Cetrimonium bromide ((C16H33)N(CH3)3Br, cetyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, CTAB) is one of the components of the topical antiseptic cetrimide. The cetrimonium (or hexadecyltrimethylammonium) cation is an effective antiseptic agent against bacteria and fungi.
It is a cationic surfactant. Its uses include providing a buffer solution for the extraction of DNA. It has been widely used in synthesis of gold nanoparticles (e.g., spheres, rods, bipyramids). It is also widely used in hair conditioning products.
As any surfactant, it forms micelles in aqueous solutions. At 303 K (30 °C) it forms micelles with aggregation number 75-120 (depending on method of determination, usually average ~95) and degree of ionization α (fractional charge) 0.2 - 0.1 (from low to high concentration).
The standard constant of Br- counterion binding to the micelle at 303 K (30 °C) is K° ≈ 400. This value is calculated from Br- and CTA+ ion selective electrode measurements and conductometry data by using literature data for micelle size (r = ~3 nm), extrapolated to the critical micelle concentration. However, it varies with total surfactant concentration so it is extrapolated to the point at which the concentration of micelles is zero).
The closely related compounds cetrimonium chloride and cetrimonium stearate are also used as topic antiseptics, and may be found in many household products such as shampoos and cosmetics, while cetrimonium bromide, due to its high cost, is only found in select cosmetics.
Read more about Cetrimonium Bromide: Use of CTAB in Protein Electrophoresis, Genomic DNA Isolation From Plants By Modified CTAB Method