Aliphatic ketones : The compounds in which 
group is attached to two alkyl groups are called aliphatic ketones.
Ketones are classified into two types :
1. Simple or symmetrical ketones and
2. mixed or unsymmetrical ketones.
1. Simple or symmetrical ketone :
The ketone in which the carbonyl carbon is attached to two identical alkyl groups is called a simple or symmetrical ketone.
2. Mixed or unsymmetrical ketone :
The ketone in which the carbonyl carbon is attached to two different alkyl groups is called a mixed or unsymmetrical ketone.
