Organic Compounds Containing Nitrogen

Organic compounds containing nitrogen are a class of organic chemicals where nitrogen atoms are incorporated into the molecular structure. Nitrogen is a versatile element that can form stable bonds with carbon, hydrogen, and other elements, which allows it to participate in a wide range of organic compounds with varied properties and functions. In this article we will study types of nitrogen containing compounds.

1.0Types of Nitrogen Containing Compounds

Here is a list of organic compounds containing nitrogen

S.N.	Compound	Description	Structure
	Amines	Derivatives of ammonia where one or more hydrogen atoms are replaced by alkyl or aryl groups.	R-NH2
	Amides	Formed from an acid (usually carboxylic) and an amine
	Nitro Compounds	Contain one or more nitro groups (-NO2) attached to a carbon atom.
	Nitriles	Characterized by a carbon triple-bonded to a nitrogen atom (-C≡N)	R一C☰ N
	Azides	Containing the azide group (-N3)	R一N3
	Imines	Contains a double bond between carbon and nitrogen
	Pyridines and Pyrimidines	These are aromatic compounds containing nitrogen atoms within a ring structure.

Amines

Amines are derived from ammonia by replacing one or more hydrogen atoms with alkyl groups. They are categorized as primary, secondary, or tertiary based on the number of alkyl groups attached to the nitrogen atom.

General formula and Classification of Amines

Amines are classified based on the number of alkyl or aryl groups attached to the nitrogen atom. Here's a summary of their general formulas and types:

Primary Amines (RNH₂):

• General Formula: R−NH₂
• One alkyl or aryl group (R) is attached to the nitrogen atom, with two hydrogen atoms remaining.

Secondary Amines (R₂NH):

• General Formula:R₂−NH
• Two alkyl or aryl groups are attached to the nitrogen atom, with one hydrogen atom remaining.

Tertiary Amines (R₃N):

• General Formula:R₃−N
• Three alkyl or aryl groups are attached to the nitrogen atom, with no hydrogen atoms remaining.

Physical properties of Amines

Methods of Preparation of Amines

1. Ammonolysis of Alkyl Halides and Alcohols-

• From Alkyl Halides: When an aqueous solution of ammonia is heated with an alkyl halide, it can lead to the formation of all three types of amines (primary, secondary, and tertiary) as well as a quaternary ammonium salt.

• From Alcohols: When an alcohol (ROH) and Ammonia (NH₃) are passed over catalysts like aluminum oxide (Al₂O₃) or thorium dioxide (ThO₂) at 350°C, all three types of amines (primary, secondary, and tertiary) are produced.

2. Reduction of Amides (RCONH₂) and Nitriles (RCN)-

Amides can be reduced to primary amines through several methods, including:

1. Using reducing agents such as lithium aluminum hydride (LiAlH₄) which is one of the most common and effective methods. This reduction typically proceeds via the complete reduction of the amide
2. The addition of hydrogen (H₂) across the triple bond of the nitrile using a catalyst, typically palladium or nickel, under high pressure and temperature.

3.  Hofmann Bromamide Reaction- 

The Hofmann Bromamide Reaction, also known as Hofmann's Rearrangement, is a classical method used to convert amides into primary amines with one fewer carbon atom in the molecule.

This reaction involves the transformation of an amide (RCONH₂) into a primary amine (R-NH₂) where the resulting amine contains one carbon atom less than the starting amide

2.0Aniline (C₆H₅NH₂)

Aniline is an organic compound and one of the simplest aromatic amines. Aniline consists of a phenyl group (a benzene ring, C₆H₆) attached to an amino group (NH₂).

Physical Properties of Aniline

Chemical Properties of Aniline

Basicity: Aniline is a weak base. It is less basic than aliphatic amines because the lone pair of electrons on the nitrogen atom is delocalized into the benzene ring, reducing its availability to form bonds with protons.

• Aniline is a weak base but it forms salt with strong acids. It accepts a proton. Here are a few reactions

Reactivity: Aniline participates in a variety of chemical reactions, typical of aromatic amines. It undergoes electrophilic substitution reactions at the benzene ring, such as halogenation, nitration, and sulfonation. 

Alkylation of Aniline

Alkylation involves the addition of an alkyl group to the nitrogen atom of aniline. This is commonly achieved using alkyl halides in the presence of a base.

                                C₆H₅NH₂ + RX  ⟶  C₆H₅NHR  + HX

Where RX is an alkyl halide and HX is a hydrogen halide.

Acylation of Aniline-

Acylation of aniline involves its reaction with acid chlorides or anhydrides to form corresponding amides, known as anilides. 

A classic example of this reaction is the Schotten-Baumann reaction, where aniline (C₆H₅NH₂) reacts with benzoyl chloride to produce benzamide. This type of reaction showcases how aniline can be transformed into a variety of functionalized derivatives through the introduction of acyl groups.

General Methods of Preparation of Aniline

Aniline (C₆H₅NH₂) can be synthesized through several general methods. Mainly are lab method, Industrial method, preparation from Phenol, Benjamide and Benzoic acid. Reactions are- 

Test of Aniline

1. Carbylamine Test (Isocyanide Test)

Aniline undergoes the carbylamine test, which is used to detect primary amines. This test involves the reaction of aniline with chloroform and potassium hydroxide.

Reaction:

C₆H₅NH₂ + CHCl₃ + KOH  →  C₆H₅NC  +  KCl + H₂O

Observation:

• Aniline reacts to form phenyl isocyanide (C₆H₅NC), which has a strong, unpleasant smell. This characteristic odor is indicative of a positive test for primary amines.

2. Dye Test

Aniline can be used to produce a vibrant dye, a test that involves diazotization followed by coupling with an aromatic compound like β-naphthol.

• Steps of the test:
• • Diazotization: Aniline is treated with nitrous acid (generated in situ from sodium nitrite and hydrochloric acid) at low temperatures to form diazonium salt.
  • Coupling Reaction: The diazonium salt is then reacted with an alkaline solution of β-naphthol.

Observation:

• A red-orange dye is formed, indicating the presence of aniline. This test showcases aniline's ability to participate in azo dye formation.

3. Reaction with Bromine Water

Aniline reacts with bromine water to form a precipitate, which is a diagnostic reaction for aromatic amines.

• Reaction: C₆H₅NH₂  + 3Br₂  →   C₆H₂Br₃NH₂  + 3HBr

Observation:

• Upon adding bromine water to aniline, a white precipitate of 2,4,6-tribromoaniline is formed. This reaction is a straightforward test for the presence of aniline or other aromatic amines.

3.0Nitro Compounds

Organic compounds that feature a nitro group (-NO₂) as the functional group are known as nitro compounds. These compounds can be categorized into aliphatic or aromatic types, depending on the nature of the carbon chain to which the nitro group is attached.

Aliphatic Nitro Compounds

• In aliphatic nitro compounds, the nitro group is bonded to a saturated carbon atom that is part of an alkyl chain.
• They tend to be more reactive than their aromatic counterparts due to the less stable nature of the alkyl chain. Aliphatic nitro compounds are often used as solvents and precursors in organic synthesis.
• Example: Nitromethane (CH₃NO₂) is a simple aliphatic nitro compound used as a solvent and in fuel additives.

Aromatic Nitro Compounds

• Characteristics: Aromatic nitro compounds have the nitro group attached to an aromatic ring, such as a benzene ring.
• These compounds are generally more stable than aliphatic nitro compounds. The aromatic system provides resonance stabilization to the nitro group, making these compounds less reactive.
• Example: Nitrobenzene (C₆H₅NO₂) is a basic aromatic nitro compound used in the manufacture of aniline and as a precursor to various dyes and pharmaceuticals.

Preparation of Nitro Compounds

1. Nitration of Alkanes: Direct nitration using fuming nitric acid at 413K.
2. Nitration of Aromatic Compounds: Treatment of aromatic hydrocarbons with concentrated nitric acid and sulfuric acid to generate aromatic nitro compounds
3. Nitrosation Followed by Oxidation: Alkenes are first nitrosated with nitrous acid, then oxidized to form aliphatic nitro compounds.
4. Substitution of Halides: Alkyl or aryl halides react with nitrite salts, where the nitrite ion replaces the halide to form nitro compounds.

Here are some important reactions for Preparation of Nitro Compound: