longest carbon chain containing the carbonyl group, with the appropriate suffix.

Example: Isobutyraldehyde () is named 2-methylpropanal in IUPAC nomenclature, indicating a three-carbon chain with a methyl group on the second carbon.

Additional info: Carboxylic acids are not detailed in the provided notes, but they also contain the carbonyl group and are named with the suffix -oic acid in IUPAC nomenclature.

Pearson Logo

Study Prep