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Questions and Answers
What is the result of the reaction between NH3 and HNO2 at 100°C?
Which of the following is a method used for the reduction of nitro groups?
In the mechanism of the nitro group reaction, which species acts slowly in the process?
What compound is formed when NaHS reacts with NaNO2?
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Which of the following best describes the byproducts of the reaction involving CH3ONa?
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What is the major product of the nitration of anisole?
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Which reagent is used alongside concentrated sulfuric acid in the nitration of benzene derivatives?
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Which mechanism facilitates the nitration in the case of anisole?
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What product results from the nitration of phenol?
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What type of substituted benzene is likely to produce a pure o-isomer upon nitration?
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Study Notes
Reaction of Nitro Group
- Nitro group can be reduced by catalytic or chemical reduction methods.
Catalytic Reduction
- Nitro group can be reduced to an amino group by using hydrogen gas and a catalyst like nickel, platinum, or palladium.
Chemical Reduction
- The reduction product of a nitro group depends on the strength of the reducing agent and the pH of the medium.
Reduction in Acidic Medium
- In acidic medium, nitro group is reduced to an amino group using a strong reducing agent like iron, tin, or zinc with hydrochloric acid or SnCl2.
Reduction in Neutral Medium
- In neutral medium, nitro group is reduced to N-phenyl hydroxylamine using zinc with ammonium chloride.
Reduction in Alkaline Medium
- In alkaline medium, nitro group can be reduced to different products depending on the reducing agent and the reaction conditions.
- Using NaOH/CH3OH, a nitro group can be reduced to an azoxybenzene.
- Using SnCl2/NaOH, it can be further reduced to an azobenzene.
- Using Zn/HCl, it forms an azobenzene.
- Using Zn/NaOH, a hydrazobenzene can be formed.
- Using SnCl2/HCl, it is reduced to corresponding amine.
Reactions of Aromatic Nitro Compounds
- Aromatic nitro compounds undergo reactions involving the benzene ring or the nitro group.
Reactions of Benzene Ring
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Aromatic nitro compounds undergo electrophilic aromatic substitution (EAS) reactions, but the nitro group deactivates the ring and directs the incoming electrophile to the meta position.
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The nitro group is electron-withdrawing and meta-directing, restricting the ring's reactivity towards electrophilic aromatic substitution such as Friedel-Crafts alkylation or acylation.
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Nitro groups activate the ring toward nucleophilic aromatic substitution reactions. This activation occurs due to the electron-withdrawing and resonance effects of the nitro group, making it an excellent leaving group.
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The nitro group directs incoming nucleophiles to the ortho and para positions.
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Nucleophilic aromatic substitution reactions typically involve a "Meisenheimer intermediate" which is stabilized by the nitro group.
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There are three main categories of nucleophilic aromatic substitution reactions:
- Substitution of hydride at the ortho and para positions to nitro group.
- Substitution of halide at the ortho or para position to nitro group.
- Substitution of nitro group if multiple nitro groups are at ortho or para positions to each other.
Reactions of Nitro Group
- The nitro group can undergo reactions like reduction or participate in the reactions of the benzene ring, such as EAS or SNAr.
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Description
This quiz covers the various methods of reducing a nitro group into different functional groups in organic chemistry. It includes catalytic and chemical reduction techniques as well as the effects of different pH levels on the reduction process. Test your understanding of these important reduction reactions and their conditions.
