An unsymmetrical ketone such as 2-methylcyclohexanone can form two possible enolates. Just which enolate is formed predominantly depends on the base used and on the conditions employed. The enolate with the more highly substituted double bond is the thermodynamically more stable enolate in the same way that an alkene with the more highly substituted double bond is the more stable alkene. this enolate, called the thermodynamic enolate, is formed predoninantly under conditions that permit the establishment of an equilibrium. this will generally be the case if the enolate is produced using a relatively weak base n a protic solvent.
On the other hand the enolate with the less substituted double bond is usually formed faster, because removal of the hydrogen necessary to produce this enolate is less sterically hindered. this enolate, called the kinetic enolate, is formed predominantly when the reaction is kinetically controlled (or rate controlled). ltBrgt The kinetically favored enolate can be formed cleanly through the use of lithium diisopropylamide (LDA). this strong, sterically hindered base rapidly removes the proton from the less substituted `alpha` carbon of the ketone. the following, using 2-methylcyclohexanone, is an illustration. the solvent for the reaction is 1,2-dimethoxyethane `(CH_(3)OCH_(2)CH_(2)OCH_(3))`, abbeviated DME. the LDA removes the hydrogen from the `-CH_(2)-alpha` carbon jmore rapidly because it is less hindered (and because there are twice as many hydrogens there to react).
product (A) is 
