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Information about Alkyl

An alkyl is a univalent (or free) radical containing only carbon and hydrogen atoms arranged in a chain. The alkyls form a homologous series with the general formula CnH2n+1. Examples include methyl, CH3· (derived from methane) and butyl C4H9· (derived from butane). They are normally not found on their own but are found as part of larger branched chain organic molecules. On their own they are free radicals and therefore extremely reactive.

The structure of an alkyl is the same as its straight chained alkane counterpart but with one less hydrogen atom. For example, this is the structure of methyl, the smallest alkyl:



Alkyls are radicals since only three out of four valency electrons are used in bonding on one of the carbon atoms.

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 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 where alkyls are formed instantly is chlorination. This reaction involves chlorine free radicals, formed by photodissociation, 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.

Alkyls are very commonly observed in mass spectroscopy of organic compounds.

Naming Alkyls

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

Number of carbons123456789101112
Prefixmeth-eth-prop-but-pent-hex-hept-oct-non-dec-undec-dodec-
Molecule nameMethylEthylPropylButylPentylHexylHeptylOctylNonylDecylUndecylDodecyl

Branched chained structures

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



The structure of 3-methylpentane consist of two parts. Firstly, the longest straight chain of carbon atoms, 5 carbons long with all single bonds, which is named pentane (highlighted blue). Secondly, 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 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.)



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 was 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

In chemistry, valence, also known as valency or valency number, is a measure of the number of chemical bonds formed by the atoms of a given element. Over the last century, the concept of valence evolved into a range of approaches for describing the chemical bond,
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radicals (often referred to as free radicals) are atomic or molecular species with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly reactive, so radicals are likely to take part in chemical reactions.
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4, 2
(mildly acidic oxide)
Electronegativity 2.55 (Pauling scale)
Ionization energies
(more) 1st: 1086.5 kJmol−1
2nd: 2352.6 kJmol−1
3rd: 4620.5 kJmol−1

Atomic radius 70 pm
Atomic radius (calc.
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1, −1
(amphoteric oxide)
Electronegativity 2.20 (Pauling scale) More

Atomic radius 25 pm
Atomic radius (calc.) 53 pm
Covalent radius 37 pm
Van der Waals radius 120 pm
Miscellaneous

Thermal conductivity (300 K) 180.
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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
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Methane is a chemical compound with the molecular formula CH4. It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.
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Butane, also called n-butane, is the unbranched alkane with four carbon atoms, CH3CH2CH2CH3. Butane is also used as a collective term for n
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radicals (often referred to as free radicals) are atomic or molecular species with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly reactive, so radicals are likely to take part in chemical reactions.
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Alkanes, also known as Paraffins, are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i.e. hydrocarbons), where each of these atoms are linked together exclusively by single bonds (i.e. they are saturated compounds) without any cyclic structure (i.
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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 volatile liquid on a cold day,
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radicals (often referred to as free radicals) are atomic or molecular species with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly reactive, so radicals are likely to take part in chemical reactions.
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Mass spectrometry (previously called mass spectroscopy ()[1] or informally, "mass-spec" and MS) is an analytical technique used to measure the mass-to-charge ratio of ions.
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organic compounds]] 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, carbon oxides and cyanides, as well as elemental carbon are
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Alkanes, also known as Paraffins, are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i.e. hydrocarbons), where each of these atoms are linked together exclusively by single bonds (i.e. they are saturated compounds) without any cyclic structure (i.
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The suffix -yl is used in organic chemistry to form names of radicals, either separate or as chemically bonded parts of molecules. It was extracted from the word methyl, whose etymology is described in Methanol#History.
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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 (IUPAC).
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In chemistry, a methyl group is a hydrophobic alkyl functional group derived from methane (CH4). It has the formula -CH3 and is very often abbreviated as -Me in the structure of a molecule. This hydrocarbon unit can be found in many organic compounds.
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Ethyl may refer to:
  • Ethyl group, a functional group in organic chemistry
  • Ethyl Corporation, a fuel additive company

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In organic chemistry, propyl is a three-carbon alkyl substituent with chemical formula -C3H7. It is the substituent form of the alkane propane.

For example:

This is propyl ethanoate, an ester.
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In organic chemistry, butyl is a four-carbon alkyl substituent with chemical formula -C4H9 . It is derived from either of the two isomers of the alkane called butane.
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pentyl is a five-carbon alkyl substituent with chemical formula -C5H11. It is the substituent form of the alkane pentane.

Examples

  • Pentanol
  • Pentyl pentanoate
  • Amylamine
  • Amyl acetate
  • Amyl alcohol

Nomenclature


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4, 2
(mildly acidic oxide)
Electronegativity 2.55 (Pauling scale)
Ionization energies
(more) 1st: 1086.5 kJmol−1
2nd: 2352.6 kJmol−1
3rd: 4620.5 kJmol−1

Atomic radius 70 pm
Atomic radius (calc.
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Alkanes, also known as Paraffins, are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i.e. hydrocarbons), where each of these atoms are linked together exclusively by single bonds (i.e. they are saturated compounds) without any cyclic structure (i.
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aryl refers to any functional group or substituent derived from a simple aromatic ring. There are more specific terms, such as phenyl, to describe unsubstituted aryl groups and subsets of aryl groups (as well as arbitrarily substituted groups: see IUPAC nomenclature), but "aryl" is
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The IUPAC nomenclature of organic chemistry is a systematic method of naming organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC).
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