Chemical Properties of Nitro Compounds and Properties
→ Reduction : Reduction takes place in different steps. The final product, however depends upon the reaction medium and nature of the reducing agent.
Acidic Medium :
Neutral Medium :
Basic Medium :
→ Electrolytic Reduction : In electrolytic reduction nitrobenzene forms paminophenol by rearrangement in the presence of weak acid or base.
Catalytic reduction :
→ Reduction with Metallic Hydride :
→ Selective Reduction : Selective reduction is the reduction of one NO2 group from two group present in compound into NH2.
→ Hydrolysis : Primary nitro alkanes when heated with conc. HCl or 85% H2SO4 then the salt of carboxylic acid and hydroxylamine is formed.
2° nitroalkane when heated with HCl forms ketone and nitrous acid.
3° nitroakane do not hydrolyse.
→ Reaction with HNO2 : Primary nitroalkane having α — H atom reacts with HNO2.
→ 1° nitroalkane reacts with HNO2 and forms nitrolic acid which dissolve in base and form red colour solution
→ Secondary nitroalkane having α — H reacts with HNO2 and form pseudonitrol whose colour is blue and it is insoluble in base.
→ 3° nitroalkane does not react therefore this reaction is used for differentiation among 1°, 2° and 3° nitroalkane.
→ Halogenation : Primary and secondary nitroalkane having α — H reacts with halogen in presence of NaOH.
Ring substitution reaction of nltrobonzene : stable nitrobenzene gives two type of reaction
- Electrophilic Substitution Reactions
- Nucleophilic Substitution Reactions
→ Electrophilic Substitution Reactions : Nitro group in nitrobenzene is m-directive and deactivating group. Which can be represented in the following resonating structures:
→ Due to —I effect and —M effect of NO2 group, electron density decreass at ortho and para position of ring.
→ That’s why nitrobenzene is less reactive for electrophilic reaction.
→ But electron density is high at m-position so electrophile attacks on mcta position.
→ Nucleophilic Substitution reaction : According to resonance structure of nitrobenzene, positive charge comes on o-and p-position hence nucleophile attacks on o-and p-position. Hence nitrobenzene is o-and p-directive.