Common types of amphoteric surfactants

For ease of reference, the four basic classes are referred to throughout this book as WW, WS, SW and SS amphoterics, where W means weak and S strong, and the first letter refers to the acid group and the second to the basic group. This is the author s own convention and is not generally recognised. 

Carboxylates with weakly basic N (WW). Structures shown are of the zwitterionic, i.e. internally neutralised, forms. These gain a proton in acid solution to give the fully protonated (cationic) form, electrically neutralised by the anion of the acid. They lose a proton in alkaline solution to give the fully deprotonated (anionic) form, electrically neutralised by the cation of the base. 

Imidazoline derivatives are sometimes shown as ring structures. This is now generally thought to be incorrect ring opening occurs during synthesis and the products are derivatives of a monoamide of ethylene diamine, as shown here. 

Carboxylates with strongly basic N (WS), These are also shown as zwitterions. They gain a proton in acid solution to give the fully protonated (cationic) form, but cannot lose a proton. 

---