Quaternary ammonium cation

Quaternary ammonium compounds (lat. = quaternarius from each consisting fours ) occasionally QAC, quats or mistakenly called quaternary ammonium compounds are organic ammonium compounds, in which all four valences of a nitrogen atom are organically bound. It thus are salts ( ionic compounds ), consisting of a cation and an anion. There are the amine - type NR 4 X, in which all four organic radicals R, and the imine - type R = NR2 X; where X the associated anion. And N- alkylated heteroaromatic are among the quaternary ammonium compounds.

Production

Quaternary ammonium compounds are prepared by reaction of amines with alkylating agents such as methyl chloride, benzyl chloride, dimethyl sulfate, dodecyl bromide or ethylene oxide in excess.

This type of alkylation is called exhaustive alkylation.

Tertiary amines can be easily implemented on heating with alkyl halides in a quaternary amine. The reaction proceeds according to the following equation:

There are three different types of quaternary ammonium compounds and their sub- groups, namely:

• Linear alkyl ammonium compounds Alkyltrimethylammonium salts, e.g. cetyltrimethylammonium bromide
• Dialkyldi
• Benzalkonium salts, such as benzalkonium chloride
• Esterquats
• Ethoxylated QAC
• Organobentonite

Properties

Quaternary ammonium compounds are solid ionic products. You are in water easily and in many org. Solvents such as diethyl ether insoluble. They are difficult to melt and decompose when heated in the tertiary amine and the alkyl halide. With alkali to form in contrast to the hydrohalides of amines but no free amine, a stable quaternary ammonium hydroxide. This reaction is an equilibrium reaction, which is strongly shifted to Hydroxidseite. The quaternary ammonium hydroxides are strong bases comparable with sodium hydroxide and potassium hydroxide.

The quaternary ammonium hydroxides are also thermally unstable. For example decomposes the dissolved in water of tetramethylammonium hydroxide in an evaporation to trimethylamine and methanol according to the reaction equation:

This lightweight thermal cracking was noticed in 1851 by AWHofmann and used for two generally applicable methods of work:

With the first method, structure determinations were carried out by amines. Therefor all the hydrogen atoms of the amino group were first replaced by methyl groups the exhaustive methylation of the amine in question. After conversion of the resulting quaternary ammonium halide compounds in the hydroxide, the latter was thermally decomposed by pyrolysis. Depending on whether one, two or three methyl groups, had been incorporated, the corresponding primary, secondary or tertiary amines.

In the second method, the property of the quaternary ammonium compounds is used, the methyl group is significantly more bound to the amine nitrogen as alkyl groups having more carbon atoms. During pyrolysis, no alcohol is comparable to methanol formed but next trimethylamine and water and an alkene. This reaction is generally suitable for the preparation of alkenes. The reaction formula for the reaction is:

Use

QAC having at least one long alkyl group have surface active properties and can be used ( for example, in shampoos ) as cationic surfactants in products such as fabric softeners, or as invert as antistatic agents. Due to its disinfectant action they are also counted among the biocides. In public and industrial areas can be found in hospitals, food processing, agriculture, wood protection and industrial use (clean room applications). Quats are usually the main active ingredient in anti-algal agents ( algicides ) for swimming pools and pool. QACs also be used in the organic synthesis as phase transfer catalysts.

The QAC include, for example:

• Benzalkonium chloride
• Cetylpyridinium chloride
• Cetyltrimethylammonium bromide
• Denatonium benzoate
• Tetrabutylammonium hydroxide ( TBAH )
• Paraquat

QAC recently have also gained importance as the ionic liquids.

Another application for QAC is the water treatment, where they are used as a strong base ion exchange resins for the production of demineralized water. The type I of this anion exchanger is a trimethyl benzylammonium connection. The type I is more thermally stable than the exchangers of the type II, in which at least one of the three methyl groups (-N ( CH3 ) 3) of the quaternary amine by an ethyl group (-CH 2 · CH 2 · OH) has been replaced.

Biological Significance

QAC accumulate in living organisms in cell membranes and can affect the function of the cell membrane. Thanks to this effect, the cationic surfactants can also be used as disinfectants, in particular. The microbicidal effect is only achieved when the N atom bound to the alkyl group has a chain length of 8 to 18 carbon atoms. Many quaternary ammonium compounds are used in sewage treatment plants poorly eliminated and thus reach in significant quantities in the surface waters. The main sources of hospitals and laundries were identified. For this reason, lately Esterquats are increasingly being used, which can be easily dismantled.

Natural Occurrence

Choline occurs chemically bound in numerous organisms as a substance or.

Acetylcholine, acetic acid ester of choline, an important neurotransmitter.

Betaine is an oxidation product of choline and plays a role in transmethylation processes.

The fly agaric contains L-( )- muscarine, a poisonous natural substance which belongs to the class of compounds of quaternary ammonium compounds.

The occurring in plants of the genus Chondrodendron quaternary ammonium compound D- tubocurarine is part of the curare arrow poison.

The alkaloids sanguinarine, chelerythrine (eg in celandine occurring) and berberine (such as in the barberry ), due to their quaternary structure on a bright red or yellow color.

More recently, there was residue findings of QACs, especially BAC ( benzalkonium chloride ) and DDAC ( didecyldimethylammoniumchloride ) on fresh fruit and vegetables as well as in plant strengthening agents.

Nomenclature

In addition to the official IUPAC nomenclature, the trivial names of the alkyl groups are for the description of quaternary ammonium compounds with long alkyl chains, in particular, often used.

According to the IUPAC classification, the names of these compounds are derived from Azanium ion.