Mechanisms

A mechanism is a description of what is actually happening in a reaction at the molecular level.

Before everyone (even grandparents) were on the internet, people stored recipes on index cards kept in a box. Each card would look something like this.

The reactions that we are used to writing are like the left side of this card. On the left we find a list of the ingredients (the reactant) and either on the left or (as in this case) at the top, we find what we're making (the products)

The mechanism is all of the stuff on the right that tells you what you have to do. Sometimes the recipe mechanism is very simple: Mix together. Eat. Sometimes it is much more complex: Mix the dry ingredients. Separate the eggs. Beat the egg whites. Etc.

Reactions mechanism can also be simple or complex. Many reactions occur in one step (Mix and Eat), but others occur in two or more steps.

The graph that represents the energy of a reaction can thus appear somewhat different for a reaction that occurs in multiple steps.

The question then is why do mechanisms matter?

Two real-life examples of mechanisms are here (NO₂ and CO) and here (ozone)

The NO₂ and CO mechanism explains the basics of mechanisms and the ozone mechanism discusses how human activity added a catalyst to the upper atmosphere and its impact on the ozone layer.