In chemistry , chemical synthesis ( or combination) is the artificial execution of useful chemical reactions to obtain one or several products .  It results from physical and chemical manipulations that usually involve one or more reactions. In modern laboratory uses, the procedure is reproducible and reliable.
A chemical synthesis involves one or more compounds ( known as reagents or reactants ) that will undergo transformation when subjected to certain conditions. Various reaction types can be implemented to produce the desired product . This requires mixing the compounds in a reaction vessel such as a chemical reactor or a simple round-bottom flask . Many reactions require some sort of work-up or purification process to separate the final product .
The quantity produced in chemical synthesis is known as the reaction yield . Typically, yields are expressed as a mass in grams (in a laboratory setting) or as a percentage of the total theoretical volume that can be produced based on the limiting reagent . A side reaction is an unwanted chemical reaction that reduces the desired yield. The term synthesis was first used by the chemist Hermann Kolbe .
Several strategies exist in chemical synthesis that go beyond converting reactant A into reaction product B in a single step. In multistep synthesis , a chemical compound is synthesized through a series of separate chemical reactions, each with its own work-up.  For example, the laboratory synthesis of paracetamol may involve three individual synthetic steps. In cascade reactions multiple chemical transformations take place within a single reactant, up to 11 different reactants form a single reaction product and in a telescopic synthesis a reactant undergoes multiple transformations without the separation of the intermediate goes.
Organic synthesis is a special branch of chemical synthesis that deals with the synthesis of organic compounds . In total synthesis of a complex product it may take several steps to synthesize the product of interest and an excessive amount of time. Skill in organic synthesis is prized among chemists and the synthesis of exceptionally valuable or difficult compounds has won chemists such as Robert Burns Woodward the Nobel Prize for Chemistry . If chemical synthesis begins with basic laboratory compounds, it is considered a purely synthetic process. If it starts with a product isolated from plants or animals and then proceeds to new compounds, the synthesis is called semi-synthetic .The process is described as .
Inorganic synthesis and organometallic synthesis are applicable for the preparation of compounds containing important non-organic materials. A illustrative example is the preparation of the anticancer drug cisplatin from potassium tetrachloroplatinate .