Quaternization

Quadruple organically substituted compound (R = organyl group ) with central atom ( Y  = nitrogen or phosphorus ).

In chemistry, quaternization describes the conversion of suitable atoms into the quaternary degree of substitution with four organic radicals . The quaternization is thus a subgroup of the alkylations , through which a certain product class is created. Here the central atom receives four identical or different organic substituents and a positive charge - a cation is thus formed. Haloalkanes or dimethyl sulfate are used as alkylating agents ; the counterion (anion) is then a halide , e.g. B. chloride , bromide , iodide , or sulfate or methyl sulfate .

Examples

Conversion of amines to quaternary ammonium compounds

The quaternization of tertiary amines to quaternary ammonium compounds is shown using the alkylation of a tertiary amine (R = organyl group, e.g. alkyl group):

Quaternization of amines	Quaternization with spatially drawn p orbital

If you start from a primary amine (= alkylamine) and this is reacted in stages with excess haloalkane , the intermediate products are obtained

• secondary amine (= dialkylamine ) and
• tertiary amine (= trialkylamine )

analogous to a quaternary ammonium halide. The reaction of trimethylamine with iodomethane produces tetramethylammonium iodide:

${\displaystyle \mathrm {(CH_{3})_{3}N\ +\ CH_{3}I\ \longrightarrow \ (CH_{3})_{4}N^{+}\ +\ I^{-}} }$

Similarly, when trimethylamine is reacted with bromomethane, tetramethylammonium bromide is formed:

${\displaystyle \mathrm {(CH_{3})_{3}N\ +\ CH_{3}Br\ \longrightarrow \ (CH_{3})_{4}N^{+}\ +\ Br^{-}} }$

The simplest quaternary ammonium compound is tetramethylammonium chloride .

Conversion of pyridine to pyridinium compounds

An example of a quaternization is the reaction of pyridine to a pyridinium compound (R = organyl group, e.g. alkyl group):

Quaternization of pyridine	Quaternization with spatially drawn p orbital

Conversion of phosphines to phosphonium salts

The reaction of a phosphine to a quaternary phosphonium compound is also called quaternization (R = organyl group, e.g. alkyl group):

Quaternization of Phosphanes	Quaternization with spatially drawn p orbital

As an alkylating agent, a haloalkane - z. B. Bromomethane - are used; this gives a phosphonium bromide.

See also

• Alkylation
• quaternary

Individual evidence

1. ↑ ^{a b c d} Jürgen Falbe , Manfred Regitz : Römpp-Chemie-Lexikon . 9th edition. Thieme, Stuttgart 1992, ISBN 3-13-735009-3 , p. 3736 .
2. ↑ Joachim Buddrus, Bernd Schmidt: Fundamentals of Organic Chemistry , 5th Edition, de Gruyter Verlag, Berlin 2015, ISBN 978-3-11-030559-3 , p. 675.
3. ↑ Joachim Buddrus, Bernd Schmidt: Basics of Organic Chemistry , 5th edition, de Gruyter Verlag, Berlin 2015, ISBN 978-3-11-030559-3 , p. 493.