Nitrogen Containing Organic Compounds - Preparation of Anilines
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Introduction
- Aniline is a nitrogen-containing organic compound with the chemical formula C6H5N.
- It is also known as aminobenzene, phenylamine, or benzenamine.
- Aniline is an important precursor for a variety of chemical compounds and dyes.
- In this lecture, we will discuss the preparation of anilines.
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Preparation of Anilines
- Reduction of Nitrobenzene
- Nitrobenzene can be reduced to aniline by using reducing agents such as iron and hydrochloric acid (Fe/HCl).
- The reaction can be represented as:
C6H5NO2 + 6H2 → C6H5NH2 + 2H2O.
- Example: Reaction of nitrobenzene with Fe/HCl to form aniline.
- Reduction of Nitrobenzene
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Preparation of Anilines (contd.)
- Reduction of Nitrobenzene (contd.)
- Another method involves the use of tin and hydrochloric acid (Sn/HCl) as reducing agents.
- The reaction can be represented as:
C6H5NO2 + 3Sn + 6HCl → C6H5NH2 + 3SnCl2 + 2H2O.
- Example: Reaction of nitrobenzene with Sn/HCl to form aniline.
- Reduction of Nitrobenzene (contd.)
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Preparation of Anilines (contd.)
- Reduction of Nitrobenzene (contd.)
- Sodium sulfide (Na2S) can also be used as a reducing agent to convert nitrobenzene into aniline.
- The reaction can be represented as:
C6H5NO2 + 6Na2S + 4H2O → C6H5NH2 + 6NaHSO3.
- Example: Reaction of nitrobenzene with Na2S to form aniline.
- Reduction of Nitrobenzene (contd.)
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Preparation of Anilines (contd.)
- Reduction of Nitrobenzene (contd.)
- Reduction can also be achieved using a catalyst such as platinum, palladium, or nickel.
- The reaction takes place in the presence of hydrogen gas (H2).
- Example: Reaction of nitrobenzene with catalytic hydrogenation to form aniline.
- Reduction of Nitrobenzene (contd.)
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Preparation of Anilines (contd.)
- Reduction of Nitrobenzene (contd.)
- Alternatively, reduction of nitro compounds can be carried out using molecular hydrogen (H2) and a metal catalyst such as Raney nickel or palladium on carbon.
- Example: Reaction of nitrobenzene with hydrogen (H2) and Raney nickel catalyst to form aniline.
- Reduction of Nitrobenzene (contd.)
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Preparation of Anilines (contd.)
- Reduction of Nitrobenzene (contd.)
- Reduction using ammonium sulfide (NH4)2S can also be employed to convert nitrobenzene into aniline.
- Example: Reaction of nitrobenzene with (NH4)2S to form aniline.
- Reduction of Nitrobenzene (contd.)
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Preparation of Anilines (contd.)
- Reduction of Nitrobenzene (contd.)
- Aniline can also be prepared by the reduction of aryldiazonium salts with hypophosphorus acid.
- The reaction can be represented as:
C6H5N2+X- + H3PO2 → C6H5NH2 + H3PO3 + X-.
- Example: Reaction of aryldiazonium salt with hypophosphorus acid to form aniline.
- Reduction of Nitrobenzene (contd.)
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Preparation of Anilines (contd.)
- Reduction of Nitrobenzene (contd.)
- Aniline derivatives can also be obtained by the reduction of nitro compounds using various reducing agents.
- Example: Reduction of nitrobenzene derivatives with appropriate reducing agents to form respective aniline derivatves.
- Reduction of Nitrobenzene (contd.)
- Preparation of Anilines (contd.)
- Reduction of Aromatic Nitro Compounds with Iron and Sodium Hydroxide
- Aromatic nitro compounds can be reduced to anilines by using a combination of iron and sodium hydroxide (Fe/NaOH).
- The reaction can be represented as:
ArNO2 + 6Fe + 12NaOH → ArNH2 + 6Fe(OH)3 + 6NaNO2 + 6H2O.
- Example: Reaction of aromatic nitro compound with Fe/NaOH to form aniline.
- Preparation of Anilines (contd.)
- Reduction of Aromatic Nitro Compounds with Hydrogen Sulphide
- Aromatic nitro compounds can also be reduced to anilines by using hydrogen sulfide (H2S).
- The reaction can be represented as:
ArNO2 + 3H2S + 2H2O → ArNH2 + 3H2SO4.
- Example: Reaction of aromatic nitro compound with H2S to form aniline.
- Preparation of Anilines (contd.)
- Reduction of Aromatic Nitro Compounds with Zinc and Sodium Hydroxide
- Aromatic nitro compounds can also be reduced to anilines by using zinc and sodium hydroxide (Zn/NaOH).
- The reaction can be represented as:
ArNO2 + Zn + 2NaOH → ArNH2 + Na2ZnO2 + H2O.
- Example: Reaction of aromatic nitro compound with Zn/NaOH to form aniline.
- Preparation of Anilines (contd.)
- Reduction of Aromatic Nitro Compounds with Hydrogen and a Catalyst
- Aromatic nitro compounds can be reduced to anilines by using hydrogen gas and a metal catalyst such as platinum, palladium, or nickel.
- The reaction takes place at high pressure and temperature.
- Example: Reaction of aromatic nitro compound with hydrogen (H2) and platinum catalyst to form aniline.
- Preparation of Anilines (contd.)
- Reduction of Aromatic Nitro Compounds with Sodium Hydroxide
- Aromatic nitro compounds can also be reduced to anilines by using sodium hydroxide (NaOH).
- The reaction can be represented as:
ArNO2 + 6NaOH + 4H2O → ArNH2 + 6NaNO3 + 9H2O.
- Example: Reaction of aromatic nitro compound with NaOH to form aniline.
- Preparation of Anilines (contd.)
- From Aryl Halides
- Anilines can be prepared by reducing aryl halides (halobenzenes) with a strong reducing agent like zinc and ammonium chloride (Zn/NH4Cl).
- The reaction can be represented as:
ArX + Zn + 2NH4Cl → ArNH2 + ZnCl2 + 2NH4X.
- Example: Reaction of aryl halide with Zn/NH4Cl to form aniline.
- Preparation of Anilines (contd.)
- From Diazonium Salts and Cuprous Chloride
- Anilines can be prepared by treating aryl diazonium salts with cuprous chloride (CuCl) in the presence of acids or acid salts.
- The reaction can be represented as:
ArN2+X- + CuCl → ArNH2 + CuX + N2.
- Example: Reaction of aryldiazonium salt with CuCl to form aniline.
- Preparation of Anilines (contd.)
- From Aryl Halides and Ammonia
- Anilines can also be prepared by heating aryl halides (halobenzenes) with ammonia (NH3) in the presence of a catalyst such as copper powder (Cu).
- The reaction can be represented as:
ArX + NH3 + Cu → ArNH2 + HX.
- Example: Reaction of aryl halide with NH3 and Cu to form aniline.
- Preparation of Anilines (contd.)
- From Phenols
- Anilines can be prepared by treating phenols with concentrated hydrochloric acid (HCl) or bromine (Br2) in the presence of a reducing agent like tin (Sn).
- The reaction can be represented as:
ArOH + HCl + Sn → ArNH2 + SnCl2 + H2O.
- Example: Reaction of phenol with HCl and Sn to form aniline.
- Preparation of Anilines (contd.)
- From Nitritic Acid and Sulfinic Acids
- Anilines can be prepared by subjecting aromatic compounds to the action of nitritic acid (HNO2) in the presence of sulfinic acids.
- The reaction can be represented as:
ArH + HNO2 + H2SO3 → ArNH2 + H2SO4.
- Example: Reaction of aromatic compound with HNO2 and H2SO3 to form aniline.
- Preparation of Anilines (contd.)
- From Aryl Halides and Toluene
- Anilines can be prepared by reacting aryl halides with toluene in the presence of a reducing agent like sodium hydroxide (NaOH).
- The reaction can be represented as:
ArX + C6H5CH3 + NaOH → ArNH2 + C6H5CH2ONa + HX.
- Example: Reaction of aryl halide with toluene and NaOH to form aniline.
- Preparation of Anilines (contd.)
- From Acetanilide
- Anilines can be prepared by reducing acetanilide with a strong reducing agent such as tin and hydrochloric acid (Sn/HCl).
- The reaction can be represented as:
CH3C6H4NHCOR + Sn + 4HCl → CH3C6H4NH2 + SnCl2 + CO2 + H2O + R.
- Example: Reaction of acetanilide with Sn/HCl to form aniline.
- Preparation of Anilines (contd.)
- From Cyanobenzene
- Anilines can be prepared by reducing cyanobenzene with a strong reducing agent like hydrogen gas and a metal catalyst such as platinum or palladium (H2/Pt or Pd).
- The reaction can be represented as:
C6H5CN + 2H2 + Pt or Pd → C6H5NH2 + H2O.
- Example: Reaction of cyanobenzene with H2/Pt or Pd to form aniline.
- Preparation of Anilines (contd.)
- From Benzene via Gabriel Synthesis
- Anilines can be prepared by using the Gabriel synthesis method.
- The reaction involves the use of potassium phthalimide (C8H5NO2K) followed by hydrolysis and decarboxylation steps.
- Example: Gabriel synthesis to form aniline.
- Preparation of Anilines (contd.)
- From Diazonium Salts and Phenols
- Anilines can be prepared by reacting aryldiazonium salts with phenols.
- The reaction can be represented as:
ArN2+X- + ArOH → ArNH2 + X- + ArO-.
- Example: Reaction of aryldiazonium salt with phenol to form aniline.
- Preparation of Anilines (contd.)
- From Peroxides
- Anilines can be prepared by reacting aromatic compounds with hydrogen peroxide (H2O2) in the presence of a catalyst like palladium on carbon.
- The reaction can be represented as:
ArH + H2O2 → ArNH2 + H2O.
- Example: Reaction of aromatic compound with H2O2 and palladium on carbon to form aniline.
- Preparation of Anilines (contd.)
- From Nitroso Compounds
- Anilines can be prepared by reducing nitroso compounds with a reducing agent like sodium bisulfate (NaHSO4) or sodium hydrosulfite (Na2S2O4).
- The reaction can be represented as:
ArN=O + NaHSO4 + 2H2O → ArNH2 + NaHSO3 + H2SO4.
- Example: Reaction of nitroso compound with NaHSO4 to form aniline.
- Preparation of Anilines (contd.)
- From Nitroso Compounds (contd.)
- Another method involves the use of ferrous sulfate (FeSO4) as a reducing agent.
- Example: Reaction of nitroso compound with FeSO4 to form aniline.
- Preparation of Anilines (contd.)
- From Nitroso Compounds (contd.)
- Anilines can also be prepared by reducing nitroso compounds using sodium sulfide (Na2S).
- Example: Reaction of nitroso compound with Na2S to form aniline.
- Summary
- Anilines can be derived from various starting materials including nitrobenzenes, aryl diazonium salts, phenols, acetanilide, and other aromatic compounds.
- Various reducing agents and catalysts can be employed to carry out the reduction reactions.
- The choice of the reducing agent and reaction conditions depends on the specific starting material and desired aniline derivative.
- Anilines are important compounds in organic synthesis and find extensive applications in the production of dyes, pharmaceuticals, and other chemical compounds.
Nitrogen Containing Organic Compounds - Preparation of Anilines Introduction Aniline is a nitrogen-containing organic compound with the chemical formula C 6 H 5 N. It is also known as aminobenzene, phenylamine, or benzenamine. Aniline is an important precursor for a variety of chemical compounds and dyes. In this lecture, we will discuss the preparation of anilines. Preparation of Anilines Reduction of Nitrobenzene Nitrobenzene can be reduced to aniline by using reducing agents such as iron and hydrochloric acid (Fe/HCl). The reaction can be represented as: C 6 H 5 NO 2 + 6H 2 → C 6 H 5 NH 2 + 2H 2 O. Example: Reaction of nitrobenzene with Fe/HCl to form aniline. Preparation of Anilines (contd.) Reduction of Nitrobenzene (contd.) Another method involves the use of tin and hydrochloric acid (Sn/HCl) as reducing agents. The reaction can be represented as: C 6 H 5 NO 2 + 3Sn + 6HCl → C 6 H 5 NH 2 + 3SnCl 2 + 2H 2 O. Example: Reaction of nitrobenzene with Sn/HCl to form aniline. Preparation of Anilines (contd.) Reduction of Nitrobenzene (contd.) Sodium sulfide (Na 2 S) can also be used as a reducing agent to convert nitrobenzene into aniline. The reaction can be represented as: C 6 H 5 NO 2 + 6Na 2 S + 4H 2 O → C 6 H 5 NH 2 + 6NaHSO 3 . Example: Reaction of nitrobenzene with Na 2 S to form aniline. Preparation of Anilines (contd.) Reduction of Nitrobenzene (contd.) Reduction can also be achieved using a catalyst such as platinum, palladium, or nickel. The reaction takes place in the presence of hydrogen gas (H 2 ). Example: Reaction of nitrobenzene with catalytic hydrogenation to form aniline. Preparation of Anilines (contd.) Reduction of Nitrobenzene (contd.) Alternatively, reduction of nitro compounds can be carried out using molecular hydrogen (H 2 ) and a metal catalyst such as Raney nickel or palladium on carbon. Example: Reaction of nitrobenzene with hydrogen (H 2 ) and Raney nickel catalyst to form aniline. Preparation of Anilines (contd.) Reduction of Nitrobenzene (contd.) Reduction using ammonium sulfide (NH 4 ) 2 S can also be employed to convert nitrobenzene into aniline. Example: Reaction of nitrobenzene with (NH 4 ) 2 S to form aniline. Preparation of Anilines (contd.) Reduction of Nitrobenzene (contd.) Aniline can also be prepared by the reduction of aryldiazonium salts with hypophosphorus acid. The reaction can be represented as: C 6 H 5 N 2 + X - + H 3 PO 2 → C 6 H 5 NH 2 + H 3 PO 3 + X - . Example: Reaction of aryldiazonium salt with hypophosphorus acid to form aniline. Preparation of Anilines (contd.) Reduction of Nitrobenzene (contd.) Aniline derivatives can also be obtained by the reduction of nitro compounds using various reducing agents. Example: Reduction of nitrobenzene derivatives with appropriate reducing agents to form respective aniline derivatves.