Nitration of Benzene
Resonance structure of nitro group
Nitro compounds are obtained by replacing the H–atom of an hydrocarbon with the –NO2 functional group.
The compounds containing more than one nitro group are often highly explosive and are impure. Nitro compounds may be liquids or solids. They are not usually found in nature. They are prepared commercially by nitration of organic compounds.
Eg: Nitration of Benzene.
Nitro Alkanes.
Occurrence:
Nitro compounds are present in the following forms in the nature:
3–Nitropropionic acid found in fungi and plants(Indigofera). Nitropentadecene is a defense compound found in termites.
Chloramphenicol is a rare example of a naturally occurring nitro compound.
2–Nitrophenol is an aggregation pheromone of ticks.
Aromatic nitro compounds
Nitro compounds are characterized by the presence of nitro group(–NO2) in their molecules. They may be aliphatic or aromatic compounds based on whether the nitro group is attached to alkyl or aryl groups.
i.e., R–NO2 (Aliphatic nitro compounds)
Ar–NO2(Aromatic nitro compounds)
The aliphatic nitro compounds may be further classified into primary, secondary or tertiary nitro compounds based on whether the nitro group is attached to primary, secondary or tertiary carbon atom respectively.
Aromatic nitro compounds are called nitroarenes. The position of nitro group and other substituents if any are indicated by Arabic numerals.
The nitro group is an ambidentate group and is capable of getting attached to carbon chain through nitrogen as well as through oxygen (–O–N = O) atom.
The compounds in which the –NO2 group are linked to the alkyl or aryl group through oxygen atom are called nitrites. Nitrites are isomeric with nitro compounds.