Preparation of Amines and Reactions

Amines are considered to be very essential chemicals in various biological processes. However, many believe that they are relatively basic compounds from the context of organic chemistry. Amines are organic compounds and functional groups consisting of nitrogen atoms with a lone pair of electrons. They are best described as the derivatives of ammonia, as they contain one or more atoms of hydrogen. There are various types of amines; however, they are mostly classified based on the number of hydrogen atoms, which are replaced by an alkyl or aryl group. In the following article, various aspects of preparations and reactions of amines are discussed. 

PREPARATION OF AMINES AND REACTION

What are Amines? 

Amines are organic compounds and functional groups consisting of nitrogen atoms with a lone pair of electrons. They are best described as the derivatives of ammonia, as they contain one or more atoms of hydrogen. However, these hydrogen atoms can be replaced with alkyl or aryl groups. Here, the compounds with the nitrogen group attached to a carbonyl in the overall structure are termed amides. Their structure is R-CO-NR’R”. 

The amine groups tend to form a bond with an aromatic or conjugated cyclic structure and are known as aromatic amines. It should be noted that these aromatic structures tend to significantly decrease the overall alkalinity of the amines. On the other hand, the presence of an amine group tends to lead to a major decline in the reactivity of the ring. This happens mainly due to the electron-donating effect. 

Classification of Amines

There are various types of amines; however, they are mostly classified based on the number of hydrogen atoms, which are replaced by alkyl or aryl groups. This is done in the parent ammonia, as amines are a derivative of ammonia. Thus, it can be said that the classification of amines is done differently than that of the alkyl halides or the alcohols. This is because of the three neutral single bonds with a lone pair that are formed due to the three nitrogen atoms found in the amines. It should be noted that a maximum of three hydrogen atoms of ammonia can be replaced by other groups. Upon further treatment with a halide, the lone pair can be removed and one group can be added further. 

Amines are classified into four types:

• Primary Amines: These are formed as a result of the substitution of the lone hydrogen atom by an alkyl or aromatic group. Amino acids and methylamine are some examples of primary amines. 

• Secondary Amines: These have two organic substituents – alkyl or aryl, or even both. One hydrogen binds to nitrogen. Dimethylamine is a common example of secondary amine, while diphenylamine can be a form of aromatic amine.

• Tertiary Amines: When the nitrogen contains three organic substituents, it is known as tertiary amines. Trimethylamine and EDTA are some examples of tertiary amines.

• Quaternary Amines: These are those wherein the nitrogen contains four organic substituents and have a positive charge. These are also known as cyclic amines. Some examples of this form of amines are Piperidine and Aziridines.

Importance of Preparation of Amines and Reactions

Amines are essential chemicals in various biological processes. However, many believe that they are relatively basic compounds from the context of organic chemistry. Essentially, it can be said that amines tend to play a very important role in the survival of life. This is mainly due to the reason that the amines are associated with and involved in the creation of amino acids, which are considered to be building blocks of proteins in every living being. The importance of amines, their preparation, and reactions can be understood through the fact that many vitamins are also built from various types of amino acids. 

Amines can be prepared by reduction of Aromatic nitro compound.

Example- Nitrobenzene converted to aniline in presence of tin(Sn), concentrated HCl and NaOH.

C6H5NO2 + Concentrated (HCl +NaOH )(In presence of Sn)−−−−−−→C6H5NH2

Reactions of Amine

• Primary aromatic amine, aniline forms stable Diazonium salts at 0 degree temperature in presence of HCl and NaNO2.

NaNO2+C6H5NH2 +2HCl (Temperature0–5°C)−−−−−−→C6H7N2Cl +NaCl+2H2O

• Secondary Aromatic amines with nitrous acid in presence of HCl and NaNO2 form nitrosamine.

(CH3)2NH + HCl + NaNO2 (HONO/H2O)−−−−−−→ (CH3)2N−N=O

Dimethylamine N-Ntrosodimethylamine

• Aromatic amines with Hydrochloric acid to form Salt as amines are basic in nature.

NaNO2+Ar-NH2 +2HCl →Ar-N2Cl +NaCl+2H2O

• The reaction of benzenesulphonyl chloride yields N- ethylbenzenesulphonyl amide when reacted with primary amine.

C6H5SO2Cl + NH2-C2H5 → C6H5SO2-NH2C2H5

• Secondary amine and benzene sulphonyl chloride form N,N- Diethyl Benzene Sulphonamide.

C6H5SO2Cl + C2H5-NH-C2H5 → C6H5SO2-NH(C2H5)2

• Aniline in reaction with bromine water forms 2,4,6 tribromoaniline.

C6H5NH2+ Br2/H2O → C6H4Br3N

Examples of Preparation of Amines and Reactions 

The following list presents some examples and uses of amines, their preparation, and reactions:

• They are majorly used in the pharmaceutical industry. Demerol and Morphine are used in the form of analgesics, which are essentially painkillers. 

• Amines are used for activities such as pest control and leather tanning in daily lives. Man-made dyes are the primary area of application and use of amines.

• Amines are used to make azo-dyes and nylon, along with various types of medicines and drugs. 

• They are mainly used in developing different chemicals for protecting crops, medicines, and also for the purification of water. 

• Amines are also used in various products meant for personal use. 

• The most common type of amine used at the global level is ethanol amine. 

• Methamphetamines and amphetamines are recreational drugs that are very basic in nature. They have pH values above seven. Since their nature is basic, acids are used for neutralizing them. This neutralisation action and its reaction lead to the formation of alkylammonium salts, which are used in several types of industries and sectors. 

CONCLUSION

Amines are considered to be very essential chemicals in various biological processes. However, many believe that they are relatively basic compounds from the context of organic chemistry. The presence of an amine group tends to lead to a major decline in the reactivity of the ring. This happens mainly due to the electron-donating effect.