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Amine Definition

Under organic chemistry, Amine meaning recognized as a derivative of ammonia. It is a chemical compound categorized under organic nitrogen compounds which contain nitrogen atoms with a lone pair of electrons. Basically, in amines hydrogen atoms are replaced by an alkyl or aryl group. With this basic animation meaning, let us study various types of amines, properties and naming systems.


Types of Amines

Amines are categorized based on nature into aliphatic amines and aromatic amines. Besides amines, aryl and alkyl are also divided into three subcategories which depend on the count of carbon atoms linked to nitrogen and the number of hydrogen atoms are substituted. They are as follows-


1) Primary Amines ( 10 Amines)

Primary amines created when an alkyl or aromatic group substitutes one of three hydrogen atoms in ammonia. Examples of primary alkyl amines include methylamine, amino acids, whereas primary aromatic amines include aniline.

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2) Secondary Amines (20 Amines)

Secondary amines contain two organic substituents either alkyl or aryl or both which are bound to the nitrogen together with one hydrogen. Examples include dimethylamine and aromatic Amine like diphenylamine.

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3) Tertiary Amine (30 Amines)

Tertiary amines are recognized where the nitrogen consists of three organic substituents. Examples of tertiary Amine are trimethylamine and EDTA.

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4) Quaternary Amines ( 40 Amines)

Quaternary amines bear a positive charge and are those where the nitrogen contains four organic substituents and 

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Interestingly, the fourth subcategory of amines known as cyclic amines also exists—cyclic amines based on the connectivity of the substituents connected to the nitrogen. However, cyclic amines are either secondary or tertiary Amine. Examples are the six-membered ring piperidine or the 3-membered ring aziridine.


Nomenclature of Amines

The conventional and popular system for naming amines is to the recognition of each group that connected to the nitrogen atom and then suffixed it with -Amine. As in methylamine, CH₃NH₂; N-ethyl-N-propylamine (or ethyl(propyl)amine), CH₃CH₂NHCH₂CH₂CH₃; and tributylamine, (CH₃CH₂CH₂CH₂)₃N. 

Any or more of the listed groups are in alphabetical order; Ns or inner brackets aids to show what groups are bound to nitrogen rather than to each other.

Several aromatic amines and most cyclic amines have names (e.g., aniline) that might be utilized as a parent to assign the other associated, as in N, N-dimethylaniline.

Another method substitutes a hydrocarbon name’s terminal -e with the suffix-amine for the functional group −NH₂. The largest group preferred as the parent of secondary and tertiary amines, and the other groups were chosen as substituents.


Examples 

1. CH₃− CH₂ − CH (NH₂) – CH₃ (2- Butylamine)

2. CH₃− CH₂ − CH (NHCH₃) – CH₃ (N – Methyl -2- Butylamine)

3. H₂N − CH₂– CH₂– OH (Ethanolamine)


Properties of Amine

  • The lower aliphatic amines are gaseous with a fishy odour.

  • Primary amines are liquids at room temperature comprising three to four carbon atoms, whereas higher amines are solids.

  • Aniline and other arylamines are generally colourless. However, when stored in the open, they get painted due to atmospheric oxidation.

  • Lower aliphatic amines are soluble in water as they make the bond with the hydrogen atom of water. However, if the size of the hydrophobic alkyl portion increases, Amine molar weight decreases and solubility also decreases.

  • Lower amines in the soil are insoluble. Organic solvents such as ethanol, benzene, and ether used to dissolve amines readily.

  • Primary and secondary amines are often involved in the intermolecular interaction due to the interaction of hydrogen and nitrogen interacting with the hydrogen of other atoms.

  • Intermolecular forces are more observed in primary amines compared to secondary due to the presence of two hydrogen atoms. In contrast, tertiary amines do not have intermolecular forces due to the absence of free hydrogen atoms.

  • Aromatic amines are comparatively less basic than aliphatic amines because lone pairs of electrons on a nitrogen atom are delocalized and less available for acid.

 

 Fun Facts

  • Do you know about Amines generated by protein fragmentation or fermentation? Protein constituting elements, i.e. amino acids, breaks down into amines. Amines are present in cheese, chocolates, beer, yeast extracts and fish products. They are also available in certain fruits and vegetables, e.g. bananas, avocados, tomatoes, and broad beans.

  • Do you know amines play an essential role in the survival of human beings? They are responsible for creating amino acids in living beings. Not just proteins, many vitamins are built on amino acids. Serotonin is a crucial amine that operates as neurotransmitters for the brain. It regulates the feelings of hunger, sleep regulation, and emotions; overall brain functions in general. 

FAQ (Frequently Asked Questions)

1. Explain the Effect of Substituents on the Basicity of Amines.

Nitrogen atoms having a lone pair of electrons is the prime reason for the basic nature of Amine. According to the Lewis acid-base concept, this lone pair of electrons donate making amines a Lewis base.                                           

Also, according to the Bronsted- Lowry definition, Bronsted Lowry bases accept a proton. Amines contain a nitrogen atom bound to some grouping of carbon and hydrogen atoms and can make three bonds total. Amines react with acids and gain a hydrogen ion. This reaction gives Amine a positive charge. 

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The amine can accept hydrogen atoms to act as Bronsted Lowry Base.

2. List Down the Application the Amines

Below is the application of amines.

  • Amines found in products of personal care. Ethanolamines are the universal type of Amine used in the global market.

  • Analgesics like Morphine and Demerol used as painkillers comprises amines.

  • Methamphetamines and amphetamines known for recreational drugs are basic with pH greater than seven and hence neutralizes the action of acids.

  • Amines used in making azo-dyes and nylon apart from medicines and drugs. It also helps in water purification, in pest control, and leather tanning.