Synthesis (chemistry)

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In chemistry , synthesis (from the Greek synthesis , “compilation”) describes the process in which a compound is made from elements or a complex new substance is made - sometimes also: represented - from simply built compounds . As illustration , the exemplary preparation of a compound on a laboratory scale, but also refers to the production of an element in pure form.

A synthesis is more than the (physical) mixing of two or more substances. The starting materials cannot be recovered from a newly synthesized compound through purely physical processes, in contrast to a mixture.

The raw materials used in a chemical synthesis are often referred to as reactants , reagents or obsolete as starting materials , the result as a product. The yield of the product can be influenced considerably by a suitable design of the reaction conditions such as temperature , pressure , mixing ratio , catalysts , pH value and solvent .

Types of synthesis

As a total synthesis , synonym and full synthesis or de novo synthesis is referred to the production of a natural product , without that this will fall back to intermediates derived from other sources, such. B. intermediates formed in organisms by biosynthesis . In contrast to the total synthesis is at a partial synthesis (synonym partial synthesis , more rarely, semi-synthesis ) resorted to intermediates from other sources.

The synthesis of organic compounds that takes place in living organisms is called biosynthesis.

In solid-phase synthesis, a substance is produced through a chemical reaction in which a basic molecule is chemically bound to a mostly porous polymeric carrier. The chemical changes are then carried out on this according to the following reaction scheme: reaction, washing steps with solvents to clean the bound molecule, reaction, washing steps, reaction, ..., up to the desired target molecule. This is then separated from the carrier in a reaction and, if necessary, obtained as a pure substance through further purification steps. An early example of solid phase synthesis is the Merrifield synthesis .

Technical syntheses

The most important chemical synthesis reactions are used either to produce a raw material (for example: Haber-Bosch process for the synthesis of ammonia ; production of methylchlorosilanes as an intermediate for the production of silicones ), or for the production of an active ingredient (for example: synthesis of acetylsalicylic acid from phenol ). The synthesis of chiral substances (drugs, pesticides, etc.) with a uniform three-dimensional structure can be carried out by enantioselective synthesis or enantioselective catalysis . Syntheses are often named after their discoverers, for example the Reppe synthesis , the Fischer-Tropsch synthesis or the Asinger synthesis .

See also


Individual evidence

  1. ^ Scientific review . Wissenschaftliche Verlagsgesellschaft, 1975, p. 221.
  2. ^ Brockhaus ABC Chemie, VEB FA Brockhaus Verlag Leipzig 1965, page 1370.