Cetyltrimethylammonium

Cetyltrimethylammonium refers to the cetyltrimethylammonium cation, a quaternary ammonium ion composed of a cetyl (C16) alkyl chain attached to a permanently positively charged nitrogen atom. In practice, this cation is encountered most often as salts such as cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC), among other anions.

The molecule is amphiphilic: the long hydrophobic tail and the positively charged hydrophilic head give it surfactant properties. It forms micelles in aqueous solution above its critical micelle concentration, which is typically around 0.9 to 1.0 millimolar at room temperature, though the exact value depends on temperature and ionic strength. The cationic headgroup enables strong interactions with negatively charged surfaces, including many biomolecules and cell membranes.

Applications of cetyltrimethylammonium salts are broad. They are widely used as cationic surfactants in household and personal care products, including shampoos and cleaners, and as antimicrobial and conditioning agents. In molecular biology and biochemistry, CTAB is well known for its role in DNA extraction protocols (the CTAB method), particularly for plant tissues where it helps purify nucleic acids by complexing polysaccharides. In materials science, cetyltrimethylammonium salts act as structure-directing agents in the synthesis of mesoporous silica materials and related catalysts.

Safety and environmental considerations are important. Cetyltrimethylammonium salts can be irritants and may be toxic to aquatic organisms; they are not always readily biodegradable. Proper handling, ventilation, and waste management, along with adherence to regulatory guidelines, are advised in industrial and laboratory settings.