Question

Among the following, the surfactant that will form micelles in aqueous solution at the lowest molar concentration at ambient condition is:

• A. $C{H}_3\left(C{H}_2{)}_{15}{N}^{+}\right(C{H}_3{)}_{3}B{r}^{-}$
• B. $C{H}_3(C{H}_2{)}_{11}OS{O}_3^{-}N{a}^{+}$
• C. $C{H}_3(C{H}_2{)}_{6}CO{O}^{-}N{a}^{+}$
• D. $C{H}_3\left(C{H}_2{)}_{11}{N}^{+}\right(C{H}_3{)}_{3}B{r}^{-}$

Answer 1

The correct option is A $C{H}_3\left(C{H}_2{)}_{15}{N}^{+}\right(C{H}_3{)}_{3}B{r}^{-}$

In colloidal, critical micelle concentration (CMC) is the concentration of surfactants above which micelles form and all additional surfactants added to the system go to micelles. CMC depends on chain length (hydrophobic part). Longer the hydrophobic part of the molecule easy will be the formation of micelle. Among all, $C{H}_3\left(C{H}_2{)}_{15}{N}^{+}\right(C{H}_3{)}_{3}B{r}^{-}$ has the longest carbon chain. So, it has the lowest CMC.