Question

Define what is meant by unimolecular and biomolecular steps. Why are termomolecular steps infrequently seen in chemical reactions?

Short answer

Unimolecular reaction: In a unimolecular reaction, a single reactant decomposes.

Biomolecular reaction: In bimolecular reactions, two molecules react.

In termomolecular reaction, three reactants in correct orientation have to react which is a very rare event.

Step-by-step solution

Understanding the principle of unimolecular and biomolecular reactions.

In a unimolecular reaction, a single reactant simply decomposes into products. In a bimolecular reaction, there are two species (molecules) interacting/reacting to form a product.

Understanding the principle of a termomolecular reaction.

In order for a termomolecular reaction to occur, three reactants in correct orientation have to react which is a very rare event. When these reactions occur, such reactions are often very slow. Thus, termomolecular steps are infrequently seen in chemical reactions.