What is the Difference Between Azomethines and Ketimines?

Azomethines and ketimines are both types of imines, which are compounds containing a carbon-nitrogen double bond (C=N). The main difference between azomethines and ketimines lies in their structure and the way they are formed:

Azomethines: These are secondary aldimines, which means they have a carbon atom in the functional group. They are formed as a result of the reaction of primary amines with aldehydes. Examples of azomethines include anilines, which are derived from anilines.
Ketimines: These are a type of imine where two hydrocarbyl groups are attached to the carbon atom of the N=C bond. Ketimines can be classified as primary or secondary, depending on whether the nitrogen atom is bonded to a hydrogen atom or an organic group other than the C=N bond. Ketimines are formed as a result of the reaction with ketones.

Both azomethines and ketimines are types of Schiff bases, which are compounds with the general structure R1R2C=NR3. They can be considered subclasses of imines, being either secondary ketimines or secondary aldimines depending on their structure. Some similarities between azomethines and ketimines include:

Both are types of imines.
Both contain hydrocarbyl groups.

However, there are differences in their chemical properties, such as basicity. Schiff bases show weaker basic properties compared to their corresponding amines due to the change in hybridization from sp3 to sp2 when the imine structure is formed.