Question

Write a classification of aliphatic ketones with a suitable example.

Answer 1

On the basis of types of alkyl groups bonded to carbonyl carbon, aliphatic ketones are further classified as simple and mixed ketones.

Simple or symmetrical ketones: The ketones in which both the alkyl groups bonded to carbonyl carbon are identical are called simple ketones or symmetrical ketones.
e.g.

• \[\begin{array}{cc}
  \ce{O}\phantom{.......}\\
  ||\phantom{.......}\\
  \ce{\underset{\text{Dimethyl ketone (Acetone)}}{H3C - C - CH3}}
  \end{array}\]
• \[\begin{array}{cc}
  \ce{O}\\
  ||\\
  \ce{\underset{\text{Diethyl ketone}}{H5C2 - C - C2H5}}
  \end{array}\]

Mixed or unsymmetrical ketones: The ketones in which two alkyl groups bonded to carbonyl carbon are different are called mixed ketones or unsymmetrical ketones.

e.g.

• \[\begin{array}{cc}
  \ce{O}\phantom{..}\\
  ||\phantom{..}\\
  \ce{\underset{\text{Ethyl methyl ketone}}{H5C2 - C - CH3}}
  \end{array}\]
• \[\begin{array}{cc}
  \ce{O}\phantom{.............}\\
  ||\phantom{.............}\\
  \ce{\underset{\text{Ethyl n-propyl ketone}}{H5C2 - C - CH2 -CH2 - CH3}}
  \end{array}\]