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Encyclopedia > Phase transfer catalyst

A phase transfer catalyst or PTC in chemistry is a type of chemical compound, often a quaternary ammonium salt, which facilitates the migration of a particular chemical component in one phase into a other phase in a heterogeneous system. The chemical component is soluble in one phase but insoluble in the other unless the phase transfer catalyst is present. For example the nucleophilic aliphatic substitution reaction of an aqueous sodium cyanide solution with the alkyl halide 1-bromobutene does not ordinarily take place because both solutions will not mix. By the addition of 1% of the quaternary ammonium salt tetrahexylammonium chloride however cyanide ions are ferried into the organic phase from the water phase and 1-cyanobutane forms quantitatively in a matter of minutes. A PTC works by encapsulating the ion. The PTC-ion system has a hydrophilic interior containing the ion and a hydrophobic exterior. Crown ethers are also efficient phase transfer catalysts. // Introduction The fundamental component of chemistry is that it involves matter in some way (this explains its broad reach). ... A chemical compound is a chemical substance formed from two or more elements, with a fixed ratio determining the composition. ... Quaternary ammonium cation. ... Look up Heterogeneous in Wiktionary, the free dictionary A heterogeneous compound, mixture, or other such object is one that consists of many different items, which are often not easily sorted or separated, though they are clearly distinct. ... It has been suggested that this article or section be merged with Solution. ... In chemistry, nucleophilic substitution is a class of substitution reaction in which an electron-rich nucleophile attacks a molecule and replaces a group or atom, called the leaving group. ... Drinking water This article focuses on water as we experience it every day. ... Sodium cyanide is a highly toxic chemical compound, also known as sodium salt of hydrocyanic acid and cyanogran. ... In chemistry, an alkyl halide is an organic molecule of the form R_X, where X is a halide and R contains a carbon atom bonded to other functional groups or hydrogens. ... Quaternary ammonium cation. ... A cyanide is any chemical compound that contains the group C≡N, with the carbon atom triple-bonded to the nitrogen atom. ... ... The adjective hydrophilic describes something that likes water (from Greek hydros = water; philos = friend). ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ... Crown ethers are heterocyclic chemical compounds that, in their simplest form, are cyclic oligomers of dioxane. ...


For an explanation of how phase transfer cataylisis works see Liquid-liquid extraction for details. In chemistry, liquid-liquid extraction is a useful method to separate components (compounds) of a mixture. ...


References

  • The Sachem phase transfer catalyst review

  Results from FactBites:
 
Conversion of amides to isocyanates via phase transfer catalysis - Patent 4282167 (2687 words)
Phase transfer catalysis is a relatively recent technique which has been employed in a number of organic reactions which proceed via displacement of a leaving group by a nucleophile.
Phase transfer catalysis utilizing a quaternary salt (e.g., ammonium, phosphonium or arsonium) as the phase transfer catalyst (i.e.
Phase transfer catalysts useful in the invention are quaternary salts having the formula: ##STR2## wherein the total number of carbon atoms in R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is sufficient to render the catalyst soluble in both the organic and aqueous phases and wherein Q is nitrogen, phosphorous or arsenic.
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