Bromoethane

Chembox new
Name = Bromoethane
ImageFile = Bromoethane.png ImageName = Bromoethane
ImageFile1 = Bromoethane-3D-vdW.png ImageName1 = Bromoethane
OtherNames = Ethyl bromide
Section1 = Chembox Identifiers
SMILES = CCBr
CASNo = 74-96-4
RTECS = KH6475000
Section2 = Chembox Properties
Formula = C₂H₅Br
MolarMass = 108.97 g/mol
Appearance = Colourless liquid
Density = 1.47 g/cm³, liquid
Solubility = 0.91 g/100 ml (20 °C)
MeltingPt = −119 °C (154 K)
BoilingPt = 38.4 °C
Viscosity = 0.402 cP at 20 °C
Section3 = Chembox Structure
Dipole =
Section7 = Chembox Hazards
ExternalMSDS =
EUClass = Flammable (F)
Carc. Cat. 3
Harmful (Xn)
NFPA-H = 2
NFPA-F = 1
NFPA-R =
RPhrases = R11, R20/22, R40
SPhrases = S2, S36/37
FlashPt = −20 °C
Autoignition = 511 °C
ExploLimits = 6.8–11%
Section8 = Chembox Related
Function = haloalkanes
OtherFunctn = bromomethane
Chloroethane
Iodoethane

Bromoethane, also known as ethyl bromide is a chemical compound of the haloalkanes group. It is abbreviated by chemists as EtBr. This volatile compound has an ether-like odour.

ynthesis

The preparation of EtBr stands as a model for the synthesis of alkyl bromides in general. It is usually prepared by the addition of HBr to ethylene::H₂C=CH₂ + HBr → H₃C-CH₂Br

Ethyl bromide is inexpensive and would rarely be prepared in the laboratory. Convenient laboratory syntheses include the action of phosphorus tribromide or thionyl bromide on ethanol. EtBr forms when ethanol is treated with HBr or hydrobromic acid, although this reaction also affords diethyl ether.

Uses

In organic synthesis, EtBr is the synthetic equivalent of the ethyl carbocation (Et⁺) synthon. In reality, such a cation is not actually formed. For example, carboxylates salts are converted to ethyl esters, [OrgSynth | author = Petit, Y.; Larchevêque, M. | title = Ethyl Glycidate from (S)-Serine: Ethyl (R)-(+)-2,3-Epoxypropanoate | volume = 75 | pages = 37 | collvol = 10 | collvolpages = 401 | prep = v75p0037] carbanions to ethylated derivatives, thiourea into ethylisothiouronium salts, [OrgSynth | author = E. Brand, E.; Brand, F. C. | title = Guanidodacetic Acid | volume = 22 | pages = 59 | collvol = 3 | pages = 440 | prep = cv3p0440] and amines into ethylamines. [OrgSynth | author = Brasen, W. R; Hauser, C. R. | title = o-Methylethylbenzyl Alcohol | volume = 34 | pages = 58 | collvol = 4 | collvolpages = 582 | prep = cv4p0582]

Being a liquid at room temperature but still very volatile, EtBr is an inexpensive reagent for the preparation of Grignard reagents, which traditionally were used as strong base. Thus EtMgBr deprotonates alkynes: [OrgSynth | author = Taniguchi, H.; Mathai, I. M.; Miller, S. I. | title = 1-Phenyl-1,4-Pentadiyne and 1-Phenyl-1,3-Pentadiyne | volume = 50 | pages = 97 | collvol = 6 | collvolpages = 925 | prep = cv6p0925] [OrgSynth | author = A. J. Quillinan, A. J.; Scheinmann, F. | title = 3-Alkyl-1-alkynes Synthesis: 3-Ethyle-1-hexyne | volume = 58 | pages = 1 | collvol = 6 | collvolpages = 595 | prep = cv6p0595] [OrgSynth | author = Newman, M. S.; Stalick, W. M. | title = 1-Ethoxy-1-butyne | volume = 57 | pages = 65 | collvol = 6 | collvolpages = 564 | prep = cv6p0564]

:EtBr + Mg → EtMgBr:RC≡CH + EtMgBr → RC≡CMgBr + EtHThis application has been supplanted by the wide availability of organolithium reagents.

afety

Halocarbons in general are potentially dangerous alkylating agents. Bromides are more superior alkylating agents than chlorides, thus exposure to EtBr should be minimized. EtBr is classified by the State of California as carcinogenic and a reproductive toxin.

References

*

External links

* [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc13/icsc1378.htm International Chemical Safety Card 1378]
* [http://www.cdc.gov/niosh/npg/npgd0265.html NIOSH Pocket Guide to Chemical Hazards]
* [http://www-cie.iarc.fr/htdocs/monographs/vol71/068-bromoeth.html IARC Monograph: "Bromoethane"]