Carbon tetrabromide
 |
|||
|
|||
| Names | |||
|---|---|---|---|
|
IUPAC name
Tetrabromomethane
|
|||
Other names
|
|||
| Identifiers | |||
|
3D model (JSmol)
|
|||
| Abbreviations | R-10B4 | ||
| 1732799 | |||
| ChEBI | |||
| ChemSpider | |||
| ECHA InfoCard | 100.008.355 | ||
| EC Number | 209-189-6 | ||
| 26450 | |||
| MeSH | carbon+tetrabromide | ||
|
PubChem CID
|
|||
| RTECS number | FG4725000 | ||
| UN number | 2516 | ||
|
|||
|
|||
| Properties | |||
| CBr4 | |||
| Molar mass | 331.63 g·mol−1 | ||
| Appearance | Colorless to yellow-brown crystals | ||
| Odor | sweet odor | ||
| Density | 3.42 g mL−1 | ||
| Melting point | 94.5 °C; 202.0 °F; 367.6 K | ||
| Boiling point | 189.7 °C; 373.4 °F; 462.8 K decomposes | ||
| 0.024 g/100 mL (30 °C) | |||
| Solubility | soluble in ether, chloroform, ethanol | ||
| Vapor pressure | 5.33 kPa (at 96.3 °C) | ||
| -93.73·10−6 cm3/mol | |||
|
Refractive index (nD)
|
1.5942 (100 °C) | ||
| Structure | |||
| Monoclinic | |||
| Tetragonal | |||
| Tetrahedron | |||
| 0 D | |||
| Thermochemistry | |||
| 0.4399 J K−1 g−1 | |||
|
Std molar
entropy (S |
212.5 J/mol K | ||
|
Std enthalpy of
formation (ΔfH |
26.0–32.8 kJ mol−1 | ||
|
Gibbs free energy (ΔfG˚)
|
47.7 kJ/mol | ||
|
Std enthalpy of
combustion (ΔcH |
−426.2–−419.6 kJ mol−1 | ||
| Hazards | |||
| Safety data sheet | inchem.org | ||
| GHS pictograms |
 
|
||
| GHS signal word | DANGER | ||
| H302, H315, H318, H335 | |||
| P261, P280, P305+351+338 | |||
| NFPA 704 | |||
| Flash point | noncombustible | ||
| Lethal dose or concentration (LD, LC): | |||
|
LD50 (median dose)
|
|
||
| US health exposure limits (NIOSH): | |||
|
PEL (Permissible)
|
none | ||
|
REL (Recommended)
|
TWA 0.1 ppm (1.4 mg/m3) ST 0.3 ppm (4 mg/m3) | ||
|
IDLH (Immediate danger)
|
N.D. | ||
| Related compounds | |||
|
Related alkanes
|
|||
|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
|||
 (what is   ?) |
|||
| Infobox references | |||
Tetrabromomethane, CBr4, also known as carbon tetrabromide, is a carbon bromide. Both names are acceptable under IUPAC nomenclature.
Tetrabromomethane has two polymorphs: crystalline II or β below 46.9 °C (320.0 K) and crystalline I or α above 46.9 °C. Monoclinic polymorph has space group C2/c with lattice constants: a = 20.9, b = 12.1, c = 21.2 (.10−1 nm), β = 110.5°.Bond energy of C-Br is 235 kJ.mol−1.
Due to its symmetrically substituted tetrahedral structure, its dipole moment is 0 Debye. Critical temperature is 439 °C (712 K) and critical pressure is 4.26 MPa.
The high temperature α phase is known as a plastic crystal phase. Roughly speaking, the CBr4 are situated on the corners of the cubic unit cell as well as on the centers of its faces in an fcc arrangement. It was thought in the past that the molecules could rotate more or less freely (a 'rotor phase'), so that on a time average they would look like spheres. Recent work has shown, however, that the molecules are restricted to only 6 possible orientations (Frenkel disorder). Moreover, they cannot take these orientations entirely independently from each other because in some cases the bromine atoms of neighboring molecules would point at each other leading to impossibly short distances. This rules out certain orientational combinations when two neighbor molecules are considered. Even for the remaining combinations displacive changes occur that better accommodate neighbor to neighbor distances. The combination of censored Frenkel disorder and displacive disorder implies a considerable amount of disorder inside the crystal which leads to highly structured sheets of diffuse scattered intensity in X-ray diffraction. In fact, it is the structure in the diffuse intensity that provides the information about the details of the structure.
...
Wikipedia