Jump to a key chapter
- This article is about the uses of amines in organic chemistry.
- We'll start with a recap of what amines actually are before exploring their uses.
- You'll be able to see examples of amines in industry and in real life.
- This will include looking at quaternary ammonium salts and azo compounds.
- We'll finish by summarising the importance of amines.
What are amines?
In Amines, we introduced you to a new type of organic molecule: amines. These are ammonia derivatives, characterised by a nitrogen atom bonded to at least one organic hydrocarbon R group. Amines can be further divided into three different types:
- Primary amines contain a nitrogen atom bonded to just one R group and have the general formula NH2R.
- Secondary amines contain a nitrogen atom bonded to two R groups and have the general formula NHR2.
- Tertiary amines contain a nitrogen atom bonded to three R groups and have the general formula NR3.
You can also get quaternary ammonium cations. These consist of a nitrogen atom bonded to four R groups. The nitrogen atom bonds to the fourth R group using a dative covalent bond. Quaternary ammonium ions are an important part of quaternary ammonium salts.
Characteristics of amines
Let's now briefly consider some of the characteristic properties of amines:
- Amines are polar molecules.
- Amines form hydrogen bonds, both with other amine molecules and with water. This means that they have high melting and boiling points, and that shorter-chain amines are soluble in aqueous solutions.
- Amines can act as both nucleophiles and bases. Nucleophiles are electron-pair donors whilst bases are hydrogen ion acceptors. This enables many of their reactions.
Check out Amines for a more detailed look into the properties of amines and the characteristics of these molecules. Head over to Amines Basicity if you want to learn more about their reactions as nucleophiles and bases.
Uses of amines in daily life
Now that we know not only what amines are, but also about their characteristics and properties, we can look at some of their applications in daily life. After that, we'll consider their uses in industry.
- Amines are found in every cell in your body in the form of proteins. Proteins are condensation polymers, made up of repeating units called amino acids. Each amino acid has a carboxyl and an amine functional group. Multiple amino acids join together to form a long polymer chain. This chain then folds into a specific 3D shape that is unique to each protein.
- Another type of polymer involving amines is polyamides. These include nylon, Kevlar, and a variety of plastics.
- Many common drugs and pharmaceuticals are amines. These include the analgesic morphine, the decongestant ephedrine, and the antidepressant amoxapine.
- Amines play a role in cosmetics, such as shampoos, soaps, and shaving creams. We'll look at how they are made in just a second.
- The common compound tetramethylammonium chloride, used to disinfect water, is also an amine.
- Amines are the precursor to many dyes and tanning agents.
Head over to Proteins Biochemistry to learn more about proteins. You can also learn more about polyamides and other polymers in Condensation Polymers.
Uses of amines in industry
Knowing what we use amines for is well and good, but how do we make those products in industry? It is now time to learn about two important industrial applications of amines.
- Quaternary ammonium salts.
- Azo compounds.
Quaternary ammonium salts
The first important use of amines in industry is making quaternary ammonium salts.
Earlier, we learned that a quaternary ammonium ion consists of a nitrogen atom bonded to four organic hydrocarbon R groups. It has a permanent positive charge, which means that it can bond ionically to negatively-charged ions, forming a quaternary ammonium salt.
Uses of quaternary ammonium salts
Quaternary ammonium salts have a few uses: conditioners, detergents, and antimicrobial agents. They're suitable because of one particular characteristic: their charge. In conditioners and fabric softeners, the positive charge of the ammonium ion is attracted to the negative charge of wet clothes or hair, and the ammonium ions form a layer on the surface. This helps keep the hair or fabric smooth and glossy. In detergents and antimicrobial agents, the positive charge of the ammonium ion is attracted to the negative charge of bacterial cell walls. This disrupts the wall and damages the cell.
Azo compounds
The second use of amines in industry is making diazonium salts and azo compounds. Diazonium salts contain an -N+≡N group, while azo compounds contain an N=N azo group. Producing azo compounds involves a multi-step synthesis:
- Phenylamine (C6H5NH2) is reacted with nitric(III) acid (HNO2) at low temperatures to form a diazonium salt.
- The diazonium salt reacts with another aromatic organic molecule to form an azo compound.
Let's investigate those steps in more detail.
Forming a diazonium salt
Firstly, phenylamine reacts with nitric(III) acid at low temperatures to form a diazonium salt containing the -N≡N+ group. Nitric(III) acid is extremely reactive and so must be prepared in situ. To carry out the reaction, we mix phenylamine with a chilled solution of a strong acid, such as hydrochloric acid (HCl), and then add sodium nitrite (NaNO2). The hydrochloric acid and sodium nitrite first react to form nitric(III) acid and sodium chloride:
$$HCl+NaNO_2\rightarrow HNO_2+NaCl$$
The nitric(III) acid formed then reacts with phenylamine and more hydrochloric acid to form a diazonium salt:
$$C_6H_5NH_2+NHO_2+HCl\xrightarrow{\text{< 10}^\circ \text{C}} C_6H_5N^+N\space Cl^-+2H_2O$$
Here's a diagram to help you understand the structure of the molecules involved.
This reaction must be carried out below 10°C. If you heat the mixture, a different reaction takes place. Instead, you produce phenol (C6H5OH), nitrogen gas, and water:
$$C_6H_5NH_2+NHO_2+HCl\xrightarrow{\text{< 10}^\circ \text{C}} C_6H_5OH+N_2+H_2O$$
Forming an azo compound
The second step of the process involves reacting the diazonium salt with another aromatic organic molecule. This is an example of a coupling reaction, forming an azo compound with the N=N azo functional group. In this reaction, the diazonium ion acts as an electrophile and substitutes into the second molecule's benzene ring.
One example is the reaction of a diazonium salt with phenol. This reaction takes place in a basic solution, typically of sodium hydroxide, and produces an azo compound with two benzene rings, one with an -OH group. These benzene rings are joined by an N=N azo bridge. It also produces an acid, which varies depending on the diazonium salt used.
Here's the equation for the reaction between a diazonium chloride salt and phenol. The structural formulae of these molecules can get a little tricky, so we've used displayed formulae to show you the reaction.
A similar reaction takes place between diazonium salts and phenylamine. This produces another type of azo compound, but this time the second benzene ring has an -NH2 amine group instead of a phenyl group:
Uses of azo compounds
To conclude this section, we'll consider the uses of azo compounds. Thanks to their two benzene rings, which are full of delocalised pi electrons, azo compounds are very stable and present with vivid colours. Azo compounds, therefore, form the basis of many dyes, including ones such as methyl orange that are used as pH indicators. They're also used in the textile industry and in tattoo inks.
Importance of amines
This article is dedicated to the uses of amines, both in everyday life and in industry, and so you should now have an appreciation of why these molecules are so valuable. However, we'll end by summarising a few of reasons why amines are important to us. Then, we'll take a deep dive into the importance of amines in the human body.
- Amines form the basis of many dyes, cosmetics, and toiletries.
- Approximately 42% of all drugs rely on amines - without them, our first-aid kits would be severely depleted!
- Amines also help us clean up our waste gases. These molecules are used to 'sweeten' polluted gases released by oil refineries and processing plants by removing hydrogen sulfide (H2S) and carbon dioxide (CO2). As a result, they help mitigate climate change.
- Furthermore, amines are vital inside the human body, as you'll discover below.
Importance of amines in the human body
Without amines, we probably wouldn't exist. It sounds dramatic, but it is true! This is because all amino acids are amines. Let's explore their uses and importance inside the human body.
- Amino acids are the building blocks of proteins. Amino acids are small monomers, but when they join into long chains, they can fold up into millions of unique, intricate protein polymers, with different shapes, functions and purposes.
- Proteins are used to build and repair muscles.
- Enzymes are also types of proteins. Enzymes are biological catalysts, meaning that they increase the rate of reactions inside the body. Without them, many essential processes (like respiration and DNA synthesis) would be so slow that they couldn't support life.
- Ever heard of serotonin? This 'happiness hormone' is a type of neurotransmitter that works in the brain, and one of its many roles is regulating your mood. You guessed it - serotonin is also an amine. Many other neurotransmitters, such as histamine and dopamine, are amines too.
- The hormones adrenaline, thyroxine, and melatonin, all contain the amine functional group. Adrenaline controls your 'fight or flight' response, whilst thyroxine is involved in metabolism, and melatonin helps regulate your circadian rhythm.
We explore the biochemistry of amino acids in the article Amino Acids. You can also look at proteins from a chemist's point of view in Proteins Biochemistry. However, you can also head over to the biology side of StudySmarter to find out about amino acids, proteins, neurotransmitters, and hormones, from a more biological stance. These articles might help you and give you more to think about:
- Proteins.
- Responding to Change.
- Homeostasis.
Uses of Amines - Key takeaways
- Amines are ammonia derivatives that contain a nitrogen atom bonded to one or more organic hydrocarbon R groups.
- Amines have the following characteristics:
- They are polar.
- They can form hydrogen bonds.
- In addition, they can act as both bases and nucleophiles.
- Amines are found in everyday items such as proteins, plastics, pharmaceuticals, cosmetics, and dyes.
- In industry, amines are turned into quaternary ammonium salts and azo compounds.
- Quaternary ammonium salts contain a nitrogen atom bonded to four R groups and are used in detergents, conditioners, and antimicrobial agents.
- Azo compounds are made from diazonium salts. These in turn are made from phenylamine and nitric(III) acid. Azo compounds are used as dyes.
- Amines are also important inside the human body.
Learn with 7 Uses of Amines flashcards in the free StudySmarter app
We have 14,000 flashcards about Dynamic Landscapes.
Already have an account? Log in
Frequently Asked Questions about Uses of Amines
What are some examples of amines?
Examples of amines include methylamine and phenylamine. However, we also find amines in daily life. For example, all proteins are made from amines known as amino acids, whilst many drugs such as morphine are also amines.
What are amines used for?
Amines are used in cosmetics, dyes, pharmaceuticals, and plastics.
What is the importance of amines?
Amines play important roles in many drugs, cosmetics, detergents, plastics, and antimicrobials. They also make up all proteins, which are found in every cell in our body.
Are amines acidic?
Amines aren't acidic, but basic. This means that they act as proton acceptors.
What are the physical properties of amines?
Amines can form hydrogen bonds. This means that they have high melting and boiling points.
Shorter-chain amines are soluble in water.
About StudySmarter
StudySmarter is a globally recognized educational technology company, offering a holistic learning platform designed for students of all ages and educational levels. Our platform provides learning support for a wide range of subjects, including STEM, Social Sciences, and Languages and also helps students to successfully master various tests and exams worldwide, such as GCSE, A Level, SAT, ACT, Abitur, and more. We offer an extensive library of learning materials, including interactive flashcards, comprehensive textbook solutions, and detailed explanations. The cutting-edge technology and tools we provide help students create their own learning materials. StudySmarter’s content is not only expert-verified but also regularly updated to ensure accuracy and relevance.
Learn more