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Alkyl

 

 
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Alkyl
 
 
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An alkyl is a univalent radical
Radical (chemistry)

In chemistry, radicals are atoms, molecules or ions with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly chemical reaction, so radicals are likely to take part in chemical reactions....
 consisting of carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
 and hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
 atoms, arranged in a chain. The Alkyls form homologous series
Homologous series

In chemistry, a homologous series is a series of organic compounds with a similar general formula, possessing similar chemical properties due to the presence of the same functional group, and shows a gradation in physical properties as a result of increase in molecular size and mass ....
 with the general formula CnH2n+1. They include methyl, CH3· (named after methane
Methane

Methane is a chemical compound with the molecular formula . It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees....
), ethyl (C2H5·), propyl (C3H7·), butyl (C4H9·), pentyl (C5H11·), and so on.






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An alkyl is a univalent radical
Radical (chemistry)

In chemistry, radicals are atoms, molecules or ions with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly chemical reaction, so radicals are likely to take part in chemical reactions....
 consisting of carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
 and hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
 atoms, arranged in a chain. The Alkyls form homologous series
Homologous series

In chemistry, a homologous series is a series of organic compounds with a similar general formula, possessing similar chemical properties due to the presence of the same functional group, and shows a gradation in physical properties as a result of increase in molecular size and mass ....
 with the general formula CnH2n+1. They include methyl, CH3· (named after methane
Methane

Methane is a chemical compound with the molecular formula . It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees....
), ethyl (C2H5·), propyl (C3H7·), butyl (C4H9·), pentyl (C5H11·), and so on. They are usually constituents of larger molecules, but, when occurring independently, they are known as "free radical
Radical (chemistry)

In chemistry, radicals are atoms, molecules or ions with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly chemical reaction, so radicals are likely to take part in chemical reactions....
s" and are very reactive.

The structure of an alkyl is like that of its alkane
Alkane

Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon and hydrogen , wherein these atoms are linked together exclusively by single bonds without any cyclic structure ....
 counterpart, but with one less hydrogen atom. For example, this is the structure of methyl, the smallest alkyl:

Alkyl
A secondary alkyl group is branched with the central carbon atom linked to two carbon residues. Likewise, in tertiary alkyl groups, there are three carbon-linked substituents. In neopentane
Neopentane

Neopentane, also called dimethylpropane or 2,2-dimethylpropane, is a double-branched-chain alkane with five carbon atoms. Neopentane is an extremely flammable gas at room temperature and pressure which can condense into a highly Volatility liquid on a cold day, in an ice bath, or when compressed to a higher pressure....
, the central carbon atom is quaternary.

Reactions

Unbonded alkyls are free radicals; therefore they are formed only as instantaneous intermediates in reactions usually involving other free radicals. When a free radical is formed, it very quickly reacts with something else to lose the unpaired electron.

An example of a reaction in which alkyls are formed instantly is chlorination. This reaction involves chlorine free radicals, formed by photodissociation
Photodissociation

Photodissociation, photolysis, or photodecomposition is a chemical reaction in which a chemical compound is broken down by photons. Photodissociation is not limited to visible light, but to have enough energy to break up a molecule, the photon is likely to be an electromagnetic wave with the energy of visible light or higher, such...
, reacting with an organic molecule, usually an alkane. The chlorine free radical will bond with a hydrogen from an alkane, forming hydrochloric acid and leaving an alkyl. This alkyl will then bond to a chlorine to form the product, a chloroalkane. The reaction is very energetic and can be explosive if proper precautions are not taken. This is because of the reactivity of free radicals.

In addition, an alcohol
Alcohol

In chemistry, an alcohol is any organic compound in which a hydroxyl Functional group is bound to a carbon atom of an alkyl or substituted alkyl group....
 is formed when a hydroxyl group is bound to the carbon atom of an alkyl.

Alkyls are very commonly observed in mass spectroscopy of organic compound
Organic compound

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered Inorganic compound....
s.

Naming Alkyls

The naming convention for alkyls is much the same as alkanes. The suffix is always -yl
-yl

The Affix -yl is used in organic chemistry to form names of Radical s, either separate or as chemically bonded parts of molecules. It was extracted from the word methyl, whose etymology is described in Methanol#History....
. The prefix depends on how many carbon atoms are in the molecule. This uses the same system as for alkanes as shown in this table (taken from IUPAC nomenclature
IUPAC nomenclature

IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. It is developed and kept up to date under the auspices of the International Union of Pure and Applied Chemistry ....
):

Number of carbons 1 2 3 4 5 6 7 8 9 10 11 12
Prefix meth- eth- prop- but- pent- hex- hept- oct- non- dec- undec- dodec-
Molecule name Methyl Ethyl
Ethyl group

In chemistry, an ethyl group is an alkyl functional group derived from ethane . It has the chemical formula -Carbon2Hydrogen5 and is very often abbreviated -Et....
 Propyl
Propyl

In organic chemistry, propyl is a three-carbon alkyl substituent with chemical formula -Carbon3Hydrogen7. It is the substituent form of the alkane propane....
 Butyl
Butyl

In organic chemistry, butyl is a four-carbon alkyl radical with chemical formula -C4H9 . It is derived from either of the two isomers of the alkane called butane....
 Pentyl
Pentyl

In organic chemistry, pentyl is a five-carbon alkyl radical with chemical formula -C5H11. It is the substituent form of the alkane pentane....
 Hexyl Heptyl Octyl Nonyl Decyl Undecyl Dodecyl


Branched chained structures

These names are used to name branched chained structures, for example 3-methylpentane:

3 Methylpentanehighlighted
The structure of 3-methylpentane consists of two parts. First, the longest straight chain of carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
 atoms, 5 carbons long with all single bonds, which is named pentane (highlighted blue). Second, there is an alkyl group, which is one carbon long, which is methyl (highlighted red). Alkyl groups are included in the name of the molecule before the root, as in methylpentane. This name is, however, ambiguous, as the methyl branch could be on various carbon atoms. Thus, the name is 3-methylpentane
3-Methylpentane

3-Methylpentane is a branching alkane with the molecular formula C6H14. It is a structural isomer of hexane composed of a methyl group bonded to the third carbon atom in a pentane chain....
 to avoid ambiguity: The 3- is because the methyl is attached to the third of the 5-carbon atoms.

If there is more than one of the same alkyl group attached to a chain, then the prefixes are used on the alkyl groups to indicate multiples (i.e., di, tri, tetra, etc.)

2,3,3trimethylpentane
This compound is known as 2,3,3-trimethylpentane. Here, there are three identical alkyl groups attached to carbon atoms 2, 3, and 3. These numbers are included in the name to avoid ambiguity on the position of the groups, and 'tri' indicates that there are three identical methyl groups. If one of the methyl attached to the third carbon atom were an ethyl group, then the name would become 3-ethyl-2,3-dimethylpentane. Note that, when there are different alkyl groups, they are listed in alphabetical order.

See also

  • Alkane
    Alkane

    Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon and hydrogen , wherein these atoms are linked together exclusively by single bonds without any cyclic structure ....
  • Aryl
    Aryl

    In the context of organic molecules, aryl refers to any functional group or substituent derived from a simple aromatic ring, may it be phenyl, thiophene, indole, etc ....
  • IUPAC nomenclature of organic chemistry
    IUPAC nomenclature of organic chemistry

    The IUPAC nomenclature of organic chemistry is a systematic name method of naming Organic compounds as recommended by the International Union of Pure and Applied Chemistry ....