Rubidium chloride
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| Rubidium chloride | |
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| Other names rubidium(I) chloride | |
| Identifiers | |
| CAS number | 7791-11-9  |
| PubChem | 62683 |
| ChemSpider | 56434 |
| RTECS number | VL8575000 |
| Jmol-3D images | {{#if:[Rb+].[Cl-]|Image 1 |
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| Properties | |
| Molecular formula | RbCl |
| Molar mass | 120.921 g/mol |
| Appearance | white crystals hygroscopic |
| Density | 2.80 g/cm3 (25 °C) 2.088 g/mL (750 °C) |
| Melting point | 718 °C |
| Boiling point | 1390 °C |
| Solubility in water | 77 g/100mL (0 °C) 91 g/100 mL (20 °C) 130 g/100 mL (100 °C) |
| Solubility in methanol | 1.41 g/100 mL |
| Refractive index (nD) | 1.5322 |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
−435.14 kJ/mol |
| Standard molar entropy S |
95.9 J K−1 mol−1 |
| Specific heat capacity, C | 52.4 J K−1 mol−1 |
| Hazards | |
| MSDS | Fisher Scientific |
| EU Index | Not listed |
| NFPA 704 |
 0
1
0
|
| Flash point | Non-flammable |
| LD50 | 4440 mg/kg (rat) |
| Related compounds | |
| Other anions | Rubidium fluoride Rubidium bromide Rubidium iodide |
| Other cations | Lithium chloride Sodium chloride Potassium chloride Caesium chloride |
(verify) (what is: / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa) | |
| Infobox references | |
Rubidium chloride is the alkali metal halide RbCl. This alkali halide finds diverse uses, from electrochemistry to molecular biology.
Structure
In its gas phase, RbCl is diatomic with a bond length estimated at 2.7868 Å.[1] This distance increases to 3.285 Å for cubic RbCl, reflecting the higher coordination number of the ions in the solid phase.[2]
Depending on conditions, solid RbCl exists in one of three arrangements or polymorphs as determined with holographic imaging:[3]
Sodium chloride (octahedral 6:6)
The NaCl polymorph is most common. A cubic close-packed arrangement of chloride anions with rubidium cations filling the octahedral holes describes this polymorph.[4] Both ions are six-coordinate in this arrangement. This polymorph's lattice energy is only 3.2 kJ/mol less than the following structure's.[5]
Caesium chloride (cubic 8:8)
At high temperature and pressure, RbCl adopts the CsCl structure (NaCl and KCl undergo the same structural change at high pressures). Here, the chloride ions form a simple cubic arrangement with chloride anions occupying the vertices of a cube surrounding a central Rb+. This is RbCl's densest packing motif.[2] Because a cube has eight vertices, both ions' coordination numbers equal eight. This is RbCl's highest possible coordination number. Therefore, according to the radius ratio rule, cations in this polymorph will reach their largest apparent radius because the anion-cation distances are greatest.[4]
Sphalerite (tetrahedral 4:4)
The sphalerite polymorph of rubidium chloride is extremely rare, resulting in few structural studies. The lattice energy, however, for this formation is predicted to nearly 40.0 kJ/mol smaller than those of the preceding structures.[5]
Synthesis
The most common preparation of pure rubidium chloride involves the reaction of its hydroxide with hydrochloric acid, followed by recrystallization:[6]
- RbOH(aq) + HCl(aq) → RbCl(aq) + H2O(l)
Because RbCl is hygroscopic, it must be protected from atmospheric moisture, e.g. using a desiccator. RbCl is primarily used in laboratories. Therefore, numerous suppliers (see below) produce it in smaller quantities as needed. It is offered in a variety of forms for chemical and biomedical research.
Reactions
Rubidium chloride reacts with sulfuric acid to rubidium hydrogen sulfate.
Uses
- Rubidium chloride has been shown to modify coupling between circadian oscillators via reduced photaic input to the suprachiasmatic nuclei. The outcome is a more equalized circadian rhythm, even for stressed organisms.[7]
- RbCl is an excellent non-invasive biomarker. The compound dissolves well in water and readily be taken up by organisms. Once broken in the body, Rb+ replaces K+ in tissues because they are from the same chemical group.[8] An example of this is the use of a radioactive isotope to evaluate perfusion of heart muscle.
- RbCl transformation for competent cells is arguably the compound's most abundant use. Cells treated with a hypotonic solution containing RbCl expand. As a result, the expulsion of membrane proteins allows negatively charged DNA to bind.[9]
- RbCl has been used as an antidepressant in Europe under the trade name Rubinorm in doses ranging from 180 to 720 mg.[10][11][12] Every 18 mg of RbCl is approximately equivalent to 1 Banana equivalent dose due to the large fraction (27.8%) of naturally occurring isotope Rubidium-87. It increases dopamine and norepinephrine levels and has stimulating effects, hence it is useful for anergic and apathetic depressives.[10]
References
- ↑ Lide, D. R.; Cahill, P.; Gold, L. P. (1963). "Microwave Spectrum of Lithium Chloride". Journal of Chemical Physics 40 (1): 156–159. doi:10.1063/1.1724853.
- ↑ 2.0 2.1 Wells, A. F. (1984). Structural Inorganic Chemistry. Oxford University Press. pp. 410, 444.
- ↑ Kopecky, M.; Fábry, J.; Kub, J.; Busetto, E.; Lausi, A. (2005). "X-ray diffuse scattering holography of a centrosymmetric sample". Applied Physics Letters 87 (23): 231914.
- ↑ 4.0 4.1 Shriver, D. F.; Atkins, P. W.; Cooper, H. L. (1990). "Chapter 2". Inorganic Chemistry. Freeman.
- ↑ 5.0 5.1 Pyper, N. C.; Kirkland, A. I.; Harding, J. H. (2006). "Cohesion and polymorphism in solid rubidium chloride". Journal of Physics: Condensed Matter 18 (2): 683–702. doi:10.1088/0953-8984/18/2/023.
- ↑ Winter, M. (2006). "Compounds of Rubidium". WebElements.
- ↑ Hallonquist, J.; Lindegger, M.; Mrosovsky, N. (1994). "Rubidium chloride fuses split circadian activity rhythms in hamsters housed in bright constant light". Chronobiology International 11 (2): 65–71. doi:10.3109/07420529409055892. PMID 8033243.
- ↑ Hougardy, E.; Pernet, P.; Warnau, M.; Delisle, J.; Grégoire, J.-C. (2003). "Marking bark beetle parasitoids within the host plant with rubidium for dispersal studies". Entomologia Experimentalis et Applicata 108 (2): 107. doi:10.1046/j.1570-7458.2003.00073.x.
- ↑ "RbCl Transformation Protocol". New England Biolabs. 2006.
- ↑ 10.0 10.1 Baumel, S. (2000). Dealing with depression naturally: complementary and alternative therapies for restoring emotional health. Los Angeles: Keats Pub. p. 101. ISBN 0-658-00291-0.
- ↑ Budavari, S. (1996). The Merck index: an encyclopedia of chemicals, drugs, and biologicals. Rahway, NJ, U.S.A.: Merck. ISBN 0-911910-12-3.
- ↑ Lake, J. A. (2006). Textbook of Integrative Mental Health Care. New York: Thieme Medical Publishers. p. 165. ISBN 1-58890-299-4.
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