Why is nitrogen basic while oxygen and flourine are not?

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Discussion Overview

The discussion revolves around the basicity of nitrogen compared to oxygen and fluorine, exploring the reasons behind nitrogen's ability to act as a Lewis base while oxygen and fluorine do not exhibit the same behavior. Participants delve into the implications of electronegativity, lone pairs of electrons, and the reactivity of these elements in various chemical contexts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that nitrogen is a Lewis base due to its lone pair of electrons, while questioning why oxygen does not utilize its lone pairs in similar reactions.
  • Others argue that the higher electronegativity of oxygen and fluorine makes it less favorable for these atoms to share their lone pairs with electrophiles, although they acknowledge that reactions can occur under specific conditions, such as protonation of alcohols at low pH.
  • A participant mentions that fluorine is highly reactive and unstable, suggesting that it rarely exists as an ion in practical scenarios.
  • There is a discussion about the dissociation of HF, with some participants noting its weak acidity and relatively high pKa compared to other halides, while others express uncertainty about its dissociation in solution.
  • One participant challenges the notion that oxygen does not react with electrophiles, citing examples of stable adducts and reactions involving electrophiles like H+ and BF3.
  • Clarifications are made regarding the spelling of "fluorine," indicating attention to detail in chemical terminology.

Areas of Agreement / Disagreement

Participants express differing views on the reactivity and basicity of nitrogen, oxygen, and fluorine, with no consensus reached on the reasons behind these differences. The discussion remains unresolved regarding the extent of oxygen's reactivity and the behavior of fluorine in solution.

Contextual Notes

Some claims depend on specific conditions, such as pH levels for protonation reactions, and the discussion includes unresolved questions about the stability of adducts and the behavior of ions in solution.

CrimpJiggler
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Nitrogen is a lewis base because it has a lone pair of electrons with which to form bonds with electrophiles. Oxygen has 2 lone pairs of electrons and halogens have 3. Why doesn't oxygen use any of its spare pairs of electrons to react with electrophiles?
 
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Oxygen and fluorine are more electronegative than nitrogen, so it is less favorable for these atoms to share their lone pairs with an electrophile. This is not to say that it is impossible, for example, alcohols get protonated at very low pH (around -1 to -2).
 
I want to say that Flourine is waaaaaaaaaay too reactive / unstable. . . it never exists as an ion irl.
 
Ygggdrasil: that explains it, thanks.

Highway: So the F- ion is uncommon is it? I've read that HF is a weak acid but I don't know what its dissociation constant. Are you saying that HF doesn't actually dissociate at all?
 
CrimpJiggler said:
Ygggdrasil: that explains it, thanks.

Highway: So the F- ion is uncommon is it? I've read that HF is a weak acid but I don't know what its dissociation constant. Are you saying that HF doesn't actually dissociate at all?
HF is a very strongly reactive acid that can break down lots of oxides and can etch glass.
 
HF has a pKa of 3.17. Compared to the other halides (e.g. HCl pKa ~ -7, HBr pKa ~ -9), this is quite a high value. So, HF will dissociate, but not to the same extent as related compounds.
 
CrimpJiggler said:
Nitrogen is a lewis base because it has a lone pair of electrons with which to form bonds with electrophiles. Oxygen has 2 lone pairs of electrons and halogens have 3. Why doesn't oxygen use any of its spare pairs of electrons to react with electrophiles?

Who sais so? H+ is quite electrophilic and readily reacts with H2O to form hydronium ions H3O+ and also FH2- forms stable salts. Other electrophiles? I think there are adducts of BF3 and various ethers. And of course you can make all kinds of electrophilic substitutions on oxygen. So its more a question of stability of the adducts with respect to further reactions. Finally there are salts like trimethyloxonium tetrafluoroborate (Meerwein salt).

Btw. its fluorine, not flourine.
 
CrimpJiggler said:
Ygggdrasil: that explains it, thanks.

Highway: So the F- ion is uncommon is it? I've read that HF is a weak acid but I don't know what its dissociation constant. Are you saying that HF doesn't actually dissociate at all?

I remember this coming up in class and our prof saying that F- exists for only a very short time in solution, due to it's high reactivity.

Email your prof the same question -- he'll give you a better answer than I can, as I'm not a chemist.
 

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