See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Acidic Strength Analysis of Amino Acid Ionizable Groups **Identify the three ionizable groups:** - $x$: Carboxyl group ($COOH$) — $pK_a \approx 2.2$ - $y$: $\alpha$-amino group ($NH_3^+$) — $pK_a \approx 9.6$ - $z$: Side chain amino group ($NH_3^+$) — $pK_a \approx 10.5$ **Determine acidic strength order:** Acidic strength is inversely related to $pK_a$ — **lower $pK_a$ = stronger acid**. $$\text{Acidic strength}: x > z > y$$ This translates to: $pK_a(x) < pK_a(z) < pK_a(y)$ **Why this order?** - The **carboxyl group is most acidic** ($pK_a = 2.2$) due to resonance stabilization of its conjugate base - The **$\alpha$-amino group is least acidic** ($pK_a = 9.6$) due to its stronger basicity - The **side chain amino is intermediate** in acidity ($pK_a = 10.5$) **Answer: (D) $x > z > y$** ✓