Amino Acid Titration: Why COOH H First?

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    Acid Titration
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Discussion Overview

The discussion revolves around the titration of amino acids with strong bases, specifically addressing why the hydrogen from the carboxyl (COOH) group is removed before that from the amino (NH3+) group. Participants explore the underlying reasons for this sequence in terms of acidity and molecular interactions.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the order of hydrogen removal during titration, suggesting that the repulsion from the NH3+ group might influence the carboxyl hydrogen being removed first.
  • Another participant asks which group is typically the stronger acid, COOH or NH3+, indicating a need for clarification on their relative acid strengths.
  • A follow-up response reiterates the question about the acid strength of COOH compared to NH3+, expressing uncertainty about NH3+ acting as a weak acid or a base.
  • A later reply clarifies that -NH2 is a base and -NH3+ is a conjugate acid, contributing to the discussion on acid-base behavior.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the reasons behind the order of hydrogen removal, and multiple competing views regarding the acid strengths of COOH and NH3+ remain unresolved.

Contextual Notes

The discussion highlights assumptions about acid strength and the influence of molecular structure on titration behavior, but these aspects are not fully resolved or defined.

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Homework Statement


Lets say we titrate an amino acid with a strong base (NaOH), like I know that the hydrogen of the carboxyl (COOH) group will be pulled away followed by the amino group (NH3+), but is there a particular reason why the hydrogen on the carboxyl group is pulled out first rather than the amino acid? Does it have to do with the repulsion caused by the NH3+ group that causes the carboxyl hydrogen to come off first?
Thanks.


Homework Equations





The Attempt at a Solution

 
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Which is usually a stronger acid - -COOH, or -NH3+?
 
Borek said:
Which is usually a stronger acid - -COOH, or -NH3+?
Is COOH the stronger acid? but then NH3+ is a weak acid? (i somehow thought that NH3+ acts as a base...)
 
-NH2 is a base, -NH3+ is a conjugate acid.

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