Strontium bromide

Strontium bromide is a chemical compound with a formula SrBr₂. At room temperature it is a white, odourless, crystalline powder. Strontium bromide imparts a bright red colour in a flame test, showing the presence of strontium ions. It is used in flares and also has some pharmaceutical uses.

Strontium bromide

Names
IUPAC name Strontium bromide
Identifiers
CAS Number	10476-81-0 Y
3D model (JSmol)	Interactive image
ChemSpider	23635 Y
ECHA InfoCard	100.030.868
EC Number	233-969-5
PubChem CID	25302
UNII	1NG558X5VJ Y
CompTox Dashboard (EPA)	DTXSID40222486
InChI InChI=1S/2BrH.Sr/h2*1H;/q;;+2/p-2 Y Key: YJPVTCSBVRMESK-UHFFFAOYSA-L Y InChI=1S/2BrH.Sr/h2*1H;/q;;+2/p-2 Key: YJPVTCSBVRMESK-NUQVWONBAI Key: YJPVTCSBVRMESK-UHFFFAOYSA-L
SMILES [Sr+2].[Br-].[Br-]
Properties
Chemical formula	SrBr2
Molar mass	247.428 g/mol (anhydrous) 355.53 g/mol (hexahydrate)
Appearance	white crystalline powder
Density	4.216 g/cm3 (anhydrous) 2.386 g/cm3 (hexahydrate)
Melting point	643 °C (1,189 °F; 916 K)
Boiling point	2,146 °C (3,895 °F; 2,419 K)
Solubility in water	107 g/100 mL
Solubility	Soluble in ethanol Insoluble in diethyl ether
Magnetic susceptibility (χ)	−86.6·10−6 cm3/mol
Structure[1]
Crystal structure	Tetragonal
Space group	P4/n (No. 85)
Lattice constant	a = 1160.42 pm, c = 713.06 pm
Formula units (Z)	10
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Corrosive
NFPA 704 (fire diamond)	1 0 1
Related compounds
Other anions	Strontium fluoride Strontium chloride Strontium iodide
Other cations	Beryllium bromide Magnesium bromide Calcium bromide Barium bromide Radium bromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Preparation

SrBr₂ can be prepared from strontium hydroxide and hydrobromic acid.

Sr(OH)₂ + 2 HBr → SrBr₂ + 2 H₂O

Alternatively strontium carbonate can also be used as strontium source.

SrCO₃ + 2 HBr → SrBr₂ + H₂O + CO₂(g)

These reactions give hexahydrate of strontium bromide (SrBr₂·6H₂O), which decomposes to dihydrate (SrBr₂·2H₂O) at 89 °C. At 180 °C anhydrous SrBr₂ is obtained.^[2]

Structure

At room temperature, strontium bromide adopts a crystal structure with a tetragonal unit cell and space group P4/n. This structure is referred to as α-SrBr₂ and is isostructural with EuBr₂ and USe₂. The compound's structure was initially erroneously interpreted as being of the PbCl₂ type,^[3] but this was later corrected.^[4][1]

Around 920 K (650 °C), α-SrBr₂ undergoes a first-order solid-solid phase transition to a much less ordered phase, β-SrBr₂, which adopts the cubic fluorite structure. The beta phase of strontium bromide has a much higher ionic conductivity of about 1 S/cm, comparable to that of molten SrBr₂, due to extensive disorder in the bromide sublattice.^[1] Strontium bromide melts at 930 K (657 °C).

• 
  Space-filling model of the packing of Sr²⁺ and Br⁻ ions in α-SrBr₂
• 
  Distorted square antiprismatic coordination geometry of crystallographically independent strontium atom number 1
• 
  Square antiprismatic coordination geometry of strontium number 2
• 
  Flattened tetrahedral coordination geometry of bromine number 1
• 
  Distorted tetrahedral coordination geometry of bromine number 2
• 
  Tetrahedral coordination geometry of bromine number 3
• 
  Tetrahedral coordination geometry of bromine number 4

See also

• Strontium chloride