Titration of Valine by a Strong Base, for Example NaOH $\rightarrow$

Multiple Choice

Titration of valine by a strong base, for example NaOH, reveals two pK's. The titration reaction occurring at pK₂ (pK₂ = 9.62) is:

A) -COOH + OH^- $\rightarrow$ -COO^- + H₂O.
B) -COOH + -NH₂ $\rightarrow$ -COO^- + -NH₂⁺.
C) -COO^- + -NH₂⁺ $\rightarrow$ -COOH + -NH₂.
D) -NH₃⁺ + OH^- $\rightarrow$ -NH₂ + H₂O.
E) -NH₂ + OH^- $\rightarrow$ -NH^- + H₂O.