Assign pH to Amino Acids
Electrochemistry

Assign pH to Amino Acids


← Back to Amino Acids & Proteins

 

Approach:

 

Example 1 :

  • R–COOH is a stronger acid than R–NH3+ → pKa3 must correspond to the only –NH3+
  • –COOH closer to –NH3+ is the stronger acid

Explanation:

  • Recall factors which affects the acidity of organic compounds i.e. stability of conjugate base
  • –NH3+ is an electron withdrawing group; –COOH closer to it will form a more stable conjugate base (– COOH–) since the –ve charge the O atom will be more dispersed.

 

Example 2 :

  • R–COOH is a stronger acid than R–NH3+ → pKa1 must correspond to the only –COOH
  • –NH3+ closer to –COOH is the stronger acid

Explanation:

  • –COOH is an electron withdrawing group; –NH2 closer to –COOH will be a weaker base since its lone pairs are less available for dative bonding to H+ → corresponding –NH3+ is the stronger acid




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Electrochemistry








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