Overview of Organic Compounds Containing Nitrogen

The compounds obtained by replacing the hydrogen atom of hydrogen cyanide (HCN) by an alkyl or aryl group through the carbon atom are called cyanides or nitriles.

The compounds obtained by replacing the hydrogen atom of hydrogen cyanide (HCN) by an alkyl or aryl group through the nitrogen atom are called isocyanides, isonitriles or carbylamines.

The functional group –C≡N present in cyanides is called the cyano group or nitrile group.

The functional group –N≡C present in isocyanides is called the isocyano group or isonitrile group.

A nucleophile that can attack through two different atoms (two reactive centres) is called an ambident nucleophile.

Cyanides containing an alkyl group attached to the –C≡N group are called alkyl cyanides.

Isocyanides containing an alkyl group attached to the –N≡C group are called alkyl isocyanides.

The reaction in which a primary amine when heated with chloroform and alcoholic KOH forms an isocyanide is called the carbylamine reaction.

The decarboxylation of sodium or potassium salts of carboxylic acids by electrolysis of their aqueous solution is called Kolbe’s electrolysis.

1. Hydrolysis of Cyanides (Nitriles): Cyanides on hydrolysis with acids or alkalis form an amide as intermediate and finally give a carboxylic acid and ammonia.
2. Hydrolysis of Isocyanides: Isocyanides are hydrolysed only by dilute acids (not by alkalis) to give a primary amine and formic acid.
3. Complete Reduction of Cyanides: On complete reduction (H₂/Ni or Pt, LiAlH₄, or Na + alcohol), cyanides are converted into primary (1°) amines.
   (This reduction with Na + alcohol is called Mendius reaction.)
4. Complete Reduction of Isocyanides: On complete reduction, isocyanides form secondary (2°) amines.
5. Partial Reduction of Cyanides (Stephen’s Reaction): Cyanides on reduction with SnCl₂ and HCl form imine hydrochloride, which on hydrolysis gives an aldehyde.
6. Reaction with Grignard Reagents: Cyanides react with Grignard reagents to form imine salts which on hydrolysis give ketones.
7. Addition Reactions of Isocyanides: Isocyanides (not cyanides) undergo addition reactions with halogens, ozone, sulphur, etc., forming addition products.
8. Rearrangement (Isomerisation): On prolonged heating, isocyanides rearrange to form the more stable cyanides.

1. Solubility in Water
   Lower aliphatic amines (up to about 6 carbon atoms) are soluble in water due to hydrogen bonding with water molecules.
2. Effect of Alkyl Group on Solubility
   Solubility of amines decreases with increase in size of alkyl group due to the hydrophobic nature of alkyl groups.
3. Aromatic Amines
   Aromatic amines are almost insoluble in water because weak hydrogen bonding cannot overcome the large hydrophobic benzene ring.
4. Boiling Points (General Order)
   Boiling points of amines are higher than hydrocarbons but lower than alcohols and carboxylic acids of comparable molecular mass.
5. Order of Boiling Points in Amines
   For isomeric amines:
   Primary (1°) > Secondary (2°) > Tertiary (3°)
   due to decreasing extent of intermolecular hydrogen bonding (tertiary amines lack N–H bonds).

An organic compound derived from ammonia by replacing one or more hydrogen atoms with alkyl or aryl groups is called an amine.

An amine in which one hydrogen atom of ammonia is replaced by an alkyl or aryl group is called a primary (1°) amine.

An amine in which two hydrogen atoms of ammonia are replaced by alkyl or aryl groups is called a secondary (2°) amine.

An amine in which all three hydrogen atoms of ammonia are replaced by alkyl or aryl groups is called a tertiary (3°) amine.

An amine in which the nitrogen atom is directly attached to one or more alkyl groups is called an aliphatic amine.

An amine in which the nitrogen atom is directly attached to an aromatic ring is called an aromatic amine.

An aromatic amine in which the nitrogen atom is directly bonded to the benzene ring is called an aryl amine.

An amine in which the nitrogen atom is attached to the side chain of an aromatic ring is called an arylakylamine (alkylarylamine).

The reaction in which an alkyl halide reacts with ammonia to form amines is called ammonolysis

The reduction of a nitrile using sodium and alcohol to form a primary amine is called the Mendius reaction.

The reaction in which a primary amide is treated with bromine and alkali to give a primary amine containing one carbon atom less is called the Hoffmann’s bromamide reaction (Hoffmann degradation).

The reaction in which an aldehyde or ketone reacts with ammonia followed by reduction to give an amine is called reductive amination.

The method of preparing primary amines by treating potassium phthalimide with an alkyl halide followed by hydrolysis is called the Gabriel phthalimide reaction.

The type of isomerism arising due to different carbon chain arrangements in amines having the same molecular formula is called chain isomerism.

The type of isomerism arising due to different positions of the amino group in amines having the same molecular formula is called position isomerism.

The type of isomerism arising due to different alkyl groups attached to the nitrogen atom in secondary and tertiary amines is called metamerism.

1. Reaction with Acids
   All amines are basic in nature and react with mineral acids (HCl, H₂SO₄, etc.) to form ammonium salts.
2. Reaction with Metal Ions
   Amines act as ligands and form soluble coordination complexes with metal ions like Ag⁺, Cu²⁺, etc.
3. Alkylation (Reaction with Alkyl Halides)
   Primary, secondary and tertiary amines react with alkyl halides to form higher amines and finally quaternary ammonium salts (exhaustive alkylation).
4. Acylation (Reaction with Acid Chlorides/Anhydrides)
   Primary and secondary amines react with acid chlorides or acid anhydrides to form amides, while tertiary amines do not undergo acylation.
5. Reaction with Nitrous Acid (HNO₂)
   Primary amines give alcohols (aliphatic) or diazonium salts (aromatic); secondary amines form nitrosamines; tertiary amines form ammonium nitrite salts.
6. Carbylamine Reaction
   Only primary amines (aliphatic and aromatic) react with chloroform and alcoholic KOH to form isocyanides (carbylamines) with a foul smell.
7. Reaction with Benzene Sulphonyl Chloride (Hinsberg Test)
   Primary, secondary and tertiary amines react differently with benzene sulphonyl chloride, and this reaction is used to distinguish between the three types of amines.

1. Physical Nature: Aniline is a colourless oily liquid with faint odour, sparingly soluble in water, steam volatile and easily oxidised in air to become dark coloured.
2. Basic Nature: Aniline is a weak base and is less basic than ammonia and aliphatic amines due to resonance involving the –NH₂ group and benzene ring.
3. Salt Formation: Aniline reacts with strong acids like HCl and H₂SO₄ to form water-soluble anilinium salts.
4. Acylation and Benzoylation: Aniline reacts with acid chlorides/anhydrides to form amides (anilides), and with benzoyl chloride in NaOH (Schotten–Baumann reaction) to form benzanilide.
5. Diazotisation: Aniline reacts with nitrous acid (NaNO₂ + HCl) at 273–278 K to form benzene diazonium chloride.
6. Carbylamine Reaction: Being a primary amine, aniline reacts with chloroform and alcoholic KOH to form phenyl isocyanide (offensive smell), which is used as a test for primary amines.
7. Electrophilic Substitution: The –NH₂ group is an activating, ortho-para directing group; therefore, aniline undergoes electrophilic substitution mainly at o- and p-positions (often giving 2,4,6-substituted products unless protected by acetylation).