Orthonitrate

Orthonitrate
Names
	IUPAC name Orthonitrate
Identifiers
CAS Number	54991-46-7;
3D model (JSmol)	Interactive image;
PubChem CID	potassium salt: 139047089;
	InChI InChI=1S/NO4/c2-1(3,4)5/q-3 Key: QKSQKFHZSYXUGK-UHFFFAOYSA-N;
	SMILES [N+]([O-])([O-])([O-])[O-];
Properties
Chemical formula	NO3−; 4
Molar mass	78.006
Conjugate acid	Orthonitric acid
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
	Infobox references

Orthonitrate is a tetrahedral oxoanion of nitrogen with the formula NO³⁻
₄. It was first identified in 1977[1] and is currently known in only two compounds, sodium orthonitrate (Na₃NO₄) and potassium orthonitrate (K₃NO₄). The corresponding oxoacid, orthonitric acid (H₃NO₄), is hypothetical and has never been observed. Sodium and potassium orthonitrate can be prepared by fusion of the nitrate and metal oxide under high temperatures[2] and ideally high pressures (several GPa).[3]

NaNO₃ + Na₂O → Na₃NO₄ (300 °C for 3 days)[4]

The resulting orthonitrates are white solids which are extremely sensitive to moisture and CO₂ , decomposing within minutes to sodium hydroxide, sodium carbonate, and sodium nitrate upon exposure to air.[1]

Na₃NO₄ + CO₂ → NaNO₃ + Na₂CO₃

Na₃NO₄ + H₂O → NaNO₃ + 2NaOH

The orthonitrate ion is tetrahedral with N–O bond lengths of 139 pm, which is unexpectedly short, indicating that polar interactions are shortening the bond.[4] This short bond length parallels that of oxoanions containing third-row elements like PO₄³⁻ and SO₄²⁻, for which pπ-dπ bonding was previously proposed as the explanation for the short bond length. Since 3d orbitals of nitrogen are much too high in energy to be involved in the case of orthonitrate, the shortness of the N–O bond in orthonitrate indicates that pπ-dπ bonding is likely not the most important explanation for the bond lengths of these heavier anions either.[2] (See the article on hypervalence for a discussion of bonding models)

Other nitrogen oxoanions

nitrate, NO₃⁻
nitrite, NO₂⁻

References

Jansen, Martin (August 1977). "Detection of an Orthonitrate by Vibrational Spectroscopy: Na₃NO₄". Angewandte Chemie International Edition in English. 16 (8): 534–535. doi:10.1002/anie.197705341.
Jansen, Martin (1979-08-31). "Crystal Structure of Na₃NO₄". Angewandte Chemie International Edition in English. 18 (9): 698–699. doi:10.1002/anie.197906982.
Quesada Cabrera, R.; Sella, A.; Bailey, E.; Leynaud, O.; McMillan, P.F. (April 2011). "High-pressure synthesis and structural behavior of sodium orthonitrate Na₃NO₄" (PDF). Journal of Solid State Chemistry. 184 (4): 915–920. Bibcode:2011JSSCh.184..915Q. doi:10.1016/j.jssc.2011.02.013.
Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

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[origin-1] Jansen, Martin (August 1977). "Detection of an Orthonitrate by Vibrational Spectroscopy: Na₃NO₄". Angewandte Chemie International Edition in English. 16 (8): 534–535. doi:10.1002/anie.197705341.

[:0-2] Jansen, Martin (1979-08-31). "Crystal Structure of Na₃NO₄". Angewandte Chemie International Edition in English. 18 (9): 698–699. doi:10.1002/anie.197906982.

[3] Quesada Cabrera, R.; Sella, A.; Bailey, E.; Leynaud, O.; McMillan, P.F. (April 2011). "High-pressure synthesis and structural behavior of sodium orthonitrate Na₃NO₄" (PDF). Journal of Solid State Chemistry. 184 (4): 915–920. Bibcode:2011JSSCh.184..915Q. doi:10.1016/j.jssc.2011.02.013.

[Greenwood-4] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.