Branched-chain alkanes alkyl groups, 752 naming

Alkyl groups You have seen that both a straight-chain and a branched-chain alkane can have the same molecular formula. This fact illustrates a basic principle of organic chemistry the order and arrangement of atoms in an organic molecule determine its identity. Therefore, the name of an organic compound must also accurately describe the molecular structure of the compound. 

Plan Because the hydrocarbon is an alkane, its name ends in -ane. The name of the parent hydrocarbon is based on the longest continuous chain of carbon atoms. Branches are alkyl groups, named after the number of C atoms in the branch and located by counting C atoms along the longest continuous chain. 

Methylethyl is the systematic name for this group isopropyl is a common name. Systematic nomenclature for alkyl groups is similar to that for branched-chain alkanes, with the provision that numbering always begins at the point where the group is attached to the main chain. There are four C4 groups. 

A How To Name Unbranched Alkyl Groups 147 4.3B How To Name Branched-Chain Alkanes 147 4.3C How To Name Branched Alkyl Groups 149 4.3D How To Classify Hydrogen Atoms 151 4.3E How To Name Alkyl Halides 151 4.3F How To Name Alcohols 152... 

Branched alkanes are named as a straight-chain alkane with attached alkyl groups. For example, a single carbon branch wonld be called methyl . They are prefixed with a nnmber indicating the number of the carbon the gronp is attached to, counting from the end of the alkane chain. An example would be a substance that contains five carbons, one of which is a methyl branch on the second carbon this would be called 2-methylbutane. The alternative name 3-methylbutane is incorrect because this scheme requires the lowest numbers to be used. 

Select the longest continuous chain of carbon atoms as the parent compound, and consider all alkyl groups attached to it as branch chains or substituents that have replaced hydrogen atoms of the parent hydrocarbon. If two chains of equal length are found, use the chain that has the larger number of substituents attached to it as the parent compound. The alkane s name consists of the parent compound s name prefixed by the names of the alkyl groups attached to it. 

In Summary Four rules should be applied in sequence when naming a branched alkane (1) Find the longest chain (2) And the names of aU the alkyl groups attached to the ston (3) number the chain (4) name the alkane, with substituent names in alphabetical order and preceded by numbers to indicate their locations. Haloalkanes are named in accord with the rules that apply to naming the alkanes, the halo substituent being treated the same as alkyl groups. 

Alkyl groups are named by an lUPAC procedure similar to that used to name alkanes with the longest continuous chain beginning at the branch point. For example, the lUPAC name for an isopropyl group is 1-methylethyl, and the lUPAC name for an o-butyl group is 2-methylpropyl. The point of attachment of the alkyl group is numbered carbon 1. 

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