NH2- vs. H-: Electronegativity and Basicity

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Discussion Overview

The discussion centers around the comparative basicity of NH2- and H-, exploring the influence of electronegativity and structural factors on their basicity. Participants examine thermodynamic data and structural considerations in the context of chemical reactions.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions why NH2- is considered a stronger base than H-, suggesting that nitrogen's greater electronegativity might imply a stronger hold on its electrons, potentially making it less basic.
  • Another participant presents thermodynamic data, indicating that the reaction involving NH2- has a more favorable Gibbs free energy change compared to the reaction involving H-, which suggests a greater equilibrium constant for NH2-.
  • Some participants express uncertainty about how to determine basicity strictly based on structural factors, with one participant stating that it may not be possible to do so.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the reasons behind the basicity differences, with ongoing debate regarding the roles of electronegativity and structural considerations.

Contextual Notes

Limitations include potential missing assumptions about the definitions of basicity and the specific structural factors that influence it. The discussion does not resolve the complexities of these relationships.

Avi_R
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Why is NH2- a stronger base than H-. I would think that due to N's greater electronegatavity, it would want to hold on to its electrons more, making it less basic.
 
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NH2- + H+ --> NH3; (delta)G reaction = -1657 Kj/mol
H- + H+ --> H2; (delta)G reaction = -1649 Kj/mol

So, the reaction NH2- + H2O --><-- NH3 + OH- has a lesser (delta)G than the reaction H- + H2O --><-- H2 + OH-; that is, the first one has a greater equilibrium constant than the second.

with --><-- I mean equilibrium reaction.
 
Thanks for the answer, but speaking strictly based on structure, how would we determine this?
 
Avi_R said:
Thanks for the answer, but speaking strictly based on structure, how would we determine this?
I don't think it's possible, at least AFAIK.
 

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