Organic Chemistry

Introduction of Amines

Interpretation of amine: A product in which one or more hydrogen atoms in an ammonia molecule are replaced by a hydrocarbon group, called an amine. Introduction of Amines

Introduction of Amines

According to the number of hydrogen atoms in the amine molecule, the amine can be divided into primary, secondary, and tertiary amines; a compound formed by substituting hydrogen in a molecule with a hydrocarbon group.

At the same time, the amine may be a derivative in which H in the ammonia molecule is substituted by a hydrocarbon group. The amine is widely present in the biological world and has extremely important physiological activities and biological activities.

Such as Proteins, nucleic acids, many hormones, antibiotics, and alkaloids are all complex derivatives of amines. Most of the drugs used in clinical practice are also amine or amine derivatives. Therefore, the nature and synthesis of amines are to study these complex natural products and better maintain the foundations of human health.

Classification of amines

According to the number of hydrogen substitutions, it is divided into primary amine (primary amine) RNH 2 and secondary amine (secondary amine) R 2 NH.

Tertiary amine (tertiary amine) R 3 N, quaternary ammonium salt (quaternary ammonium salt) R 4 N + X  , such as methylamine CH 3 NH 2, aniline C 6 H 5 NH 2 , ethylenediamine H2NCH2CH2NH 2, diisopropylamine [(CH3)2CH]2NH, triethanolamine (HOCH2CH2)3N, tetrabutylammonium bromide (CH3CH2CH2CH2)4N+Br .

Naming Compounds

A tetra hydroxyl substitution of ammonium hydroxide or ammonium salt is called a quaternary ammonium hydroxide or a quaternary ammonium salt.  NH +ammonium R 4 NOH quaternary ammonium base R 4 NX quaternary ammonium salt.

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The amine can be classified into a fatty amine and an aromatic amine depending on the kind of the hydroxyl group attached to the nitrogen atom in the amine molecule. If the amine molecule contains two or more amino groups (—NH 2), it can be classified into a diamine or a triamine according to the number of amino groups.

Physicochemical properties

At normal temperature, the lower aliphatic amine is a gas, the propylamine is a liquid, and the higher fatty amine is solid. Lower amines have an unpleasant or unpleasant smell. Introduction of Amines

For example, trimethylamine has a fishy smell, butadiamine (putrescine) and pentamethyleneamine (cadaverine) have a foul smell after the decay of animal carcasses. Higher amines are less volatile and have a low odor. Aromatic amines are high-boiling liquids or low-melting solids. Although they have a lower odor than fatty amines, they are more toxic.

They can cause poisoning by inhaling their vapors or by contacting them with skin. Some aromatic amines, such as β-naphthylamine and benzidine, are also carcinogenic.

Amines Structures

Since the nitrogen atom in the amine molecule can form a hydrogen bond with water, the solubility of the lower aliphatic amine in water is relatively large.

Primary and secondary amines can form intermolecular hydrogen bonds, but since the electronegativity of nitrogen atoms is less than that of oxygen atoms, the hydrogen bond association ability of amines is relatively weak, and its boiling point is lower than that of alcohols having similar molecular weights.

The amine is similar to ammonia, and the nitrogen atom in the molecule contains unshared electron pairs, which can be combined with H + to be alkaline.

R-NH 2 +HCl≒R-NH + Cl 

The basicity of the amine is represented by the basic ionization constant Kb or other negative logarithm value pKb. The larger the Kb value or the smaller the pKb value, the stronger the basicity of the amine.

Amine synthesis

Ammoniation of halides

There is a lone pair of electrons on the ammonia or amine nitrogen, and the nucleophilic reaction with the alkyl halide as a nucleophilic reagent is carried out according to the SN2 mechanism. Many organic halides are treated with ammonia or ammonia to form amines:

X is halogen

RX + NH 3 → RNH 3 + X 

RNH 3 +X  → RNH 2 + H 2 O + X 

Prepared with alcohol

The main synthesis of amines is the alkylation of ammonia. Industrial use of alcohols and ammonia to synthesize organic amines:

ROH + NH 3 → RNH 2 + H 2 O

These reactions require the use of catalysts, special equipment, and additional purification because a mixture of amines of the first, second, and third grades is obtained, and the selectivity of the reaction needs to be increased.

Amine production method

Amines are widely distributed in nature, most of which is produced by decarboxylation of amino acids. E.g:

The industrial method for preparing amines is mostly prepared by reacting ammonia with an alcohol or an alkyl halide, and the product is a mixture of amines at various stages and fractionated to obtain a pure product.

The corresponding amine can also be obtained by catalytic reduction of an aldehyde or a ketone in the presence of ammonia. Industrially, an amine compound is also often produced by catalytic reduction of a nitro compound, a nitrile, an amide or a nitrogen-containing heterocyclic compound. E.g:

Amine application

Amines are very versatile. The earliest developed dye industry was based on aniline. Some amines are required for life-sustaining activities.Introduction of Amines

However, some are very harmful to life. Many amine compounds have carcinogenic effects, especially aromatic amines such as naphthylamine and benzidine.


The name of a simple amine, with an amine as a functional group, called an amine, first writes the name of the hydroxyl group attached to the nitrogen atom, and then uses the amine word as the ending; the primary amine of the diamine and polyamine, when the amino group is attached to the open chain When a hydroxyl group is directly attached to a benzene ring, it may be referred to as a diamine or a triamine.

More complex amines can be termed as hydrocarbon derivatives. Quaternary ammonium compounds can be termed as ammonium derivatives.

The quaternary amine compound can be referred to as a derivative of an amine.

Amine structure

The structure of the nitrogen atom in the amine is much like the nitrogen atom in the ammonia molecule. It is connected to hydrogen or a hydrocarbon group by three sp hybrid orbitals to form a pyramid, leaving an sp3 hybrid orbital occupied by a lone pair. If an amine has three different groups, there should be a pair of enantiomers (see Enantiophage):

However, since the activation energy required for the lone pair of electrons in the flip-flop molecule is low, the enantiomer cannot be separated. Introduction of Amines

Experiments have shown that the amine and ammonia molecules have a prismatic structure, the nitrogen atom is an sp3 hybrid, and the bond angle is about 109 degrees.


In the amine molecule, the three sp3 hybrid orbitals overlap the s orbitals of the hydrogen atoms or the hybrid orbitals of the carbon atoms to form three 6-bonds, leaving a pair of lone pairs of electrons occupying the fourth sp3 orbital, located in the vertebral body. Introduction of Amines

Aniline is also a pyramidal structure, but the HNH bond angle is large, 113.9 degrees, and the angle between the NNH plane and the benzene ring plane is 38 degrees.

If the amine molecule has three different groups attached to the nitrogen atom, it is chiral, and theoretically, a pair of enantiomers should be present.

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Since the energy barrier between the two enantiomers is relatively low, about 21 KJ/mol, they can be rapidly converted to each other at room temperature, and in fact, such an enantiomer has not been separated.

In the quaternary ammonium salt, all four sp3 orbitals of nitrogen are used to form a bond, and if four different groups are attached to the nitrogen atom, an enantiomer is present. For example, methyl isopropyl phenyl benzylamine iodide is split into right-handed and left-handed optical isomers.

Several common amines

Methylamine: CH 3 NH 2

Nature: Also known as monomethylamine, it is a colorless, ammonia-smelling gas or liquid at normal temperature. It is flammable and its vapor can form an explosive mixture with air. The explosion limit is 5%-21% (4.95%-20.75%).

The relative density is 0.662, the melting point is -93.5 ° C, the boiling point is -6.3 ~ -6.7 ° C, -19.7 ° C (53.3 kPa), -32.4 ° C (26.7 kPa), -43.7 ° C (13.3 kPa), -73.8 ° C (1.33 kPa) , decomposition temperature 250 ° C, flash point (closed cup) 0 ° C, self-ignition point 430 ° C, vapor pressure (25 ° C) 202.65 Pa, critical temperature 156.9 ° C, critical pressure 4.073 kPa, refractive index 1.351. The smouldering body is more alkaline than ammonia. Soluble in water, ethanol, and ether.

Ethylamine: CH 3 CH 2 NH 2

Colorless liquid or gas with strong ammonia smell; vapor pressure 53.32kPa/20°C; flash point: <-17.8°C; melting point-80.9°C; boiling point 16.6°C; solubility: soluble in water, ethanol, ether, etc.; Relative density (water = 1) 0.70; relative density (air = 1) 1.56; stability: stable; hazard label 4 (flammable gas), 14 (with drugs); main use: for dye synthesis and as extractant, Emulsifiers, pharmaceutical raw materials, reagents, etc.

First, health hazards

Routes of entry: inhalation, ingestion, percutaneous absorption. Introduction of Amines

Health hazards: Exposure to ethylamine vapor can cause eye irritation, corneal damage, and upper respiratory tract irritation. Liquid splashing into the eyes can cause serious low-level injuries; contaminated skin can cause burns.

Second, emergency treatment and disposal methods

 1. Leakage emergency treatment

Quickly evacuate people from the contaminated area to the upper reaches, and isolate them, strictly restricting access. Cut off the fire source. It is recommended that emergency personnel wear self-contained positive pressure breathing apparatus and wear fire protective clothing.  Introduction of Amines

Cut off the source of the leak as much as possible. In the case of gas, cover the sewers near the leak point with an industrial coating or an absorbent/absorbent to prevent gas from entering. Proper ventilation and accelerated diffusion. The sprayed water is diluted and dissolved.


Construct a large amount of wastewater generated by dikes or digging pits. If possible, send the residual gas or leaking air to the washing tower or the fume hood connected to the tower. The leaking container should be properly disposed of, repaired, and used after inspection.

If liquid, absorb with sand, vermiculite or other inert materials. If there is a large amount of leakage, construct a dike or digging pit; cover with foam to reduce the steam disaster. Transfer to a tank truck or special collector with an explosion-proof pump, recycle or transport to a waste disposal site for disposal. It is best to have a dilute acid spraying facility in the tank area. Introduction of Amines

Waste disposal method: Controlled incineration method. The nitrogen oxides emitted from the incinerator are removed by a scrubber or a high-temperature device.

2, protective measures

Respiratory protection: Wear a filter-type gas mask (half mask) when the concentration in the air exceeds the standard. Oxygen breathing apparatus or air breathing apparatus is recommended for emergency rescue or evacuation.

Eye protection: Wear chemical safety glasses.

Body protection: Wear tape anti-virus clothing.

Hand protection: Wear rubber gloves.

Other: Smoking, eating, and drinking are strictly prohibited on the job site. After work, take a shower and change clothes.

3, first aid measures

Skin contact: Immediately remove contaminated clothing and rinse with plenty of running water for at least 15 minutes. Seek medical attention.

Eye contact: Immediately lift eyelids and rinse thoroughly with plenty of running water or saline for at least 15 minutes. Seek medical attention.

Inhalation: Remove quickly from the scene to fresh air. Keep the airway open. If breathing is difficult, give oxygen. If breathing stops, perform artificial respiration immediately. Seek medical attention.

Ingestion: Inadvertently gargle with water, give milk or egg white. Seek medical attention.

Firefighting method: cut off the air source. If the gas source cannot be shut off immediately, it is not allowed to extinguish the burning gas. Spray the water to cool the container and, if possible, move the container from the fire to the open space. Extinguishing media: water spray, anti-solvent foam, dry powder, carbon dioxide.


H – N – H    +     R / Ar     ——->          H – N – R/Ar
|                                                                         |
H                                                                       H

5. Gabriel Phthalimide:-

Gabriel Phthalimide से केवल Aliphatic Amines ही बनती हैं! जैसे की image में बताया गया हैं!

6. Hoffmann Bromamide Reaction:-

जब amide group की reaction Br 2 + KOH से करायी जाती है तो amine प्राप्त होता हैं! इस reaction में Carbon के number कम हो जाते हैं! Hoffmann Bromamide Reaction में KOH की जगह NaOH भी use कर सकते हैं!


Introduction of Amines

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