# Are amines amphoteric?

An amine can react with an acid just like any other base to form a salt:

$$\ce{RNH2 + HCl-> RNH3+ Cl-}$$

According to my textbook (unreliable), amines also react with bases just like any other acid:

$$\ce{RNH2 + NaOH -> RNH- Na+}$$

Do amines (if not all amines, at least the ones substituted with a strong withdrawing group) react with bases as shown in the above reaction?

In other words: Are amines amphoteric?

• One easy way to verify the second reaction is to check if SA + SB -> WA + WB condition is satisfied. Here in the second reaction one of the products is $\ce{H2O}$ which is more acidic than $\ce{RNH2}$. So the forward reaction isn't feasible. – user38977 May 6 '17 at 4:06
• This makes for a good read: www2.chemistry.msu.edu/faculty/reusch/virttxtjml/chapt16.htm – paracetamol May 6 '17 at 5:55
• Their acidity is quite low and only very strong bases, like $\ce{CH3-}$ or $\ce{N^{3-}}$ can deprotonate amines. – Pritt says Reinstate Monica May 6 '17 at 6:11
• Certainly $\ce{NaOH}$ isnt strong enough to deprotonate it, so that doesnr happen. – Pritt says Reinstate Monica May 6 '17 at 6:18
• @NilayGhosh I believe that's incorrect. Zwitterions hve two functional groups, one acidic and one basic, and have both positive and negative charges at the same time within the ion. An amine cannot be a zwitterion. – Pritt says Reinstate Monica May 6 '17 at 6:20

The typical $\mathrm pK_\mathrm a$ of an amine is $\sim 30$ (see Evans pKa table) and that of $\ce{H2O}$ is $\sim 15$. The equilibrium constant for the second equation you wrote is therefore on the order of $10^{-15}$.
Back to the question whether amines are amphoteric: If your definition of an amphoteric compound is simply "can react either as an acid or a base", then yes, it technically is, since it reacts both with acids ($\ce{HCl}$) or bases ($\ce{RLi}$).
However, it may be useful to draw the line at reacting with aqueous acid and aqueous base. Otherwise, nearly everything with a hydrogen can be considered to be amphoteric (for example, $\ce{HF}$ can technically act as a base to form $\ce{H2F+}$). Under this definition amines are not amphoteric.