Alkylation

Alkylation is a chemical process through which an alkyl group is attached to some organic substrate molecule by methods like addition and substitution. The Alkyl group is an alkane that lacks one hydrogen atom. A methyl group is the simplest alkyl group consisting of one carbon atom and three hydrogen atoms. Alkylation occurs in the presence of strong mineral acid or lewis acid, such as metal oxides, by using electrophilic alkylating agents like olefin and alkyl halide. In the case of aromatic compounds, alkylation leads to the addition of some simple carbon chains to the benzene ring. There is a contrasting process to alkylation known as dealkylation, which involves the removal of the alkyl group from a compound. There are several types of alkylating agents, and there are several uses of alkylation not just in organic chemistry but also in the field of  biology.

Types of Alkylating Agents 

• Nucleophilic alkylating agents :

Nucleophilic alkylating agents form a species called carbanion. These alkylating agents displace halide substitutes on the given carbon atom via an SN2 mechanism. One of the most common examples of a reaction involving nucleophilic alkylating agents is “Suzuki coupling”, which involves displacement of a halide group from the compound. Examples of nucleophilic alkylating agents are grignard reagents and some more organometallic compounds.

•  Alkylation by electrophilic alkylating agents :

Electrophilic alkylating agents produce carbocation, which is also equivalent to an alkyl cation. This alkylating agent group includes alkyl halides like trimethyloxonium and tetrafluoroborate due to their overt positive charge and inert leaving group. The catalysts used for this alkylation are lewis acid and bronsted acid. Lewis acids like aluminium trichloride. Lewis acids are usually used when alkyl halides are being used. Bronsted acids are used in case alkylation is being done with olefins. Some most common catalysts are zeolites.

There are several hazards of using electrophilic alkylating agents because this type of alkylating agent is toxic and carcinogenic and tends to alkylate the DNA. Consequently, the DNA gets coiling problems because alkylated DNA does not coil or uncoil properly, or it cannot be processed by the specific enzymes used to decode information. The most widely used alkylation reaction is Friedel Crafts Alkylation reaction.

Friedel Crafts Alkylation Reaction 

This reaction involves adding an alkyl group to benzene via an electrophilic aromatic substitution reaction—for example, the addition of a methyl group to benzene. A pi bond attacks a carbocation from an aromatic ring in this reaction. Thus the carbocation acts like an electrophile in Friedel-crafts alkylation. 

Friedel Crafts Alkylation reaction is

Uses of Alkylation in Biology 

One of the most common types of alkylation , methylation, is affected by vitamin B-12 and radical-SAM-based enzymes in nature. Methylation is a chemical reaction involving shifting a methyl group to some organic compound. It can be done via addition reaction or substitution reaction, and there are two types of methylation: chemical methylation and biological methylation. Other biological uses of alkylation are: it is used for the treatment of breast cancer, germ-cell testicular cancer, ovarian cancer and lung cancer, to name a few.

Uses of Alkylation in Daily Use Products 

There are several daily use products like feedstock and detergents. For instance, sodium dodecylbenzene is obtained by the alkylation of benzene with dodecane. 

Uses of Alkylation in Gasoline 

Alkylation plays a significant role in oil refinery operations by alkylating isobutane. Some alkenes have a lesser molecular weight in the presence of bronsted acid and zeolite as a catalyst. Alkylate is also an essential part of avgas.

Conclusion 

Alkylation is a chemical reaction that involves shifting an alkyl group from one molecule to another. The alkyl group that is being shifted is not bound to any particular form and can exist in any form like carbanion, carbocation, free radical, carbene etc. The alkyl group is an alkane having one hydrogen less than its alkane form. Alkylation takes place in the presence of strong lewis acid or bronsted acid. There are different types of alkylating agents like nucleophilic alkylating agents in which the species formed by a nucleophilic alkylating agent would be carbanion or electrophilic alkylating agents, which produces carbocation. The most common Alkylation reaction is Friedel Crafts Alkylation Reaction. There are some hazards of nucleophilic alkylating agents like– they are toxic and carcinogenic and tend to alkylate the DNA. Consequently the DNA gets coiling problems which is because alkylated DNA does not coil or uncoil properly or it cannot be processed by the specific enzymes which are used to decode information. One of the most common alkylation reactions is Friedel-crafts -alkylation; this is an alkylation involving adding an alkyl group to benzene. Alkylation reactions are of high utility. They are used extensively in biology to treat several cancers like breast cancer, lung cancer, etc. It is used in nature too in several biochemical processes. It is also used in daily life and gasoline production as alkylate sposses anti-knock properties.