Question

In aqueous solution, amino acids mostly exist as:

• A. $N{H}_2-CH\left(R\right)-COOH$
• B. $N{H}_2-CH\left(R\right)-CO{O}^{-}$
• C. ${}^{+}N{H}_3-CH\left(R\right)-COOH$
• D. $\left(H_3{N}^{+}\right)-CH\left(R\right)-CO{O}^{-}$

Answer 1

The correct option is D $\left(H_3{N}^{+}\right)-CH\left(R\right)-CO{O}^{-}$

In aq. medium, The amino acids exists as Zwitterions (as shown above). These are electrically neutral species. In aq. solution the $H^{+}$ ion is transformed from one end which is $-COOH$ to $N{H}_2$ to form $COO-$ and $N{H}_3^{+}$.