Tetrabromomethane

Structural formula
General
Surname	Tetrabromomethane
other names	Carbon tetrabromide
Molecular formula	CBr 4
Brief description	colorless crystals with a sweet smell
External identifiers / databases
CAS number 558-13-4 EC number 209-189-6 ECHA InfoCard 100.008.355 PubChem 11205 Wikidata Q423556
properties
Molar mass	331.63 g mol −1
Physical state	firmly
density	2.9608 g cm −3 (100 ° C)
Melting point	90.1 ° C
boiling point	189.5 ° C
solubility	practically insoluble in water
Refractive index	1.5942 (100 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 302-315-318-335 P: 261-280-305 + 351 + 338
MAK	Switzerland: 0.1 ml m −3 or 1.4 mg m −3
Toxicological data	1000 mg kg −1 ( LD 50 ,  rat ,  oral )
Thermodynamic properties
ΔH f 0	29.4 kJ / mol
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Tetrabromomethane (also carbon tetrabromide ) is a chemical compound from the group of bromine hydrocarbons . With him all hydrogen atoms of methane are substituted by bromine atoms . Both names are according to the IUPAC - Nomenclature correctly, depending on whether the connection as organic ( carbon tetrabromide ) or inorganic ( carbon tetrabromide ) compound is considered. The compound is the four- substituted representative of the series of bromomethanes with bromomethane , dibromomethane , tribromomethane and tetrabromomethane.

presentation

Tetrabromomethane is produced by the bromination of methane with elemental bromine . The halogen exchange through the reaction of carbon tetrachloride with aluminum bromide at 100 ° C is more economical .

properties

Physical Properties

Tetrabromomethane is a colorless, non-flammable solid with a melting point of 90.1 ° C, which is in the form of monoclinic crystals at room temperature. The boiling point is 189.5 ° C. Tetrabromomethane is as good as not soluble in water and very soluble in non-polar solvents such as chloroform or toluene .

Due to the spherical shape of the CBr ₄ molecule, tetrabromomethane has an extremely high cryoscopic constant . This means that substances dissolved in CBr ₄ cause a very high reduction in the melting point . It is therefore very well suited as a solvent for the Rast method of determining molar mass . The cryoscopic constant is 80 K kg mol ⁻¹ .

Tetrabromomethane is polymorphic, which means that it occurs in two modifications (α-modification and β-modification), which transform into one another at 46.9 ° C.

The binding energy of the C – Br bond is 235 kJ · mol ⁻¹ .

Due to the highly symmetrical tetrahedral structure, the dipole moment is 0  Debye . The critical temperature is 439 ° C (712 K) with a critical pressure of 4.26 MPa. According to another source, the critical temperature is 724.8 K (451.65 ° C), and the critical pressure 96.3 bar, corresponding to 9.63 MPa.

Chemical properties

Tetrabromomethane is significantly less stable than the two lighter tetrahalomethanes, tetrafluoromethane and carbon tetrachloride . It gives off a bromine atom quite easily, which is why it can be used as a mild brominating agent.

use

In combination with triphenylphosphine , CBr _{4 is used} in the so-called Appel reaction to convert alcohols into alkyl bromides.

Carbon tetrabromide can be used for p- doping of gallium arsenide with carbon (GaAs: C) by means of molecular beam epitaxy (MBE) may be used.

Because of its high density in the molten state, tetra- methylene can be used as a heavy liquid to separate minerals .

literature

• Wendan Cheng, Juan Shen, Dongsheng Wu, Xiaodong Li, Youzhao Lan, Feifei Li, Shuping Huang, Hao Zhang, Yajing Gong: Electronic Origin for Enhanced Nonlinear Optical Response of Complexes from Tetraalkylammonium Halide and Carbon Tetrabromide: Electrostatic Potentials of Intermolecular Donor-Acceptor Dyads , in: Chemistry - A European Journal , 2006 , 12  (26), pp. 6880-6887; doi: 10.1002 / chem.200501415 .

Web links

Commons : Tetrabromomethane  - Collection of images, videos and audio files

Individual evidence

1. ↑ ^{a b c d e f g} Entry on tetrabromomethane in the GESTIS substance database of the IFA , accessed on December 29, 2012(JavaScript required) .
2. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-468.
3. ↑ Swiss Accident Insurance Fund (Suva): Limits - Current MAK and BAT values (search for 558-13-4 or carbon tetrabromide ), accessed on May 17, 2020.
4. ↑ Tetrabromomethane data sheet (PDF) from Merck , accessed on January 2, 2013.
5. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-19.
6. ^ ^{A b} N. N. Greenwood, A. Earnshaw: Chemistry of the elements , 1st edition, VCH, Weinheim 1988, ISBN 3-527-26169-9 , p. 359.
7. ↑ M. Brandstätter, L. Kofler: Molecular weight determination under the microscope , in: Microchimica Acta , 1949 , 34 , pp. 364-373. ISSN  0026-3672 (Print) ISSN  1436-5073 (Online)
8. ↑ H. Keller, H. von Halban: About a modification of the micro-cryoscopic molecular weight determination according to Rast , in: Helvetica Chimica Acta , 1944 , 27 , pp. 1439-1443.
9. ^ ^{A b} F. Brezina, J. Mollin, R. Pastorek, Z. Sindelar: Chemicke tabulky inorganicickych sloucenin ( Chemical tables of inorganic compounds ). SNTL, 1986.
10. ↑ A. Pavlovska, D. Nenow: Experimental study of the surface melting of tetrabrommethane , in: Journal of Crystal Growth , 1977 , 39  (2), pp. 346-352; doi: 10.1016 / 0022-0248 (77) 90284-6 .
11. ↑ VDI-Wärmeatlas [Electronic Resource] / VDI Society for Process Engineering and Chemical Engineering (ed.). Springer, 2006.
12. ↑ R. Appel: Tertiary Phosphane / Tetrachloromethane, a Versatile Reagent for Chlorination, Dehydration, and P – N Linkage , in: Angew. Chem. Int. Ed. Engl. , 1975 , 14 (12) , pp. 801-811; doi: 10.1002 / anie.197508011 .
13. ↑ QF Huang: Carbon doping in GaAs using carbon tetrabromide in solid source molecular beam epitaxy , in: Journal of Crystal Growth , 2003 , 252 (1-3) , pp. 37-43; doi: 10.1016 / S0022-0248 (02) 02503-4 .