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 * Bromine **

Bromine (Br) is a chemical element, with atomic number of 35, atomic mass of 79.904. Its electron configuration is 2.8.8.18.7 or 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p5. It is a group VII element, also known as the halogens. It is in Period 4. It needs one more electron to attain the noble-gas configuration of krypton. In its pure form, it forms the diatomic molecule Br2.

Image from: []


 * Reactions in non-organic chemistry**

Bromine usually goes through the following reaction:

Br2 (g) + e- → 2Br-

At the same time, the following displacement reactions involving bromine can occur:

Bromine being displaced:

F2 + 2Br- → 2F- + Br2

Cl2 + 2Br- → 2Cl- + Br2

Bromine displaces iodine:

Br2 + 2I- → 2Br- + I2

Also, bromine undergoes the following photochemical reaction, forming the bromine free radical (The free radical is neutrally charged, but has unpaired electrons):

Br2 ⇌ 2 Br**·**

This free radical bonds readily to other elements.

Reactions with hydrogen:

H2 + Br2 → 2HBr

This reaction occurs slowly on heating.


 * Reactions in organic chemistry**

Organic compounds can be brominated such as bromomethane. This usually happens by electrophilic addition (shown below) or substitution. Image from: []

Hydrolysis of bromomethane (used as an example).

CH3CH2Br + H2O → CH3CH2OH + HBr

Elimination reactions

Bromine can be eliminated, when refluxed with pure NaOH.

CH3CH2Br + NaOH → CH2=CH2 + NaBr + H2O

Bromine compounds

Bromine is a halogen, so besides in brominated organic compounds, it can also form salts. Examples include, NaBr, LiBr, AgBr etc.

Applications of bromine

Bromine compounds can be used as fire retardants as they produce hydrobromic acid which interferes with combustions.

Methyl Bromine was also used as pesticides.

Bromine salts such as potassium bromide are used as sedatives and anticonvulsants (treats seizures).

References: [] and others

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