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Encyclopedia > Alkyl

An alkyl is a univalent 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 term univalent or monovalent describes atoms with one valence electron, i. ... For other uses, see radical. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... 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 (see relative molecular mass). ... The simplest hydrocarbon, methane, is a gas with a chemical formula of CH4. ... Butane, also called n-butane, is the unbranched alkane with four carbon atoms, CH3CH2CH2CH3. ... In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ...

Contents


Structure

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: An alkane in organic chemistry is a saturated hydrocarbon without cycles, that is, an acyclic hydrocarbon in which the molecule has the maximum possible number of hydrogen atoms and so has no double bonds. ...


Image:Alkyl.png Much smaller file, Fireworks makes huge PNGs. ...


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


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. In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ...


An example of a reaction where alkyls are formed instaneously 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.


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): An alkane in organic chemistry is a type of hydrocarbon in which the molecule has the maximum possible number of hydrogen atoms and so has no double bonds (they are saturated). ... The suffix -yl is used in organic chemistry to form names of radicals. ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ...

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

For example, the first three alkyls are called methyl, ethyl and propyl.


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


Image:3-MethylPentaneHighlighted.png Image File history File links 3-MethylPentane with main branch and alkyl group highlighted. ...


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 ambiguation. General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ...


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.)


Image File history File links 2,3,3triMethylPentane with alkyl groups highlighted. ...


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


  Results from FactBites:
 
Alkyl - Wikipedia, the free encyclopedia (531 words)
The structure of an alkyl is the same as its straight chained alkane counterpart but with one less hydrogen atom.
Alkyls are radicals since only three out of four valency electrons are used in bonding on one of the carbon atoms.
Alkyl groups are included in the name of the molecule before the root, as in methylpentane.
  More results at FactBites »

 
 

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