Aniline is an aromatic amine with a chemical formula of -C 6 H 5 NH 2 . A benzene group attached to a -NH 2 group is called aniline.

Anilines (C6H5NH2) - Formula, Preparation, Structure, Properties, FAQs

Q: Show how p-methoxy aniline is stronger base as compared to aniline.

-OCH 3 group is electron releasing group release the electrons and increases the basic strength of aniline.

Edited By Team Careers360 | Updated on Jul 02, 2025 04:51 PM IST

After reading this article, the reader should be able to understand- Aniline formula, Aniline Structure, resonating structure of aniline, density of aniline, melting point of aniline, boiling point of aniline.

Aniline

Aniline is the simplest organic compound that is an aromatic benzene with the chemical formula- C₆H₅-NH₂

Aniline is an aromatic amine in which an amine group (-NH₂) is attached to a benzene group. Therefore, The Functional group of Aniline is amino group.

Aniline boiling point-	184.1⁰C
Aniline density-	1.02 g/cm³
Aniline Melting point-	-6.3⁰C

Aniline structural formula is shown below-

aniline

Structure of aniline- If you take out one hydrogen from ammonia and attach a benzene group with it, it gives us the structure of aniline. Aniline molecular formula is C₆H₇N and chemical formula is C₆H₅-NH₂
The molecular weight of aniline is 93 g/mol (12×6 Carbons+7×1Hydrogens+14×1Nitrogen)
Aniline is an unsaturated compound due to the presence of an unsaturated benzene ring. Unsaturation arises due to bonds other than sigma and Benzene has three pi bonds.

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Aniline
Resonance structure of aniline
Preparation of aniline-
Reactions of Aniline-
Aniline uses-

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Nomenclature of Aniline-

The General common name for all the aromatic amine is aryl amine.
IUPAC name for aromatic amine is benzenamine. For ex- Aniline IUPAC name is benzenamine because aniline is the simplest aromatic amine.
Aniline and benzylamine are two different compounds. Aniline is an aromatic amine however, benzylamine is an aliphatic amine which means amine is not directly attached to an aromatic system in benzylamine.

Physical properties of aromatic amines-

Aromatic amines are generally toxic.
Aniline color in pure form is colorless, however on oxidation and addition of impurities they start to impart a certain color.

Isomerism in Aniline-

Aromatic amine can show position isomerism when another group such as methyl or nitro group are introduced on the benzene ring. The positions of these groups can change in position with respect to amine group.
Ortho, para and meta are three positions for amine group with respect to methyl. All these three structures will give position isomers of aniline.

Basicity of Aniline-

Aniline contains one nitrogen which has one lone pair of electrons which determines aniline nature. Nitrogen forms three bonds in total and rest of the two electrons exist as lone pair.
Lone pair accounts for the basic nature of all nitrogen-containing compounds. However, there can be other factor that can increase or decrease the basicity of a compound.
For ex- ethylamine and aniline are both Nitrogen-containing compounds. However, ethylamine is more basic than aniline. This is because in case of aniline the lone pair is not available for donation as it participates in conjugation. In Structure 3,4, and 5 there is a positive charge on nitrogen atom hence due to resonance aniline becomes less basic due to resonance.
These electrons interact with the pi system of benzene ring and resonating structures are obtained.
Aniline resonance is due to the Resonating structure of aniline a

Resonance structure of aniline

Anilinium ion- This ion is formed after the Amine group attached to benzene group gets protonated and nitrogen acquires a positive charge. The resonating structures for this ion are only two and we know the more is the number of resonating structures more is the stability of that compound.

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Resonating structure of Anilinium ion-

Preparation of aniline-

A variety of substrates of are used to synthesize aniline such as alkyl halides, nitro groups, nitriles, amides, benzamides, and benzoic acid.

Alkyl halides-

Nucleophilic substitution reaction of ammonia on alkyl halides takes place at 373 K in a sealed tube. An ammonium salt is formed which reacts with a base to form primary amine.

RX+NH₃→RNH₃⁺X^-

RNH₃⁺X^- + NaOH→RNH₂+ H₂O+NaX

Amides-

Amides undergo reduction in the presence of lithium aluminium hydride. The number of carbon atoms are same as the original amide.

cacid

Carboxylic acid -

Carboxylic acids are used to synthesize primary amines in the presence of hydrazoic acid.

nitro%20compund

Nitro compounds-

Nitro compounds get reduced in the presence of acid and active metals such as zinc, iron, and tin.

2h2o

However, on an industrial scale the best method for the production of aniline is the catalytic hydrogenation of nitrobenzene by hydrogen in the presence of platinum.
Few other known methods for the synthesis of aniline are by the treatment of chlorobenzene with ammonia at 473 k and a pressure of 60 atm pressure.

Reactions of Aniline-

Reaction with acid-

Due to the presence of lone pair on nitrogen aniline behaves as basic in nature. Anilinium hydrochloride is the product that is formed. If a strong base is added, then aniline can be liberated.

Aniline HCl reaction is shown as following-

hcl

Acylation- Benzenamine reacts with acetyl chloride in the presence of base such as pyridine to form analide. A hydrogen group of -NH₂ is replaced with

–RCO group. The presence of base is necessary for the removal of Cl of acid chloride. Base should be stronger than ammonia to shift the equilibrium to the right side of the reaction.

Analide formula is N- Phenyl ethanamide or acetanilide.

Analide structure is shown below-

anilen%20structure

Related Topics Link,

Alkylation of aniline-

It is possible to introduce a methyl group onto the nitrogen atom of -NH2 group by the removal of Hydrogen. An alkyl halide is introduced for the nucleophilic substitution reaction. Here the amine will act as nucleophile and alkyl halide performs the attack.

htl

Oxidation of Aniline-

Oxidation of amines depend upon their structure as well as the selected oxidizing agent. Many different types of oxidizing agents are used like Caro’s acid, hydrogen peroxide, potassium permanganate etc.

Eg- Potassium permanganate-

RH₂ [o]→ RNHOH [o]→ R-N=O [o]→ R-NO₂

Also read :

Aniline uses-

Aniline is a crucial raw material for the synthesis of many industrial products such as polymers, pesticides, paracetamol, rubber and dyes.

Aniline polymerization-

Polymer of aniline is a conducting polymer. PANI is the polymer of aniline. All the monomer units of polyaniline are arranged in a head-to-toe manner.

Polyaniline structure is a stable structure due to strong stabilizing agents such very strong acids.

Synthesis-

Aniline polymerization is shown as follows-

nh4

Polyaniline properties help in production of colored electrically conductive products, formation of plastic batteries and photovoltaic cells.

Aniline oil- is used in formation of dyes and medicines.

Anisole structure

Anisole structure

Anisole IUPAC name

Anisole IUPAC name is methoxybenzene.

Pentyne structure

Pentyne structure

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NCERT Chemistry Notes :

Frequently Asked Questions (FAQs)

1. Why Anthranilic acid does not exist as Zwitter ion?

In anthranilic acid, benzene acts as electron withdrawing group that depresses the tendency of weak acidic group (-COOH) to donate its proton to amine -NH₂ group. Whereas, in case of aliphatic chains for ex- glycine can exist as zwitter ion.

2. Explain what is aniline point?

Aniline point is a measure of miscibility of lubricating oils with aniline when the volumes of aniline is equal to other lubricating oils.

3. Is aniline saturated or unsaturated?OCH3

Aniline is an unsaturated compound due to the presence of benzene ring. Benzene has three double bonds and these Double bonds make a compound unsaturated.

4. How to form aniline to benzonitrile?

Aniline is converted to Diazonium salt. Diazonium salt is further converted to benzonitrile.

5. What is aniline?

Aniline is an aromatic amine with a chemical formula of -C₆H₅NH₂. A benzene group attached to a -NH₂ group is called aniline.

6. Show how p-methoxy aniline is stronger base as compared to aniline.

-OCH₃ group is electron releasing group release the electrons and increases the basic strength of aniline.

7. What is the molecular formula of aniline?

The molecular formula of aniline is C6H5NH2. It consists of a benzene ring (C6H5) bonded to an amino group (NH2).

8. Why is aniline considered an aromatic amine?

Aniline is considered an aromatic amine because it contains an amino group (-NH2) directly attached to a benzene ring. The presence of the aromatic ring gives aniline its characteristic properties and reactivity.

9. How does the structure of aniline differ from aliphatic amines?

Aniline has a benzene ring attached to the amino group, while aliphatic amines have their amino group attached to alkyl chains. This structural difference leads to distinct chemical and physical properties between aromatic and aliphatic amines.

10. What is the boiling point of aniline, and how does it compare to similar-sized alkanes?

Aniline has a boiling point of about 184°C, which is significantly higher than similar-sized alkanes. This elevated boiling point is due to hydrogen bonding between aniline molecules, requiring more energy to overcome these intermolecular forces during vaporization.

11. How does the solubility of aniline in water compare to that of benzene?

Aniline is slightly soluble in water, while benzene is practically insoluble. This difference is due to the presence of the polar amino group in aniline, which can form hydrogen bonds with water molecules, enhancing its solubility compared to non-polar benzene.

12. What is the significance of aniline in the dye industry?

Aniline is a crucial starting material for many synthetic dyes, particularly azo dyes. Its ability to undergo various reactions, including diazotization, makes it valuable in producing a wide range of colored compounds used in textiles, paints, and other applications.

13. What is the importance of aniline in the pharmaceutical industry?

Aniline and its derivatives are important in the pharmaceutical industry as precursors for various drugs. Many pharmaceuticals contain aniline-derived structures, including analgesics, antihistamines, and antibiotics. However, aniline itself is not used directly due to its toxicity.

14. What is the significance of the diazonium salt derived from aniline?

The diazonium salt derived from aniline is a versatile intermediate in organic synthesis. It can undergo various reactions, including azo coupling to form azo dyes, replacement of the diazonium group with other functional groups (e.g., -OH, -CN, -I), and reduction to form aryl hydrazines.

15. What is the role of aniline in the production of polyurethanes?

Aniline is a key precursor in the production of methylene diphenyl diisocyanate (MDI), which is a crucial component in the manufacture of polyurethanes. Aniline is first converted to 4,4'-methylenedianiline (MDA), which is then phosgenated to produce MDI.

16. What is the environmental concern associated with aniline?

Aniline is a toxic compound and a potential environmental pollutant. It can be harmful to aquatic life and may contaminate soil and water sources. Aniline's ability to be absorbed through the skin and its potential carcinogenicity make it a significant environmental and occupational health concern.

17. What is the main industrial method for preparing aniline?

The main industrial method for preparing aniline is the catalytic reduction of nitrobenzene. This process typically uses hydrogen gas and a metal catalyst, such as palladium on carbon or Raney nickel.

18. How does the reduction of nitrobenzene to aniline occur?

The reduction of nitrobenzene to aniline involves the conversion of the nitro group (-NO2) to an amino group (-NH2). This is typically a six-electron reduction process, where three hydrogen molecules (H2) are consumed for each nitrobenzene molecule reduced.

19. What is the Hofmann rearrangement, and how is it related to aniline?

The Hofmann rearrangement is a reaction where an amide is converted to a primary amine with one fewer carbon atom. While not directly involving aniline, this rearrangement can be used to synthesize aniline from benzamide. The reaction involves treating benzamide with bromine and sodium hydroxide, followed by hydrolysis.

20. What is the difference between aniline and phenylamine?

There is no difference between aniline and phenylamine; they are two names for the same compound (C6H5NH2). Aniline is the common name, while phenylamine is the systematic name, indicating an amino group attached to a phenyl (benzene) ring.

21. How does aniline participate in the Sandmeyer reaction?

In the Sandmeyer reaction, aniline is first converted to a diazonium salt, which then undergoes nucleophilic substitution with various nucleophiles in the presence of copper salts. This reaction is used to introduce halogens (except fluorine), cyano groups, or hydroxyl groups into the aromatic ring, replacing the amino group of aniline.

22. How does aniline react with acids?

Aniline reacts with acids to form anilinium salts. The lone pair on the nitrogen atom accepts a proton from the acid, creating a positively charged anilinium ion. For example, aniline reacts with hydrochloric acid to form anilinium chloride (C6H5NH3+Cl-).

23. How does aniline participate in electrophilic aromatic substitution reactions?

Aniline readily undergoes electrophilic aromatic substitution reactions. The amino group is a strong activating group, directing incoming electrophiles to the ortho and para positions of the benzene ring. This high reactivity is due to the electron-donating nature of the amino group.

24. What is the color of pure aniline, and why does it change over time?

Pure aniline is a colorless liquid, but it tends to darken to a brown color when exposed to air and light. This color change is due to oxidation reactions that form various colored compounds, including quinone-like structures.

25. How does the reactivity of the amino group in aniline compare to that in aliphatic amines?

The amino group in aniline is less reactive than in aliphatic amines due to the partial delocalization of the nitrogen lone pair into the benzene ring. This reduces the nucleophilicity and basicity of aniline compared to aliphatic amines.

26. What is the pKa of anilinium ion, and how does it compare to ammonium ion?

The pKa of the anilinium ion is about 4.6, while the pKa of the ammonium ion is about 9.2. This indicates that aniline is a much weaker base than ammonia, primarily due to the resonance effect that delocalizes the nitrogen lone pair in aniline.

27. What is the hybridization of the nitrogen atom in aniline?

The nitrogen atom in aniline is sp3 hybridized. However, due to resonance with the benzene ring, the lone pair on nitrogen is partially delocalized, giving it some sp2 character.

28. How does the presence of the benzene ring affect the basicity of aniline compared to aliphatic amines?

Aniline is less basic than aliphatic amines because the lone pair on the nitrogen atom is partially delocalized into the benzene ring through resonance. This makes the lone pair less available for protonation, reducing aniline's basicity.

29. What is the resonance structure of aniline, and how does it affect its properties?

Aniline has several resonance structures where the lone pair on nitrogen is delocalized into the benzene ring. This resonance increases electron density in the ortho and para positions, enhancing reactivity at these sites and stabilizing the molecule. It also reduces the basicity of aniline compared to aliphatic amines.

30. How does the presence of aniline affect the pH of water?

When aniline is dissolved in water, it slightly increases the pH, making the solution weakly basic. This is because aniline acts as a weak base, accepting protons from water molecules to form anilinium ions and hydroxide ions.

31. How does aniline react with bromine water?

Aniline reacts rapidly with bromine water to form 2,4,6-tribromoaniline as the main product. The reaction occurs even without a catalyst due to the highly activated nature of the benzene ring in aniline. The bromine atoms substitute at the ortho and para positions relative to the amino group.

32. How can aniline be converted into a diazonium salt?

Aniline can be converted into a diazonium salt through a diazotization reaction. This involves treating aniline with nitrous acid (typically generated in situ from sodium nitrite and hydrochloric acid) at low temperatures (0-5°C). The resulting product is a benzenediazonium chloride salt.

33. How can aniline be distinguished from phenol in a chemical test?

Aniline can be distinguished from phenol using the azo dye test. Aniline forms a colored azo dye when treated with sodium nitrite and hydrochloric acid (to form diazonium salt) followed by coupling with β-naphthol. Phenol does not form a diazonium salt and thus doesn't produce an azo dye in this test.

34. How does aniline react with acetyl chloride?

Aniline reacts with acetyl chloride to form N-phenylacetamide (acetanilide). This is a nucleophilic acyl substitution reaction where the amino group of aniline acts as a nucleophile, attacking the carbonyl carbon of acetyl chloride. The reaction produces HCl as a byproduct.

35. How does the presence of substituents on the benzene ring affect the basicity of aniline derivatives?

Electron-donating substituents (e.g., -CH3, -OCH3) on the benzene ring increase the basicity of aniline derivatives by increasing electron density on the nitrogen atom. Conversely, electron-withdrawing groups (e.g., -NO2, -COOH) decrease basicity by reducing electron density on nitrogen.

36. What is the mechanism of the reaction between aniline and chloroform in the presence of alcoholic KOH?

This reaction, known as the Reimer-Tiemann reaction, involves the formation of isonitrile (phenyl isocyanide) as an intermediate. The chloroform is deprotonated by KOH to form a carbene, which reacts with the aniline's amino group. Subsequent steps lead to the formation of phenyl isocyanide, which hydrolyzes to form formanilide.

37. How can aniline be oxidized, and what are the products?

Aniline can be oxidized using various oxidizing agents. Mild oxidation with sodium dichromate in dilute sulfuric acid produces quinone. Stronger oxidation can lead to the cleavage of the benzene ring, forming maleic acid and other products. Careful oxidation can also produce nitrobenzene.

38. What is the role of aniline in the synthesis of sulfa drugs?

Aniline is a key starting material in the synthesis of sulfa drugs. It is first acetylated to form acetanilide, which is then sulfonated. The resulting p-acetamidobenzenesulfonyl chloride is reacted with various amines to produce different sulfa drugs, which are important antibacterial agents.

39. How does aniline react with nitrous acid at room temperature?

At room temperature, aniline reacts with nitrous acid to form diazonium salt (benzenediazonium chloride). This reaction, called diazotization, is typically carried out at 0-5°C to prevent decomposition of the unstable diazonium salt. At higher temperatures, the diazonium salt may decompose to form phenol.

40. What is the difference in reactivity between the amino group in aniline and the hydroxyl group in phenol?

The amino group in aniline is more nucleophilic than the hydroxyl group in phenol. This makes aniline more reactive in nucleophilic addition and substitution reactions. However, the hydroxyl group in phenol is more acidic, making phenol more reactive in certain electrophilic aromatic substitution reactions.

41. How does aniline behave as a ligand in coordination compounds?

Aniline can act as a monodentate ligand in coordination compounds, binding to metal ions through the lone pair on the nitrogen atom. However, it is generally a weaker ligand compared to aliphatic amines due to the partial delocalization of the nitrogen lone pair into the benzene ring.

42. What is the significance of aniline in the production of rubber chemicals?

Aniline is an important precursor in the production of various rubber chemicals, particularly antioxidants and antiozonants. For example, N-phenyl-2-naphthylamine, an antioxidant used in rubber, is synthesized from aniline. These additives help protect rubber products from degradation due to oxidation and ozone exposure.

43. How does the presence of aniline affect the conductivity of an aqueous solution?

The presence of aniline slightly increases the conductivity of an aqueous solution. Although aniline is a weak base and doesn't dissociate significantly, it does produce a small concentration of anilinium and hydroxide ions, which contribute to the solution's conductivity.

44. What is the role of aniline in the production of isocyanates?

Aniline is a key precursor in the production of isocyanates, particularly methylene diphenyl diisocyanate (MDI). Aniline is first reacted with formaldehyde to form methylenedianiline (MDA), which is then reacted with phosgene to produce MDI. Isocyanates are crucial components in the production of polyurethanes.

45. How does the presence of aniline affect the freezing point of water?

When aniline is dissolved in water, it lowers the freezing point of the solution. This is a colligative property that depends on the number of dissolved particles. Since aniline doesn't dissociate significantly in water, its effect on freezing point depression is less pronounced compared to ionic compounds.

46. What is the difference between aniline and N-methylaniline in terms of structure and properties?

N-methylaniline (C6H5NHCH3) has a methyl group attached to the nitrogen atom, while aniline (C6H5NH2) does not. This structural difference leads to several property changes: N-methylaniline is slightly more basic, less water-soluble, and has a lower melting point than aniline. It also exhibits different reactivity in some reactions, such as diazotization.

47. How does aniline react with alkyl halides?

Aniline reacts with alkyl halides through nucleophilic substitution, where the nitrogen atom acts as a nucleophile. This reaction can form N-alkylanilines (secondary amines) and, if excess alkyl halide is present, N,N-dialkylanilines (tertiary amines). The reaction often requires heating and may produce a mixture of products.

48. What is the Gabriel synthesis, and how is it related to aniline?

The Gabriel synthesis is a method for preparing primary amines, including aniline derivatives. While not used to synthesize aniline itself, it can be used to prepare substituted anilines. The process involves reacting potassium phthalimide with an alkyl halide, followed by hydrazinolysis to yield the primary amine.

49. How does aniline behave in a Friedel-Crafts alkylation reaction?

Aniline does not typically undergo Friedel-Crafts alkylation under standard conditions. The amino group strongly activates the ring towards electrophilic aromatic substitution, but it also coordinates strongly with the Lewis acid catalyst (e.g., AlCl3), inhibiting the reaction. Additionally, the basic nature of aniline can neutralize the acid catalyst.

50. What is the role of aniline in the synthesis of indigo dye?

Aniline is a precursor in one method of synthesizing indigo dye. In this process, aniline is first N-phenylated to form N-phenylaniline (diphenylamine). This is then reacted with chloroacetic acid to form phenylglycine-o-carboxylic acid, which can be converted to indoxyl. Oxidation of indoxyl