Chemistry:Beryllium bromide

Beryllium bromide

Names
IUPAC name Beryllium bromide
Identifiers
CAS Number	7787-46-4 Y[ECHA]
3D model (JSmol)	Interactive image
ChemSpider	74208 Y
EC Number	232-115-9
PubChem CID	82230
UNII	T00751H2J8
InChI InChI=1S/Be.2BrH/h;2*1H/q+2;;/p-2 Y Key: PBKYCFJFZMEFRS-UHFFFAOYSA-L Y InChI=1/Be.2BrH/h;2*1H/q+2;;/p-2 Key: PBKYCFJFZMEFRS-NUQVWONBAJ
SMILES Br[Be-2](Br)([Br+]1)[Br+][Be-2]1([Br+]1)[Br+][Be-2]1([Br+]1)[Br+][Be-2]1([Br+]1)[Br+][Be-2]1([Br+]1)[Br+][Be-2]1([Br+]1)[Br+][Be-2]1([Br+]1)[Br+][Be-2]1([Br+]1)[Br+][Be-2]1([Br+]1)[Br+][Be-2]1([Br+]1)[Br+][Be-2]1([Br+]1)[Br+][Be-2]1([Br+]1)[Br+][Be-2]1(Br)Br
Properties
Chemical formula	BeBr2
Molar mass	168.820 g/mol
Appearance	colorless white crystals
Density	3.465 g/cm3 (20 °C)
Melting point	508 °C (946 °F; 781 K)sublimes at 473 °C (883 °F; 746 K)
Boiling point	520 °C (968 °F; 793 K)
Solubility in water	Highly
Solubility	soluble in ethanol, diethyl ether, pyridine insoluble in benzene
Structure
Crystal structure	Orthorhombic
Thermochemistry
Heat capacity (C)	0.4111 J/g K
Std molar entropy (So298)	9.5395 J/K
Std enthalpy of formation (ΔfH⦵298)	−2.094 kJ/g
Hazards
Main hazards	see Berylliosis
GHS pictograms
GHS Signal word	Danger
GHS hazard statements	H350i, H330, H301, H372, H319, H335, H315, H317, H411
GHS precautionary statements	P260, P301+310, P304+340, P305+351+338, P320, P330, P405, P501
NFPA 704 (fire diamond)	0 4 0
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 0.002 mg/m3 C 0.005 mg/m3 (30 minutes), with a maximum peak of 0.025 mg/m3 (as Be)
REL (Recommended)	Ca C 0.0005 mg/m3 (as Be)
IDLH (Immediate danger)	Ca [4 mg/m3 (as Be)]
Related compounds
Other anions	Beryllium fluoride Beryllium chloride Beryllium iodide
Other cations	Magnesium bromide Calcium bromide Strontium 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).
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Infobox references

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Beryllium bromide is the chemical compound with the formula BeBr₂. It is very hygroscopic and dissolves well in water. The Be²⁺ cation, which is relevant to BeBr₂, is characterized by the highest known charge density (Z/r = 6.45), making it one of the hardest cations and a very strong Lewis acid.

Preparation and reactions

It can be prepared by reacting beryllium metal with elemental bromine at temperatures of 500 °C to 700 °C:

Be + Br
2 → BeBr
2

When the oxidation is conducted on an ether suspension, one obtains colorless dietherate:

Be + Br
2 + 2 O(C
2H
5)
2 → BeBr
2(O(C
2H
5)
2)
2

The same dietherate is obtained by suspending beryllium dibromide in diethyl ether:

BeBr
2 2 O(C
2H
5)
2 → BeBr
2(O(C
2H
5)
2)
2

This ether ligand can be displaced by other Lewis bases.is ether ligand can be displaced by other Lewis bases.

Beryllium bromide hydrolyzes slowly in water: BeBr₂ + 2 H₂O → 2 HBr + Be(OH)₂

Structure

Two forms (polymorphs) of BeBr₂ are known. Both structures consist of tetrahedral Be²⁺ centers interconnected by doubly bridging bromide ligands. One form consist of edge-sharing polytetrahedra. The other form resembles zinc iodide with interconnected adamantane-like cages.

Safety

Beryllium compounds are toxic if inhaled or ingested.