Rubidium oxalate

Rubidium oxalate
Identifiers
CAS Number	10010-65-8 anhydrous ; 7243-75-6 monohydrate ;
3D model (JSmol)	Interactive image;
ChemSpider	10760835;
PubChem CID	13955568;
	InChI InChI=1S/C2H2O4.2Rb/c3-1(4)2(5)6;;/h(H,3,4)(H,5,6);;/q;2*+1/p-2 Key: DUXDETQJUQZYEX-UHFFFAOYSA-L;
	SMILES [Rb+].[O-]C(=O)C(=O)[O-].[Rb+];
Properties
Chemical formula	C2O4Rb2
Molar mass	258.954 g·mol−1
Appearance	colourless crystals
Density	2.76 g·cm−3 (monohydrate)
Related compounds
Other anions	rubidium carbonate; rubidium acetate
Other cations	lithium oxalate; sodium oxalate; potassium oxalate; caesium oxalate
Related compounds	rubidium hydroxide; oxalic acid
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Rubidium oxalate is the oxalate salt of rubidium, with the chemical formula of Rb₂C₂O₄.

Preparation

Rubidium carbonate and oxalic acid react to form rubidium oxalate:[1]

\mathrm {Rb_{2}CO_{3}+(COOH)_{2}\longrightarrow Rb_{2}(COO)_{2}+H_{2}O+CO_{2}\uparrow }

Rubidium oxalate can also be obtained via the thermal decomposition of rubidium formate:[2]

\mathrm {2\ HCOORb\ {\xrightarrow {\ \Delta \ }}\ \ (COO)_{2}Rb_{2}+H_{2}\uparrow }

Properties

Rubidium oxalate crystallizes as the monohydrate (COO)₂Rb₂ in the monoclinic crystal system.[3] and is isomorphic to potassium oxalate monohydrate.[4] Two modifications of the anhydrous form exist at room temperature: one modification is monoclinic and isotypic to caesium oxalate, the other is orthorhombic and isotypic to potassium oxalate.[5] Freshly prepared anhydrous rubidium oxalate initially contains mainly the monoclinic phase, but this slowly transforms irreversibly into the orthorhombic modification.[6] In 2004, two more high-temperature phases of rubidium oxalate were discovered.[7]

Crystal data of the different modifications of rubidium oxalate

Modification	Crystal system	Space group	a in Å	b in Å	c in Å	β	Z
Alpha[5]	monoclinic	P2₁/c	6.328	10.455	8.217	98.016°	4
Beta[5]	orthorhombisch	Pbam	11.288	6.295	3.622	—	2
Monohydrate[8]	monoclinic	C2/c	9.617	6.353	11.010	109.46°	4

The standard enthalpy of formation of the crystalline rubidium oxalate is 1325.0 ± 8.1 kJ/mol.[9]

The decomposition of rubidium oxalate with the release of carbon monoxide and subsequently carbon dioxide and oxygen takes place at 507–527 °C.[6][2]

\mathrm {(COO)_{2}Rb_{2}\ {\xrightarrow {\ \Delta \ }}\ \ Rb_{2}CO_{3}+CO\uparrow }

\mathrm {Rb_{2}CO_{3}\ {\xrightarrow {\ \Delta \ }}\ \ Rb_{2}O+CO_{2}\uparrow }

\mathrm {2\ Rb_{2}O\ {\xrightarrow {\ \Delta \ }}\ \ 4\ Rb+O_{2}\uparrow }

In addition to the neutral rubidium oxalate, there is also a hydrogen oxalate with the formula RbH(COO)₂, which is isomorphic to the corresponding potassium compound[10] and forms monoclinic crystals,[11] and an acidic tetraoxalate with the formula RbH₃(COO)₄, which exists as a dihydrate, has a density of 2.125 g/cm₃ at 18 °C and a solubility of 21 g/L at 21 °C.[12]

Upon evaporation of a solution in hydrogen peroxide, rubidium oxalate forms a monoperhydrate of the composition (COO)₂Rb₂·H₂O₂, which forms monoclinic crystals that are relatively stable in air.[13]

Rubidium oxalate reacts with hydrogen fluoride to form a complex compound:[14]

\mathrm {(COO)_{2}Rb_{2}+2HF\ \longrightarrow \ \ (COO)_{2}HRb\cdot HF+RbF}

References

Giglio, E.; Loreti, S.; Pavel, N. V. (May 1988). "EXAFS: a new approach to the structure of micellar aggregates". The Journal of Physical Chemistry. 92 (10): 2858–2862. doi:10.1021/j100321a032. ISSN 0022-3654.
Meisel, T.; Halmos, Z.; Seybold, K.; Pungor, E. (February 1975). "The thermal decomposition of alkali metal formates". Journal of Thermal Analysis. 7 (1): 73–80. doi:10.1007/BF01911627. ISSN 0022-5215. S2CID 93705025.
Ans, Jean d'; Lax, Ellen (1998). Taschenbuch für Chemiker und Physiker (in German). Springer. ISBN 978-3-540-60035-0.
Pedersen, B. (1966-03-01). "The equilibrium hydrogen–hydrogen distances in the water molecules in potassium and rubidium oxalate monohydrates". Acta Crystallographica. 20 (3): 412–417. doi:10.1107/S0365110X66000951. ISSN 0365-110X.
Dinnebier, Robert E.; Vensky, Sascha; Panthöfer, Martin; Jansen, Martin (2003-03-10). "Crystal and molecular structures of alkali oxalates: first proof of a staggered oxalate anion in the solid state". Inorganic Chemistry. 42 (5): 1499–1507. doi:10.1021/ic0205536. ISSN 0020-1669. PMID 12611516.
Vensky, Sascha (2004). Konformationsaufklärung anorganischer Oxoanionen des Kohlenstoffs und Festkörpersynthesen durch Elektrokristallisation von Ag3O4 und Na3BiO4 (doctoralThesis thesis) (in German).
Robert E. Dinnebier, Sascha Vensky, Martin Jansen, Jonathan C. Hanson (2005-02-04), "Crystal Structures and Topological Aspects of the High-Temperature Phases and Decomposition Products of the Alkali-Metal Oxalates M₂[C₂O₄] (M=K, Rb, Cs)", Chemistry - A European Journal, vol. 11, no. 4, pp. 1119–1129, doi:10.1002/chem.200400616, PMID 15624128{{citation}}: CS1 maint: multiple names: authors list (link)
Takuya Echigo, Mitsuyoshi Kimata (November 2006), "The common role of water molecule and lone electron pair as a bond-valence mediator in oxalate complexes : the crystal structures of Rb₂(C₂O₄) · H₂O and Tl₂(C₂O₄)", Zeitschrift für Kristallographie, vol. 221, no. 12, pp. 762–769, Bibcode:2006ZK....221..762E, doi:10.1524/zkri.2006.221.12.762, S2CID 98482669
Masuda, Y.; Miyamoto, H.; Kaneko, Y.; Hirosawa, K. (February 1985). "The standard molar enthalpies of formation of crystalline rubidium and cesium oxalates". The Journal of Chemical Thermodynamics. 17 (2): 159–164. doi:10.1016/0021-9614(85)90068-0.
Piccard, Julius (1862). "Beitrag zur Kenntniss der Rubidiumverbindungen". Journal für Praktische Chemie (in German). 86 (1): 449–460. doi:10.1002/prac.18620860163. ISSN 0021-8383.
Watts, Henry (1866). A Dictionary of Chemistry and the Allied Branches of Other Sciences. Longmans, Green, Longman, Roberts & Green.
Abegg, Richard Wilhelm Heinrich; Auerbach, Friedrich; Koppel, Ivan (1905). Handbuch der anorganischen Chemie. University of California. Leipzig, S. Hirzel.
Pedersen, Berit F.; Seip, Hans M.; Santesson, Johan; Holmberg, Pär; Eriksson, G.; Blinc, R.; Paušak, S.; Ehrenberg, L.; Dumanović, J. (1967). "The Crystal Structure of Potassium and Rubidium Oxalate Monoperhydrates, K2C2O4.H2O2 and Rb2C2O4.H2O2". Acta Chemica Scandinavica. 21: 779–790. doi:10.3891/acta.chem.scand.21-0779. ISSN 0904-213X.
Weinland, R. F.; Stille, W. (1903). "Ueber die Anlagerung von Krystallfluorwasserstoff an Oxalate und an Ammoniumtartrat". Justus Liebig's Annalen der Chemie (in German). 328 (2): 149–153. doi:10.1002/jlac.19033280205.

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[1] Giglio, E.; Loreti, S.; Pavel, N. V. (May 1988). "EXAFS: a new approach to the structure of micellar aggregates". The Journal of Physical Chemistry. 92 (10): 2858–2862. doi:10.1021/j100321a032. ISSN 0022-3654.

[Miesel-2] Meisel, T.; Halmos, Z.; Seybold, K.; Pungor, E. (February 1975). "The thermal decomposition of alkali metal formates". Journal of Thermal Analysis. 7 (1): 73–80. doi:10.1007/BF01911627. ISSN 0022-5215. S2CID 93705025.

[3] Ans, Jean d'; Lax, Ellen (1998). Taschenbuch für Chemiker und Physiker (in German). Springer. ISBN 978-3-540-60035-0.

[4] Pedersen, B. (1966-03-01). "The equilibrium hydrogen–hydrogen distances in the water molecules in potassium and rubidium oxalate monohydrates". Acta Crystallographica. 20 (3): 412–417. doi:10.1107/S0365110X66000951. ISSN 0365-110X.

[Dinnebier-5] Dinnebier, Robert E.; Vensky, Sascha; Panthöfer, Martin; Jansen, Martin (2003-03-10). "Crystal and molecular structures of alkali oxalates: first proof of a staggered oxalate anion in the solid state". Inorganic Chemistry. 42 (5): 1499–1507. doi:10.1021/ic0205536. ISSN 0020-1669. PMID 12611516.

[Vensky-6] Vensky, Sascha (2004). Konformationsaufklärung anorganischer Oxoanionen des Kohlenstoffs und Festkörpersynthesen durch Elektrokristallisation von Ag3O4 und Na3BiO4 (doctoralThesis thesis) (in German).

[Dinnebier1-7] Robert E. Dinnebier, Sascha Vensky, Martin Jansen, Jonathan C. Hanson (2005-02-04), "Crystal Structures and Topological Aspects of the High-Temperature Phases and Decomposition Products of the Alkali-Metal Oxalates M₂[C₂O₄] (M=K, Rb, Cs)", Chemistry - A European Journal, vol. 11, no. 4, pp. 1119–1129, doi:10.1002/chem.200400616, PMID 15624128{{citation}}: CS1 maint: multiple names: authors list (link)

[Echigo-8] Takuya Echigo, Mitsuyoshi Kimata (November 2006), "The common role of water molecule and lone electron pair as a bond-valence mediator in oxalate complexes : the crystal structures of Rb₂(C₂O₄) · H₂O and Tl₂(C₂O₄)", Zeitschrift für Kristallographie, vol. 221, no. 12, pp. 762–769, Bibcode:2006ZK....221..762E, doi:10.1524/zkri.2006.221.12.762, S2CID 98482669

[9] Masuda, Y.; Miyamoto, H.; Kaneko, Y.; Hirosawa, K. (February 1985). "The standard molar enthalpies of formation of crystalline rubidium and cesium oxalates". The Journal of Chemical Thermodynamics. 17 (2): 159–164. doi:10.1016/0021-9614(85)90068-0.

[Piccard-10] Piccard, Julius (1862). "Beitrag zur Kenntniss der Rubidiumverbindungen". Journal für Praktische Chemie (in German). 86 (1): 449–460. doi:10.1002/prac.18620860163. ISSN 0021-8383.

[Watts-11] Watts, Henry (1866). A Dictionary of Chemistry and the Allied Branches of Other Sciences. Longmans, Green, Longman, Roberts & Green.

[Abegg-12] Abegg, Richard Wilhelm Heinrich; Auerbach, Friedrich; Koppel, Ivan (1905). Handbuch der anorganischen Chemie. University of California. Leipzig, S. Hirzel.

[13] Pedersen, Berit F.; Seip, Hans M.; Santesson, Johan; Holmberg, Pär; Eriksson, G.; Blinc, R.; Paušak, S.; Ehrenberg, L.; Dumanović, J. (1967). "The Crystal Structure of Potassium and Rubidium Oxalate Monoperhydrates, K2C2O4.H2O2 and Rb2C2O4.H2O2". Acta Chemica Scandinavica. 21: 779–790. doi:10.3891/acta.chem.scand.21-0779. ISSN 0904-213X.

[14] Weinland, R. F.; Stille, W. (1903). "Ueber die Anlagerung von Krystallfluorwasserstoff an Oxalate und an Ammoniumtartrat". Justus Liebig's Annalen der Chemie (in German). 328 (2): 149–153. doi:10.1002/jlac.19033280205.