JEE Main & Advanced Chemistry Organic Chemistry: Some Basic Principles & Techniques Nomenclature Of Special Compounds

Nomenclature Of Special Compounds

Category : JEE Main & Advanced

Unbranched assemblies consisting of two or more identical hydrocarbon units joined by a single bond are named by placing a suitable numerical prefix such as bi for two, ter for three, quater for four, quinque for five etc. before the name of the repititive hydrocarbon unit. Starting from either end, the carbon atoms of each repititive hydrocarbon unit are numbered with unprimed and primed arabic numerals such as 1, 2, 3...., 1', 2', 3' ....., 1'', 2'', 3''..... etc. The points of attachment of the repititive hydrocarbon units are indicated by placing the appropriate locants before the name. For example,           

As an exception, unbranched assemblies consisting of benzene rings are named by using appropriate prefix with the name phenyl instead of benzene. For example,


  • If two atoms/groups of same preference occupy identical positions from either end of the parent chain, the lower number must be given to the atom/group whose prefix comes first in the alphabetical order. For example,

\[\underset{\text{1-Bromo-4-chlorobutane}}{\mathop{Cl\overset{4}{\mathop{C}}\,{{H}_{2}}\overset{3}{\mathop{C}}\,{{H}_{2}}\overset{2}{\mathop{C}}\,{{H}_{2}}\overset{1}{\mathop{C}}\,{{H}_{2}}Br}}\,\]\[\underset{\text{2 ethoxy-4-methoxy pentan-3-one}}{\mathop{\underset{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,OC{{H}_{3}}}{\mathop{\underset{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|}{\mathop{\overset{5}{\mathop{C}}\,{{H}_{3}}-\overset{4}{\mathop{C}}\,H}}\,}}\,\underset{O}{\mathop{\underset{||}{\mathop{-\overset{3}{\mathop{C}}\,-}}\,}}\,\underset{OC{{H}_{2}}C{{H}_{3}}}{\mathop{\underset{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{\overset{2}{\mathop{C}}\,H-\overset{1}{\mathop{C}}\,{{H}_{3}}}}\,}}\,}}\,\]                

  • When two or more prefixes consist of identical words, the priority for citation is given to that group which contains the lowest locant at the first point of difference. For example,


  • If a compound contains a benzene ring coupled to an alicyclic ring, it is named as a derivative of benzene, i.e. compound having lowest state of hydrogenation. For example,


  • In the common system of nomenclature, prefixes iso and neo are used only for compounds containing an isopropyl group, \[{{(C{{H}_{3}})}_{2}}CH\] and a tert-butyl group, \[{{(C{{H}_{3}})}_{3}}C\] respectively at the end of the carbon chain.

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