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Carbon tetrabromide

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Carbon tetrabromide
Stereo, skeletal formula of tetrabromomethane
Stereo, skeletal formula of tetrabromomethane
Stereo, skeletal formula of tetrabromomethane
Spacefill model of tetrabromomethane
Spacefill model of tetrabromomethane
Names
Preferred IUPAC name
Tetrabromomethane[2]
Other names
  • Carbon(IV) bromide
  • Carbon bromide, neutral (1:4)
  • Carbon tetrabromide
[1]
Identifiers
3D model (JSmol)
Abbreviations R-10B4[citation needed]
1732799
ChEBI
ChemSpider
ECHA InfoCard 100.008.355 Edit this at Wikidata
EC Number
  • 209-189-6
26450
MeSH carbon+tetrabromide
RTECS number
  • FG4725000
UNII
UN number 2516
  • InChI=1S/CBr4/c2-1(3,4)5 checkY
    Key: HJUGFYREWKUQJT-UHFFFAOYSA-N checkY
  • BrC(Br)(Br)Br
Properties
CBr4
Molar mass 331.627 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
1.5942 (100 °C)
Structure
Monoclinic
Tetragonal
Tetrahedron
0 D
Thermochemistry
0.4399 J K−1 g−1
212.5 J/mol K
26.0–32.8 kJ mol−1
47.7 kJ/mol
−426.2–−419.6 kJ mol−1
Hazards
GHS labelling:
GHS05: Corrosive GHS07: Exclamation mark
Danger
H302, H315, H318, H335
P261, P280, P305+P351+P338
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
0
0
Flash point noncombustible[3]
Lethal dose or concentration (LD, LC):
  • 56 mg kg−1 (intravenous, mouse)
  • 100 mg kg−1 (oral, rat)
NIOSH (US health exposure limits):
PEL (Permissible)
 none[3]
REL (Recommended)
 TWA 0.1 ppm (1.4 mg/m3) ST 0.3 ppm (4 mg/m3)[3]
IDLH (Immediate danger)
 N.D.[3]
Safety data sheet (SDS) inchem.org
Related compounds
Other anions
 Carbon tetrafluoride
Carbon tetrachloride
Carbon tetraiodide
Other cations
 Silicon tetrabromide
Germanium tetrabromide
Tin(IV) bromide
Related alkanes
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Carbon tetrabromide, CBr4, also known as tetrabromomethane, is a bromide of carbon. Both names are acceptable under IUPAC nomenclature.

Production

CBr4 can be obtained by the bromination of methane. The byproducts include other brominated methanes (methyl bromide, dibromomethane and bromoform) and hydrogen bromide. This process is analogous to the chlorination of methane:

Br2 + hν → 2 Br·;
Br· + CH4 → ·CH3 + HBr.
·CH3 + Br2 → CH3Br + Br·.
CH3Br + Br· → ·CH2Br + HBr,
·CH2Br + Br2 → CH2Br2 + Br·,
CH2Br2 + Br· → ·CHBr2 + HBr,
·CHBr2 + Br2 → CHBr3 + Br·,
CHBr3 + Br· → ·CBr3 + HBr,
·CBr3 + Br2 → CBr4 + Br·

Halogen exchange of carbon tetrachloride with aluminium bromide gives higher yields with aluminium chloride as the byproduct:[4]

4 AlBr3 + 3 CCl4 → 4 AlCl3 + 3 CBr4

Physical properties

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°.[5] Bond energy of C–Br is 235 kJ.mol−1.[6]

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.[5]

Plastic crystallinity

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[7] 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.

Chemical reactions

In combination with triphenylphosphine, CBr4 is used in the Appel reaction which converts alcohols to alkyl bromides. Similarly, CBr4 is used in combination with triphenylphosphine in the first step of the Corey–Fuchs reaction, which converts aldehydes into terminal alkynes. It is significantly less stable than lighter tetrahalomethanes. It is made via bromination of methane using HBr or Br2. It can be also prepared by more economical reaction of tetrachloromethane with aluminium bromide at 100 °C.[6]

Uses

It is used as a solvent for greases, waxes, and oils, in plastic and rubber industry for blowing and vulcanization, further for polymerization, as a sedative and as an intermediate in manufacturing agrochemicals. Due to its non-flammability it is used as an ingredient in fire-resistant chemicals.[8]

References

  1. ^ "Carbon compounds: carbon tetrabromide". Retrieved 22 February 2013.
  2. ^ "carbon tetrabromide – Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification. Retrieved 18 June 2012.
  3. ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0106". National Institute for Occupational Safety and Health (NIOSH).
  4. ^ N. N. Greenwood, A. Earnshaw: Chemie der Elemente, 1. Auflage, VCH, Weinheim 1988, ISBN 3-527-26169-9, S. 359.
  5. ^ a b F. Brezina, J. Mollin, R. Pastorek, Z. Sindelar. Chemicke tabulky anorganickych sloucenin (Chemical tables of inorganic compounds). SNTL, 1986.
  6. ^ a b N. N. Greenwood, A. Earnshaw. Chemie prvku (Chemistry of the Elements). Informatorium, Prague, 1993.
  7. ^ Coupled orientational and displacive degrees of freedom in the high-temperature plastic phase of the carbon tetrabromide α-CBr4 Jacob C. W. Folmer, Ray L. Withers, T. R. Welberry, and James D. Martin. Physical Review B 77 in press
  8. ^ "Carbon tetrabromide, puriss, 97% | Ottokemi™". www.ottokemi.com. Retrieved 2024-05-12.
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