What's the role of intermediates in reaction mechanisms?

Intermediates in reaction mechanisms act as temporary species that are formed and consumed during the reaction process.

In more detail, intermediates are molecules or ions that are produced in one step of a reaction mechanism and consumed in a subsequent step. They are not present in the overall balanced chemical equation for the reaction, as they are formed and used up during the reaction process. This is what distinguishes them from reactants, which are consumed, and products, which are formed in a chemical reaction.

Intermediates play a crucial role in reaction mechanisms as they help to explain how a reaction occurs at a molecular level. They are often involved in the rate-determining step of a reaction, which is the slowest step in a reaction mechanism and determines the overall rate of the reaction. By studying the intermediates and the steps in which they are involved, chemists can gain a better understanding of the reaction mechanism and how to control or manipulate it.

For example, in the reaction mechanism for the formation of sulphuric acid, the sulphur trioxide (SO3) that is formed in the first step is an intermediate. It reacts with water in the second step to form sulphuric acid, which is the final product. By understanding the role of this intermediate, chemists can control the conditions of the reaction to optimise the production of sulphuric acid.

In addition, intermediates can also be used to identify the pathway of a reaction. If an intermediate is detected during a reaction, it can provide evidence for a particular reaction pathway. For instance, if a certain intermediate is detected during a reaction, it can suggest that the reaction is proceeding via a certain mechanism rather than another.

In conclusion, intermediates are crucial in understanding and controlling chemical reactions. They provide insight into the steps of a reaction mechanism, the rate of the reaction, and the pathway of the reaction.