Tetramethylammonium chloride is a quaternary ammonium salt with the chemical formula [(CH₃)₄N]Cl. It is a very hygroscopic colourless solid that is soluble in water and polar organic solvents. Tetramethylammonium chloride has few applications, unlike quaternary ammonium salts that feature longer alkyl substituents.

Preparation and laboratory uses

Tetramethylammonium chloride can be synthesized by the alkylation

Alkylation

Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...

 of ammonium chloride

Ammonium chloride

Ammonium chloride NH4Cl is an inorganic compound with the formula NH4Cl. It is a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of natural, mineralogical form of ammonium chloride...

 with dimethyl carbonate

Dimethyl carbonate

Dimethyl carbonate, often abbreviated DMC, a carbonate ester, is a flammable clear liquid boiling at 90 °C. This compound has found use as a methylating agent and more recently as a VOC exempt solvent in paints and adhesives . There is also interest in using this compound as a fuel oxygenate...

.

[NH₄⁺]Cl⁻ + 2 (CH₃O)₂CO → [N(CH₃)₄⁺]Cl⁻ + 2 H₂O + 2 CO₂

It is used in organic synthesis for methylation and occasionally as a precipitating agent.

In low concentrations, it is used with polymerase chain reactions to increase yield and specificity. It has been shown to enhance yield 5-10 fold at 60mM by stabilizing the AT base pairs.