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Basic IUPAC Organic Nomenclature

Disubstituted benzenes

Numerical locants method:

  • Principle functional group is the benzne therefore root = benzene
  • There are two chlorine substituents therefore dichloro
  • The substituent lowest locants = 1 and 2
1,2-dichlorobenzene
disubs aromatic
  • Principle functional group is the benzne therefore root = benzene
  • There is a chlorine substituent therefore chloro
  • There is a bromine substituent therefore bromo
  • Numbering from the -Br (due to alphabet priority) clockwise to give the chlorine substituent the lowest locant = 3
1-bromo-3-chlorobenzene
disubs aromatic
  • Principle functional group is the aromatic alcohol therefore = phenol
  • The substituent is a chlorine therefore = chloro
  • Numbering from the -OH, counterclockwise to give the substituent the lowest locant = 2
2-chlorophenol
disusbs aromatic

 

Ortho / meta / para method:

  • Principle functional group is the benzne therefore root = benzene
  • There are two chlorine substituents therefore dichloro
  • The substituent locants are 1 and 2 therefore ortho
ortho-dichlorobenzene
or
o-dichlorobenzene
disubs aromatic
  • Principle functional group is the benzne therefore root = benzene
  • There is a chlorine substituent therefore chloro
  • There is a bromine substituent therefore bromo
  • The substituent locants are 1 and 3 therefore meta
meta-bromochlorobenzene
or
m-bromochlorobenzene
disubs aromatic
  • Principle functional group is the aromatic alcohol therefore = phenol
  • The substituent is a chlorine therefore = chloro
  • The substituent locants are 1 and 2 therefore ortho
ortho-chlorophenol
or
o-chlorophenol
disusbs aromatic


organic chemistry ©Dr. Ian Hunt, Department of Chemistry University of Calgary