Rubidium oxalate

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Structural formula
2 Rubidium ion Structure of the oxalate anion
General
Surname Rubidium oxalate
Molecular formula Rb 2 C 2 O 4
Brief description

colorless, dull crystals

External identifiers / databases
CAS number 7243-75-6
Wikidata Q1616359
properties
Molar mass
  • 258.97 g · mol -1 (neat)
  • 276.98 g mol −1 (monohydrate)
Physical state

firmly

density

2.76 g cm −3 (monohydrate)

Melting point

decomposition

safety instructions
GHS hazard labeling
no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Rubidium oxalate is the rubidium salt of oxalic acid .

Manufacturing

Rubidium oxalate can be made from rubidium carbonate and oxalic acid.

It is also formed during the thermal decomposition of rubidium formate .

properties

Rubidium oxalate crystallizes as monohydrate (COO) 2 Rb 2 in the monoclinic crystal system. and is isomorphic to potassium oxalate monohydrate. There are two modifications of the anhydrate at room temperature : one modification is monoclinic and isotypic to cesium oxalate , the other is orthorhombic and isotypic to potassium oxalate. Freshly produced anhydrous rubidium oxalate initially mainly contains the monoclinic phase , but this slowly converts irreversibly into the orthorhombic modification. In 2004, two more high temperature phases of rubidium oxalate were discovered. Crystal data of the various modifications of rubidium oxalate:

modification Crystal system Space group  a in Å   b in Å   c in Å   β   Z 
alpha monoclinic P2 1 / c 6.328 10.455 8.217 98.016 ° 4th
beta orthorhombic Pbam 11.288 6.295 3,622 - 2
Monohydrate monoclinic C2 / c 9.617 6.353 11.010 109.46 ° 4th

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

The decomposition of rubidium oxalate with the release of carbon monoxide and subsequently carbon dioxide and oxygen takes place at 507 - 527 ° C.

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 and forms monoclinic crystals, as well as an acidic tetraoxalate with the formula RbH 3 (COO) 4 , which crystallizes as a dihydrate, at 18 ° C has a density of 2.125 g / cm −3 and a solubility of 21 g / l at 21 ° C.

When a solution in hydrogen peroxide is evaporated, rubidium oxalate forms a monoperhydrate with the composition (COO) 2 Rb 2 · H 2 O 2 , which forms monoclinic crystals that are relatively stable in air.

Rubidium oxalate reacts with hydrogen fluoride to form a complex compound.

Individual evidence

  1. ^ A b c Jean D'Ans, Ellen Lax: Pocket book for chemists and physicists. 3. Elements, inorganic compounds and materials, minerals, volume 3. 4th edition, Springer, 1997, ISBN 978-3-540-60035-0 , pp. 686f. ( limited preview in Google Book search)
  2. ↑ a b c Dissertation: "Conformational clarification of inorganic oxo anions of carbon", Sascha Vensky, University of Stuttgart, 2004. S. 117ff. PDF
  3. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
  4. ^ E. Giglio, S. Loreti, NV Pavel: "EXAFS: A New Approach to the Structure of Micellar Aggregates" in J. Phys. Chem. , 1988 , 92 , pp. 2858-2862. doi: 10.1021 / j100321a032
  5. ^ A b T. Meisel, Z. Halmos, K. Seybold, E. Pungor: "The thermal decomposition of alkali metal formats" in Journal of Thermal Analysis and Calorimetry 1975 , 7 (1). Pp. 73-80. doi: 10.1007 / BF01911627
  6. ↑ Björn Pedersen: “The Equilibrium Hydrogen-Hydrogen Distances in the Water Molecules in Potassium and Rubidium Oxalate Monohydrates” in Acta Cryst. , 1966 , 20 , p. 412ff. doi: 10.1107 / S0365110X66000951
  7. ^ A b c R. E. Dinnebier, S. Vensky, M. Panthöfer, M. Jansen: "Crystal and molecular structures of alkali oxalates: first proof of a staggered oxalate anion in the solid state." in Inorg. Chem , 2003 , 42 (5), pp. 1499-1507. PMID 12611516 .
  8. ↑ Robert E. Dinnebier, Sascha Vensky, Martin Jansen, Jonathan C. Hanson: Crystal Structures and Topological Aspects of the High ‐ Temperature Phases and Decomposition Products of the Alkali ‐ Metal Oxalates M 2 [C 2 O 4 ] (M = K, Rb, Cs) . In: Chemistry - A European Journal . tape 11 , no. 4 , February 4, 2005, p. 1119-1129 , doi : 10.1002 / chem.200400616 .
  9. ↑ Takuya Echigo, Mitsuyoshi Kimata: The common role of water molecule and lone electron pair as a bond-valence mediator in oxalate complexes: the crystal structures of Rb 2 (C 2 O 4 ) H 2 O and Tl 2 (C 2 O 4 ) . In: Journal of Crystallography . tape 221 , no. November 12 , 2006, pp. 762–769 , doi : 10.1524 / zkri.2006.221.12.762 .
  10. ↑ Y. Masuda, H. Miyamoto, Y. Kaneko, K. Hirosawa: "The standard molar enthalpies of formation of crystalline rubidium and cesium oxalates" in J. Chem. Thermodynamics , 1985 , 17 (2), pp. 159-164 . doi: 10.1016 / 0021-9614 (85) 90068-0
  11. ↑ J. Piccard: "Contribution to the knowledge of the rubidium compounds " in Journal für Praktische Chemie 1862 , 86 (1), pp. 449-460. doi: 10.1002 / prac.18620860163 full text
  12. ^ H. Watts: "A dictionary of chemistry and the allied branches of other sciences", Volume 4, Verlag Longmans, Green and Co., 1866, p. 264. ( limited preview in the Google book search)
  13. ^ R. Abegg, F. Auerbach: "Handbuch der inorganic Chemie". Verlag S. Hirzel, Vol. 2, 1908. P. 435. Full text
  14. ↑ BF Pedersen: "The Crystal Structure of Potassium and Rubidium Oxalate Monoperhydrates, K 2 C 2 O 4 .H 2 O 2 and Rb 2 C 2 O 4 .H 2 O 2 " in Acta Chem. Scand. 1967 , 21 , pp. 779-790. doi: 10.3891 / acta.chem.scand.21-0779
  15. ↑ RF Weinland, W. Stille: "About the addition of crystalline hydrogen fluoride to oxalates and ammonium tartrate" in Justus Liebigs Annalen der Chemie 1903 , 328 (2), pp. 149-153. doi: 10.1002 / jlac.19033280205