Study Guides/Chemistry/Formula of Ketone
Study Guide · Chemistry

Formula and Structure of Ketones

In Organic Chemistry, a Ketone is a functional group characterized by a carbonyl group (C=O) bonded to two other carbon atoms. It is a very important topic in Class 10 (Carbon and its Compounds) and Class 11 Chemistry.

Question (Click to Flip)

What is the general formula of a ketone?

Answer

The general structural formula is R-CO-R', and the general molecular formula is CnH2nO (where n is 3 or more).

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Key Facts

Functional Group: -C(=O)- (Carbonyl group in the middle of a chain).

General Formula: CₙH₂ₙO (where n ≥ 3).

Smallest Ketone: Propanone (Acetone).

Difference from Aldehyde: Aldehydes have the C=O at the END of the chain; Ketones have it in the MIDDLE.

General Formula of a Ketone

The general structural formula for a ketone is: R - C(=O) - R'

Where:

  • C=O is the carbonyl group.
  • R and R' are alkyl groups (carbon chains). They can be the same or different.

Note: In a ketone, the C=O group can NEVER be at the end of the chain (if it is at the end, it becomes an Aldehyde).

General Molecular Formula

For open-chain, saturated ketones, the general molecular formula is: CₙH₂ₙO (Where n must be greater than or equal to 3).

The Simplest Ketone: Acetone

Because a ketone needs at least two alkyl groups surrounding the C=O group, the smallest possible ketone must have 3 carbon atoms.

  • IUPAC Name: Propanone
  • Common Name: Acetone (used in nail polish remover)
  • Formula: CH₃-CO-CH₃

Questions and Answers

What is the general formula of a ketone?+

The general structural formula is R-CO-R', and the general molecular formula is CnH2nO (where n is 3 or more).

Which is the simplest ketone?+

The simplest ketone is Propanone (commonly known as Acetone) with the formula CH3COCH3.

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