Bromoethane
[CAS# 74-96-4]

Identification

• Classification: Organic raw materials >> Hydrocarbon compounds and their derivatives >> Hydrocarbon halide
• Name: Bromoethane
• Synonyms: Ethyl bromide
• Molecular Formula: C₂H₅Br
• Molecular Weight: 108.97
• CAS Registry Number: 74-96-4
• EC Number: 200-825-8
• SMILES: CCBr

Properties

• Density: 1.46
• Melting point: -119 °C
• Boiling point: 37-40 °C
• Refractive index: 1.4225-1.4245
• Flash point: -23 °C
• Water solubility: 0.91 g/100 mL (20 °C)

Safety Data

• Hazard Symbols: GHS02;GHS07;GHS08 Danger
• Risk Statements: H225-H302-H332-H351
• Safety Statements: P203-P210-P233-P240-P241-P242-P243-P261-P264-P270-P271-P280-P301+P317-P303+P361+P353-P304+P340-P317-P318-P330-P370+P378-P403+P235-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Carcinogenicity	Carc.	2	H351
Flammable liquids	Flam. Liq.	2	H225
Acute toxicity	Acute Tox.	4	H332
Hazardous for the ozone layer	Ozone 99	1	H420

• Transport Information: UN 1891

Discovery and Applications

Bromoethane, also known as ethyl bromide, is a simple alkyl halide with the molecular formula C₂H₅Br. It is a colorless, volatile liquid with a characteristic ether-like odor, and it belongs to the class of haloalkanes in which a bromine atom is covalently bonded to an ethyl group. Bromoethane is a primary alkyl halide, making it highly reactive in nucleophilic substitution and elimination reactions, which underpins its utility in both laboratory and industrial chemical processes.

The discovery of bromoethane is closely associated with the development of early organic halogenation chemistry in the 19th century. Alkyl bromides, including bromoethane, were initially prepared by the reaction of ethanol with hydrobromic acid in the presence of acid catalysts. This method involves the substitution of the hydroxyl group in ethanol with a bromine atom, generating bromoethane along with water as a byproduct. Later improvements included the use of phosphorus tribromide or other brominating agents to increase yield and minimize side reactions, establishing reliable synthetic routes for large-scale production.

Bromoethane is widely used as an intermediate in organic synthesis. Its primary bromide functionality allows it to act as an alkylating agent, introducing the ethyl group into a variety of compounds. In pharmaceutical chemistry, it is used to synthesize ethylated derivatives of heterocycles, amines, and alcohols, which can modify biological activity, solubility, or metabolic stability. Its reactivity is also leveraged in agrochemical synthesis, where it helps construct ethyl-substituted intermediates for herbicides, insecticides, and fungicides.

In polymer chemistry, bromoethane is employed to generate ethyl-functionalized monomers or cross-linking agents. Through nucleophilic substitution with hydroxyl, amino, or thiol groups, it contributes to the formation of linear or branched polymeric structures, enhancing flexibility or introducing reactive sites for further functionalization. This versatility makes it a valuable reagent in producing specialty polymers and resins with tailored properties.

Mechanistically, bromoethane undergoes S_N2 nucleophilic substitution reactions readily due to its primary carbon-bromine bond. Nucleophiles such as hydroxide, cyanide, thiolate, or amine ions can displace the bromide under mild conditions, forming new carbon-heteroatom bonds. Elimination reactions are also possible under strongly basic conditions, yielding ethene as a product. Its simplicity and predictable reactivity make bromoethane a model compound in studying fundamental organic reaction mechanisms, including the effects of solvent, temperature, and nucleophile strength on reaction rates.

Physically, bromoethane is slightly soluble in water but mixes readily with most organic solvents such as ethers, alcohols, and hydrocarbons. It is highly flammable, volatile, and requires proper storage and handling procedures, including containment in well-ventilated areas and away from heat or ignition sources. Environmental and safety considerations are crucial, as alkyl bromides can be toxic and potentially harmful to aquatic life. Appropriate protective equipment, spill containment, and disposal protocols are essential when working with bromoethane.

Overall, bromoethane is an important chemical intermediate with diverse applications in organic synthesis, pharmaceuticals, agrochemicals, and polymer chemistry. Its primary bromide functionality, high reactivity, and straightforward structure make it a fundamental reagent for introducing ethyl groups, constructing new chemical bonds, and exploring mechanistic pathways in both research and industrial contexts.

References

2020. microRNAs Orchestrate Pathophysiology of Breast Cancer Brain Metastasis: Advances in Therapy. Molecular Cancer, 19.
DOI: 10.1186/s12943-020-1140-x

2017. Evaluating the solvation properties of metal-containing ionic liquids using the solvation parameter model. Analytical and Bioanalytical Chemistry, 410(1).
DOI: 10.1007/s00216-017-0802-z

2015. A facile, stereoselective, one-pot synthesis of resveratrol derivatives. Chemistry Central Journal, 9.
DOI: 10.1186/s13065-015-0102-7