reaction+mechanisms

Reaction Mechanisms in Organic Chemistry

There are literally hundreds of different types of chemical reactions in organic chemistry, but they all have a standard way of showing you what is happening during the reaction, called a reaction mechanism.

These mechanisms show how electrons - in pairs or individually - are "flowing" from one atom or bond to another, and in the process, forming new bonds while breaking old ones.

This electron "flow", sometimes called "electron pushing", is represented using arrows. These arrows come in two forms:
 * half-arrows represent the flow of individual electrons (like in orbital notation)
 * whole arrows represent the flow of a pair of electrons

Here are two examples of "electron pushing":



There are a few common electron exchanges or interactions that can occur:
 * homogenesis - the formation of a bond from two single electrons (two merging half-arrows)
 * homolysis - the breaking of a bond into two single electrons (two separating half-arrows)
 * heterogenesis - the formation of a bond from an electron pair to an atom (one merging whole arrow)
 * heterolysis - the breaking of a bond to form an electron pair on an atom (one leaving half arrow)

Take a look at these examples:

Here is a video that describes these processes:

media type="youtube" key="WaHRfIsi-SU" height="315" width="420"

Here is another that describes some more mechanisms:

media type="youtube" key="LwFOPSItocc" height="315" width="560"