Rubidium azide

Rubidium azide
Names
	IUPAC name rubidium(1+);azide
	Other names Rubidium azide
Identifiers
CAS Number	22756-36-1 ;
3D model (JSmol)	Interactive image;
ChemSpider	81078 ;
PubChem CID	89824;
CompTox Dashboard (EPA)	DTXSID70945439 ;
	InChI InChI=1S/N3.Rb/c1-3-2;/q-1;+1 Key: GEWQYWRSUXOTOL-UHFFFAOYSA-N ;
	SMILES [N-]=[N+]=[N-].[Rb+];
Properties
Chemical formula	RbN3
Molar mass	127.49 g·mol−1
Appearance	Colorless needles
Density	2.79 g/cm3
Melting point	317–321 °C (603–610 °F; 590–594 K)
Boiling point	Decomposes
Solubility in water	107.1 g/100 g (16°C) ; 114.1 g/100 g (17°C)
Solubility	0.182 g/100 g (16°C, ethanol)
Thermochemistry
Std enthalpy of; formation (ΔfH⦵298)	-0.1 kcal·mol−1
Hazards
NFPA 704 (fire diamond)	4 0 3
Related compounds
Other anions	Rubidium nitrate
Other cations	Lithium azide ; Sodium azide ; Potassium azide ; Silver azide ; Ammonium azide
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
	Infobox references

Rubidium azide is an inorganic compound with the formula Rb N₃. It is the rubidium salt of the azide ion (N^–
₃). Like most azides, it is explosive.^[4]

Preparation[]

Rubidium azide can be created by the reaction between rubidium sulfate and barium azide which results in formation of easily separated insoluble barium sulfate:^[3]

{\ce {Rb2SO4 + Ba(N3)2 -> 2RbN3 + BaSO4}}

In at least one study, rubidium azide was produced by the reaction between butyl nitrite, hydrazine monohydrate, and rubidium hydroxide:

{\ce {C4H9ONO + N2H4*H2O + RbOH ->[{\ce {C_2H_5OH}}] RbN3 + C4H9OH + 3H2O}}

This formula is typically used to synthesize potassium azide from caustic potash.^[5]

Uses[]

Rubidium azide has been investigated for possible use in alkali vapor cells, which are components of atomic clocks, atomic magnetometers and . Azides are desirable starting materials because they decompose into rubidium metal and nitrogen gas when exposed to UV light. According to one publication:

Among the different techniques used to fill microfabricated alkali vapor cell [sic], UV decomposition of rubidium azide (RbN₃) into metallic Rb and nitrogen in Al₂O₃ coated cells is a very promising approach for low-cost wafer-level fabrication.^[6]

Structure[]

At room temperature, rubidium azide has the same structure as potassium hydrogen fluoride; a distorted cesium chloride structure. At 315 °C and 1 atm, rubidium azide will transition to the normal cesium chloride structure. The II/I transition temperature of rubidium azide is within 2 °C of its melting point.^[4]

Rubidium azide has a high pressure structure transition, which occurs at about 4.8 kilobars of pressure at 0 °C. The transition boundary of the II/III transition can be defined by the relationship $P=4.82+0.0240t$ , where $P$ is the pressure in kilobars and $t$ is the temperature in degrees Celsius.^[4]

Reactions[]

As with all azides, it will decompose and release nitrogen gas when heated or severely shocked:

{\ce {2RbN3 ->[\Delta]2Rb + 3N2}}

Hazards[]

At 4.1 kilobars of pressure and about 460 °C, rubidium azide will explosively decompose.^[4] Under normal circumstances, it explodes at 395 °C.^[2] It also decomposes upon exposure to ultraviolet light.^[6]

Rubidium azide is very sensitive to mechanical shock, with an impact sensitivity comparable to that of TNT.^[7]

Like all azides, rubidium azide is toxic.

References[]

^ ^a ^b Perry, Dale (1995-05-17). Handbook of Inorganic Compounds. Online. p. 333. ISBN 9780849386718. Retrieved 31 January 2018.
^ ^a ^b ^c ^d Hart, William; Beumel, O. F.; Whaley, Thomas (22 October 2013). The Chemistry of Lithium, Sodium, Potassium, Rubidium, Cesium and Francium: Pergamon Texts in Inorganic Chemistry. Online: Pergamon Press. p. 438. ISBN 9781483187570. Retrieved 31 January 2018.
^ ^a ^b ^c Hála, Jiri. "IUPAC-NIST Solubility Data Series. 79. Alkali and Alkaline Earth Metal Pseudohalides" (PDF). nist.gov. Retrieved 31 January 2018.
^ ^a ^b ^c ^d ^e Pistorius, Carl W. F. T. (27 December 1968). "Phase Diagrams to High Pressures of the Univalent Azides Belonging to the Space Group D 4hI8-14/mcm" (PDF). Online. pp. 1, 4–5. Retrieved 1 February 2018.
^ Ogden, J. Steven; Dyke, John M.; Levason, William; Ferrante, Francesco; Gagliardi, Laura (2006). "The Characterisation of Molecular Alkali-Metal Azides" (PDF). Chemistry - A European Journal. 12 (13): 3580–3586. doi:10.1002/CHEM.200501101. PMID 16491492. S2CID 16007959. Archived from the original (PDF) on 3 February 2018. Retrieved 2 February 2018.
^ ^a ^b Karlen, Sylvain; Gobet, Jean; Overstolz, Thomas; Haesler, Jacques; Lecomte, Steve (26 January 2017). "Lifetime assessment of RbN₃-filled MEMS atomic vapor cells with Al₂O₃ coating" (PDF). Optics Express. 25 (3): 2187–2194. Bibcode:2017OExpr..25.2187K. doi:10.1364/OE.25.002187. PMID 29519066. Retrieved 17 March 2018.
^ Babu, K. Ramesh; Vaitheeswaran, G. (2013). "Structure, elastic and dynamical properties of KN3 and RbN3: A van der Waals density functional study". Solid State Sciences. Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad. 23: 17–25. arXiv:1311.0979. Bibcode:2013SSSci..23...17R. CiteSeerX 10.1.1.768.1309. doi:10.1016/j.solidstatesciences.2013.05.017. S2CID 94217260.

[handbook-1] Perry, Dale (1995-05-17). Handbook of Inorganic Compounds. Online. p. 333. ISBN 9780849386718. Retrieved 31 January 2018.

[alkali-2] Hart, William; Beumel, O. F.; Whaley, Thomas (22 October 2013). The Chemistry of Lithium, Sodium, Potassium, Rubidium, Cesium and Francium: Pergamon Texts in Inorganic Chemistry. Online: Pergamon Press. p. 438. ISBN 9781483187570. Retrieved 31 January 2018.

[[1]-3] Hála, Jiri. "IUPAC-NIST Solubility Data Series. 79. Alkali and Alkaline Earth Metal Pseudohalides" (PDF). nist.gov. Retrieved 31 January 2018.

[pressure-4] Pistorius, Carl W. F. T. (27 December 1968). "Phase Diagrams to High Pressures of the Univalent Azides Belonging to the Space Group D 4hI8-14/mcm" (PDF). Online. pp. 1, 4–5. Retrieved 1 February 2018.

[hydrazine-5] Ogden, J. Steven; Dyke, John M.; Levason, William; Ferrante, Francesco; Gagliardi, Laura (2006). "The Characterisation of Molecular Alkali-Metal Azides" (PDF). Chemistry - A European Journal. 12 (13): 3580–3586. doi:10.1002/CHEM.200501101. PMID 16491492. S2CID 16007959. Archived from the original (PDF) on 3 February 2018. Retrieved 2 February 2018.

[vaporcell-6] Karlen, Sylvain; Gobet, Jean; Overstolz, Thomas; Haesler, Jacques; Lecomte, Steve (26 January 2017). "Lifetime assessment of RbN₃-filled MEMS atomic vapor cells with Al₂O₃ coating" (PDF). Optics Express. 25 (3): 2187–2194. Bibcode:2017OExpr..25.2187K. doi:10.1364/OE.25.002187. PMID 29519066. Retrieved 17 March 2018.

[elastic-7] Babu, K. Ramesh; Vaitheeswaran, G. (2013). "Structure, elastic and dynamical properties of KN3 and RbN3: A van der Waals density functional study". Solid State Sciences. Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad. 23: 17–25. arXiv:1311.0979. Bibcode:2013SSSci..23...17R. CiteSeerX 10.1.1.768.1309. doi:10.1016/j.solidstatesciences.2013.05.017. S2CID 94217260.

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