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What is Alkylation?

Posted: Mon Nov 13, 2017 10:56 pm
by bejoy
Alkylation:

Alkylation is the process of transferring an alkyl group from one molecule to another. Alkyl substituent is an alkane which have one missing hydrogen atom. It is basically the process of introducing hydrocarbons into chemicals. An alkyl group molecule has general formula as CnH2n+1, where ‘n’ signifies number of carbons associated together. An alkyl group can be transferred as an alkyl free radical, carbonation, a carbanion or as a Carbene.

Alkyl groups can also be removed from the compound by the process Dealkylation.

Alkylating Agents Classification:

1.Nucleophilic Alkylating agents:

These agents deliver anion (negatively charged) alkyl to the hydrocarbon in a compound. These agents can displace halide also. They can also alkylate alkyl and aryl halides, in the presence of catalysts. These agents are used to produce fluoride, chloride, bromide, iodide and astatide elements.

2.Electrophilic Alkylating agents:

These agents deliver cation (positively charged) alkyl to the hydrocarbons in a compound. These groups of alkyl are very toxic in nature. These agents are used in anticancer drugs as they have the ability to alkylate DNA bases.

3.Carbene Alkylating agents:

Carbene Alkylating agents are highly reactive and are also famous for attacking C-H bonds which are not even activated. By elimination of a diazo group, carbenes can be generated. Carbenes agents are neutral and instead of leaving groups they insert into bonds.

Role of Alkylation:

In biology: Alkylation plays a major role in genetics. Methylation is one common type of alkylation where there is transfer of only one carbon methyl. In Methylation one hydrogen atom is replaced by one carbon atom and this reaction in cells is generally mediated by enzymes and it targets DNA. Different nucleophiles in the body can be alkylated by electrophilic agents. Different Methylation relations keep taking place in the human body, which are responsible for different genes expressions or activities of enzymes. Methylation can be reversed by the process demethylation.

In oil refining: In alkylation of petroleum, gaseous hydrocarbons or isopraffins are combined with olefins or alkenes. This process is called as Alkylation unit. Isobutene and alkenes with low molecular weight are converted into a high octane gasoline compound, alkylate. An acid catalyst such as sulfuric acid or hydrofluoric acid is also used. Oil refinery process of alkylation which involves sulfuric acid is called as sulfuric acid alkylation unit (SAAU) and with hydrofluoric acid is called as hydrofluoric alkylation unit (HFAU).

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