Aromatic HC-2

​Chapter - 4

AROMATIC COMPOUNDS-2 (Nomenclature)

• ​Monosubstituted benzene derivatives do not exhibit isomerism.

• However, when two substituents are present, there are three possible isomers depending upon the relative positions of the substituents within the ring.

• These relative positions are indicated by the Latin words ortho, meta or para, or their initials: (o-m-p)

​(Isomerism in Benzene Derivatives)

• ​When the substituents are on neighbouring carbon atoms, (1,2–), they are in the ortho– position.

• ​When the position of the substituents on the ring is (1, 3–); they are in the meta– position.

• ​In the third position, the substituents are opposite each other in the position (1,4–). This is the para-position

• ​When the substituents are different; we number the ring beginning with the substituent first in the alphabet, and number in the direction that gives the next substituent the lowest number possible.

• ​As in isomers of other hydrocarbons, the physical and chemical properties of the structural isomers of aromatic hydrocarbons differ.

• The physical properties of the three positional isomers of dimethylbenzene (xylene) are given in Table.

Multiple Choice

Which is the correct drawing of o-bromonitrobenzene?

Multiple Choice

Which is the correct drawing of p-bromonitrobenzene?

Multiple Choice

name this compound

• m-aminochlorobenzene

• m-chloroaniline

• o-chloroaniline

• 1-chloro-3-aminobenzene

Multiple Choice

IUPAC name for this compound is

• 3-methylnitrobenzene

• 3-nitromethylbenzene

• m-toluenenitrobenzene

Multiple Choice

What is the correct name of this compound?

• butanoylbenzene

• 1-phenyl-butan-3-ol

• 1-phenyl-butan-2-ol

• hydroxyethylbenzene

Multiple Choice

what is the name of the following hydrocarbons

• cyclopropane

• cyclopropyl benzene

• propyl benzene

• benzene

Multiple Choice

What is the name of this compound?

• o-pheno

• m-phenol

• o-chlorophenol

• p-chlorophenol

• m-chlorophenol

• ​When three or more of the same substituents are present, numbering starts with the substituent that gives the smallest set of numbers.

• ​When two or more types of substituent are present they are written in alphabetical order.

• When there is a derivative of toluene, aniline or phenol, the substituent responsible for the parent name is assumed to be in position 1 and the other substituents are numbered as usual.

​Example : Name the following compounds

Solution :

​Example: Name the compounds below.

Solution :

Multiple Choice

Name the following

• 2,4,6-Trinitrotoluene

• Trinitro benzene

• 1,3,5-Trinitrotoluene

Multiple Choice

what is the name of the following compound

• 1,4,5-trimethylbenzen

• 1,2,4-trimethylbenzen

• 1-ethyl-2,5-dimethylbenzen

• 3-ethyl-1,4-dimethylbenzen

​Example : Draw the structures of the following aromatic compounds.

a) m-nitrotoluene

b) p-dinitrobenzene

c) 1,3-dichloro-5-nitrobenzene

d) nitrobenzene

e) triphenylmethane