IUPAC NOMENCLATURE Naming Of Branched Chain Alkanes-02 Er. Vishwa Vivek Sharma (Chemical Engineer)
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the name of the substituent is prefixed to the name of the parent hydrocarbon and its position on the main chain is indicated by writing the locant before thr prefix. A hyphen is inserted between the locant and the substituent name. prefix. A hyphen(-) is inserted between the locant and the substituent name. CH CH CH3-CH-CH2-CH2-CH or 4 2-Methylpentane, VI
O Alphabetical order of side chains:- In case two or more alkyl group (side chains) are attached to the parent chain, these are prefixed in alphabetical order. Wrong numbering CH-CH-CH-CH,-CH or CH, CH 3-Ethyl-2-methylpentane and not as 2-Methyl-3-ethylpentane
if a substituent is present two or more times, this is indicated by the prefix di-, tri-, tetra-, etc. added to the substituent. The different locants of the substituentare separates by commas. the substituent are separates by commas CH, CH, 3 45 CH,-CH-CH-CHCH or / 2, 3-Dimethylpentane
If the same substituent number are obtain in both directions, the first cited group receives the lowest number. Cl Br 2-Bromo-3-chlorobutane not 3-Bromo-2-chlorobutane 3-Ethyl-5-methylheptane not 5-Ethyl-3-methylheptane CH3 C2H5 2 3 6 7 2 6 5 CH3-CH2 CH-CH2-CH2-CH3 or CH-CHCH-CH-CH CH, r CH3 4-Ethyl-3, 3-dimethylheptane The spelling of the prefixes di-, tri-, and tetra- should not be considered while arranging the substituents alphabetically, as in the above example.
In case the substituent on the parent chain has itselfbranched chain then it is named as a substitutedalkyl group and its carbon chain is numbered from the carbon atomattached to the main chain. The name of this complex substituent is written in a bracket to avoid confusion with the number of main chain 3' CHs 2 CH-CHs 1' CH-CH3 6 8 3 5 5 3 or 1 5-(1', 2-dimethylpropyl)-nonane The multiplicity of substituted substituent,i.e. when the substituent is itself substituted and there are two or more such substituent, these are indicated by numerical prefixes like bis, tris, tetrakis etc
Vishwa Vivek Sharma
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