In chemistry, chemical synthesis means using chemical reactions to get a product, or several products. This happens by physical and chemical manipulations. Often, several different chemical reactions are used; one after another. In modern laboratory usage, a chemical synthesis is reproducible (if the experiment is done a second time, it will have the same results as the first time), reliable (not broken by small changes in conditions), and established to work in multiple laboratories.
Chemists start to design a chemical synthesis by selecting compounds to combine. These starting chemicals are known as reagents or reactants. Chemists do various things to these reagents to synthesize the product, or an intermediate product. This requires mixing the compounds in a reaction vessel. The vessel can be a chemical reactor or a simple flask. Many reactions require some form of work-up procedure before the final product is isolated.
The amount of product in a chemical synthesis is the reaction yield. Typically, chemical yields are expressed as a weight in grams or as a percentage of the total theoretical quantity of product that could be produced. A side reaction is an unwanted chemical reaction taking place that reduces the yield of the wanted product.
The chemist Adolph Wilhelm Hermann Kolbe was the first to use the word synthesis in its present-day meaning.
In most cases, a single reaction will not convert a reactant (starting chemical) into the desired reaction product. Chemists have many strategies to find the best sequence of reactions to make the desired product. In
cascade reactions multiple chemical changes take place within a single reactant. In
multi-component reactions up to 11 different reactants form a single reaction product. In a
telescopic synthesis, one reactant goes through multiple transformations without isolatingintermediates after each step.