Question
Sun December 11, 2011 By: Nancy Mishra

im not able to understand the steps involved in the IUPAC nomenclature for branched chain saturated hydrocarbons......in addition to this im not getting that how does 2-methylpropane differ from isobutane coz both of them have same structues?Can i write isobutane instead of methyl propane?What difference would it make?

Expert Reply
Mon December 12, 2011
Yes. Both the names are correct but according to IUPAC 2-methylpropane is correct.  
For branched chain nomenclature :
  • Identify each of the branches (side-chains).

     

  • Use the lowest number combinations for the branches (side-chains).

     

  • Name each branch or side-chain (alkyl group) :
    methyl CH3
    ethyl C2H5
    propyl C3H7

     

  • For more than 1 of the same alkyl group use:
    di = 2
    tri = 3
    tetra = 4

     

  • Use commas between numbers, eg, 1,2 or 2,3

     

  • Use hyphens between numbers and words, eg, 2-methyl or 2,3-dimethyl

     

  • If there is more than 1 type of branch or side-chain, arrange their names alphabetically, 
    ie, ethyl groups are named before methyl groups which are named before propyl groups
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