Chemical Properties of Amines Acylation Basicity

Basicity of Amines

Before diving into the chemical properties and basic nature of amines, let us first try to understand its definition. Amines are the types of organic compounds that are either mainly based on nitrogen or contain nitrogen. Generally, the structure of amines is similar to that of ammonia with three hydrogen atoms bonded to the nitrogen atom. However, they have different and extra properties due to the difference in carbon bondings or chains. Organic Alkane chain(alkyl) and aromatic ring (aryl groups) substitute one or more hydrogen atoms in the ammonia to form amines. There is one more compound similar to amine that contains three bond ammonia in the ground state called amides. Hence, it becomes crucial to be able to differentiate between these two structures and their properties. 

You can mainly differentiate by checking whether the molecule contains a nitrogen atom and carbonyl group or metal then that molecule is amide, not amine. Amines have basic properties. So you must be wondering why amines are basic in nature? Now let us get into the types, basic nature of amines, and chemical properties of amines.


Types of Amines

Amines can be classified into three categories, namely primary, secondary, and tertiary amines. It entirely depends upon the number of carbon atoms in the containing group in the amine chain structure. If there is only one group containing a carbon atom attached to the amine chain, then it is a primary amine molecule. Whereas if there are two groups containing carbon atoms attached to the amine structure, then it is a secondary amine. Similarly, if there are three carbon-containing groups, then it is a tertiary amine. According to energy, it is sometimes suitable to use the nitrogen-containing lone pair of electrons as a nucleophile. This lone allows a fourth group containing carbon to attach to the amine molecule. Such cases are referred to as quaternary ions of ammonium.  We can also classify compounds based on the number of amine groups they contain in their molecule(called amino groups). The organic compounds that have more than one amine groups can be named as Diamine, triamine, tetraamine and so on. Now let us try to understand the chemical properties of amines and why amines are basic in nature?  

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                             (Types of Amines where R is the carbon-containing group)  


Chemical Properties of Amines

There are several chemical properties of amines. The primary and secondary amines, including several amine derivatives, have a direct influence on their properties due to the presence of hydrogen bonding. The compounds containing phosphorus have a lower boiling point than that of amines and alcohol compounds have a higher boiling point than amines. The structure of alkanols is very much similar to that of amine except the presence of the hydroxyl group. In this case, the electronegativity of oxygen is higher than that of nitrogen, so alkanol compounds are more acidic in nature as compared to amines.. 

Due to the ability to form hydrogen bonds, the amines have tendencies of high solubility in water. The amine molecules such as Ethyl, triethyl, diethyl and Methyl are gaseous in nature. Whereas alkyl amines have liquid structure and higher weight amines have a solid structure. There is a fishy smell to liquid amines and ammonia smell to gaseous amines. The solubility of amines depends upon the number of carbon atoms in the molecule.


What is the Basicity of Amines?

So why amines are basic in nature? The basic nature of amines or basicity of amines is reasonably strong. Similar to ammonia, they can act as bases as well. The basicity of various amine molecules depends upon several factors. First, there should be the availability of the lone electron pair on the nitrogen atom. Second, the substitute groups and their electronic properties directly affect the basicity( such as decreasing basicity with aryl group and increasing basicity with alkyl groups). Lastly, the solving capabilities of amine that mainly depends upon the solved utilized in the reaction. The soluble ability of amines in water mostly depends upon hydrogen bonds in water and lone pairs in amines. Further, we will discuss the acylation of amines. .       


What is Acylation of Amines?

The method by which an acyl group is bonded to the compound is called acylation. In the case of primary, secondary, aromatic, and aliphatic amines, the nucleophilic substitution reaction takes place with acid chlorides, esters, and anhydrides. This process is referred to as acylation of amines. There are various end products of acylation. These reactions require the presence of a more substantial base than amine such as pyridine that helps remove the hydrogen chloride(formed during) in the reaction. Therefore, the right-hand side shift in the reaction is noticeable.  

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                                                       (Acylation of amine)

FAQ (Frequently Asked Questions)

1. What Are Aromatic Amines?

When the aromatic ring structure has a direct attachment to the nitrogen atom, then these structures are called aromatic amines. The aromatic ring decreases the basicity of amines by significant margins. This phenomenon occurs due to its electron-withdrawing properties. We can increase or reduce the basicity by changing the substitute group attached to the aromatic ring. The aromatic ring becomes more reactive to other molecules due to the presence of lone pairs of electrons on the nitrogen atom. The aromatic ring experiences an opposite effect due to lone pair electrons on the nitrogen atom.

2. What Are The Uses Of Amines?

There are several wonderful uses of amines in the industry. The manufacturing process of azo dyes utilizes primary aromatic amines as an initial material. Also, the formation of azo compounds takes place due to the coupling reaction of diazonium salt( formed after azo dyes react with nitrous acid). Several dying companies around the world utilize these azo compounds due to their highlight coloured appearance. For instance, some of these colours are sunset yellow, ponceau, direct brown, and orange.