organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, ...

, the High Dilution Principle is a strategy for some macrocyclization reactions, i.e. the synthesis of

macrocycle Macrocycles are often described as molecules and ions containing a ring of twelve or more atoms. Classical examples include the crown ethers, calixarenes, porphyrins, and cyclodextrins. Macrocycles describe a large, mature area of chemistry. ...

s. Unlike the synthesis of 5- and 6-membered rings, the preparation of larger rings competes unfavorably with polymerization reactions.

Polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

s arise from coupling of long chain precursors. Such reactions are disfavored when the acyclic compounds are dilute.{{cite journal, title=Synthesis of medio- and macrocyclic compounds by high dilution principle techniques, authors=Ludovica Rossa, Fritz Vögtle, journal=Topics in Current Chemistry, year=1983, volume=113 , pages=1–86 , doi=10.1007/3-540-12397-0_1, isbn=978-3-540-12397-2 Although high dilution reactions can be conducted in a batch reactor with large volumes of

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

, a more practical implementation entails slow addition of reactants, under conditions that the reactants are more rapidly consumed than the rate of addition. Typically, additions use one or more

syringe pump A syringe driver, also known as a syringe pump, is a small infusion pump, used to gradually administer small amounts of fluid (with or without medication) to a patient or for use in chemical and biomedical research. Some syringe drivers can both ...

s. Illustrative is the synthesis of thiacyclopentadecane from 1,14-dibromotetradecane and sodium sulfide in 45% yield: :BrCH₂(CH₂)₁₂CH₂Br + Na₂S → (CH₂)₁₄S + 2 NaBr

References

Carbon-carbon bond forming reactions