Organic Chemistry – Some Basic Principles and Techniques

Chemistry · Class 11

Simulation · Chemistry · Class 11

Find the parent chain, then name it

From the lesson IUPAC nomenclature in Organic Chemistry – Some Basic Principles and Techniques. Change the values and watch what happens.

Find the parent chain, then name itChemistry · Class 11

The idea behind it

NCERT § "Nomenclature of Organic Compounds"

  • An IUPAC name is built from a root word (length of the parent chain), a primary suffix (ane, ene, yne), a secondary suffix for the principal functional group and prefixes for substituents.
  • Choose the longest carbon chain as the parent; if two chains are equally long, choose the one with more substituents.
  • Number the chain so that the substituents (or the principal group, or multiple bonds) get the lowest set of locants.
  • Substituent prefixes are written in alphabetical order; multiplying prefixes such as di-, tri- and tetra- are ignored when alphabetising.
  • When several functional groups are present, the principal group takes the suffix; the order of preference is –COOH > –SO₃H > –COOR > –COCl > –CONH₂ > –CN > –CHO > >C=O > –OH > –NH₂ > >C=C< > –C≡C–.
  • Halogens (–F, –Cl, –Br, –I), –NO₂ and –OR are always written as prefixes (fluoro, chloro, bromo, iodo, nitro, alkoxy), never as suffixes.
  • Example: CH₂=CH–CH₂–CHBr–CH₃ is numbered from the end nearer the double bond, giving 4-bromopent-1-ene rather than 2-bromopent-4-ene.
  • Ring compounds take the prefix cyclo-, as in cyclohexane.
  • In disubstituted benzenes, 1,2-, 1,3- and 1,4- positions are also called ortho (o-), meta (m-) and para (p-).