metalresearcher
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Why is there no such thing as H3NO4 ?
There is phosphoric acid H3PO4, arsenic acid H3AsO4, both from the same group as nitrogen and in oxidation state +5.
There is N2O5 and HNO3,like P2O5 and HPO3, but adding water does not make the fictional acid H3NO4.
Why ?
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Sigmatropic
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The term to look for is ortho nitrate, similar to ortho esters in naming. https://en.m.wikipedia.org/wiki/Orthonitrate
Interesting question, I'm curious for the theoretical explanation. My guess is it involves thermodynamics and the high stability of nitrate.
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fusso
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Now I wonder why is H3PO4 stable but HPO3 and its salts don't exist.
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DraconicAcid
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Nitrate is stabilized by three sigma bonds and a pi bond. Pi bonds between oxygen and phosphorus are much weaker than N-O pi bonds (the orbitals
don't match in size, so they don't overlap as well), so phosphorus would much rather have four sigma bonds instead.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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fusso
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Then why don't P go full sigma and prefer P(OH)5?
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DraconicAcid
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Then it would have to use its d orbitals in its hybridization, and those are pretty high energy.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Keras
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Quote: Originally posted by metalresearcher  | There is phosphoric acid H3PO4, arsenic acid H3AsO4, both from the same group as nitrogen and in oxidation state +5.
There is N2O5 and HNO3,like P2O5 and HPO3, but adding water does not make the fictional acid H3NO4.
Why ? |
In H₃PO₄, the central P has five bonds. N cannot do that, because N has no d orbitals (not even vacant ones – they physically don't exist at
all), therefore it is limited to 4 bonds only, much like carbon, oxygen and boron. The ability to hybridise d orbitals comes with the third row.
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DraconicAcid
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| Quote: Originally posted by Keras |
In H₃PO₄, the central P has five bonds. N cannot do that, because N has no d orbitals (not even vacant ones – they physically don't exist at
all), therefore it is limited to 4 bonds only, much like carbon, oxygen and boron. The ability to hybridise d orbitals comes with the third row.
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Nitrogen does have d orbitals, just not in the valence shell (all atoms have an infinite number of shells- even lowly hydrogen has higher shells, and
transitions from the seventh shell can be seen in its emission spectrum).
Nitrogen could conceivably form H3NO4 without a double bond to one of the oxygens (and thus only having four bonds), in a similar bonding arrangement
as in trimethylamine N-oxide (https://en.wikipedia.org/wiki/Trimethylamine_N-oxide ), but that just isn't stable.
As an aside, the conjugate base of H3NO4 has been made: https://en.wikipedia.org/wiki/Orthonitrate
[Edited on 1-10-2019 by DraconicAcid]
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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