Properties of Aromatic Hydrocarbons

Introduction:

The chemistry of class 11th introduces the students to all the elements and compounds in the periodic table. The students get an introductory platform for the upcoming topics and essential chemical reactions. The aromatic compounds have a special place and impact over the class 11th and even the higher studies. The Unacademy explains the subject with graphical representation and suitable formulas. The associate theorems and derivations have an easy explanation in a theoretical manner and their use in numerical problems. So, following the Unacademy notes will help the student clarify the topic and its use with the elements and chemical reactions.

Definition:

The aromatic compounds are chemical compounds that satisfy Huckel’s rule. This rule states that the elements in the complete conjugation (fully planar) of monocyclic polyenes are ready to possess aromatic stability. The aromatic compounds consist of planar molecules with conjugation in the ring format. These compounds have a name such as aromatics or arenes.

These compounds do not have a single or double molecular bond. Instead, they have the company of pi-electron clouds in the delocalization state. Aromatic hydrocarbons are the primary example of aromatic compounds bonding with the pi-electrons cloud. In aromatic hydrocarbons, many elements like Benzene; Toluene forms the sigma bond with planar ring conjugation.

Huckel’s rule:

All the aromatic compounds need to follow Huckel’s rule with complete assistance. Huckel’s rule states that a compound must tend to conjugate with its monocyclic polyenes on the planar ground to attain aromatic stability. Representing it mathematically, the polyenes must have the 4n + 2π electrons where the n is the integer whose value can be 0, 1,2,3,4, etc. 

According to this rule, a compound must have the π number of electrons with planar properties on both sides, i.e., below and above the plane of the molecule. This state of the molecule contains the sp2 carbon atoms undergoing the hybridization process, and all this must be the condition of Huckel’s rule. The entire electron must be in the ring format while obeying the rule.

Properties of aromatic compounds:

Various such properties are distinct from other compounds in the chemical reactions. Here are some of them:

⮚ These compounds have non-polar formations, and their consistency in water is non-miscible.

⮚ These compounds are highly unreactive.

⮚ These compounds have sooty yellow flame when are the prime characteristics of the arenes.

⮚ In aromatic compounds, the carbon to hydrogen ratio is very high and reactive.

⮚ The compounds are highly usable as solvents for different non-polar compounds.

Hydrogenation:

This is the process where the molecules of hydrogen undergo the formation of the compound in the presence of a chemical reaction. The chemical reaction may be the simple addition of the hydrogen molecule with the single or double bonds in a molecular structure. These bonds can be triple when the hydrogen molecules add to them. The addition of the hydrogen results in the dissociation process of the bonds, which has the term of hydrogenation reactions.  

Almost all the chemical compounds have multiple bonds where two atoms perform the chemical reaction in the presence of a catalyst. The hydrogenation reaction has vast importance in the industrial sector. Coal, petroleum, edible oils are sectors when the hydrogenation reactions are essential for the product formations.

Aromatic hydrocarbons:

Aromatic hydrocarbons are the prime result of aromatic compounds.  Many studies have many similar facts of aromatic hydrocarbons and compounds. The aromatic hydrocarbons are the products that have the circular structure of the organic compound and contain the sigma bond.

These hydrocarbons have the pi-electrons in delocalization form along with the sigma bond. These hydrocarbons do not saturate in their pure forms, which answers the query of what are aromatic hydrocarbons. They have more than one six-carbon ring, which associates with the planar surface. These are benzene rings with stable resonance and structure where the pi-electrons are under delocalization. Benzene, Xylene are some common examples of aromatic hydrocarbons. These hydrocarbons have higher demands in many of the industrial procedures and reactions. The petrochemical, plastics, and pharmaceutical industries are common examples of the use of aromatic hydrocarbons.

Reactions of aromatic hydrocarbons:

The aromatic hydrocarbons are a type of aromatic compounds that undergo several types of chemical reactions. Here are the mentions:

❖ Aromatic substitution reaction:

These are the reactions where the replacement of the hydrogen atom takes place. In this procedure, the substitute in the ring undergoes the replacement by the different substitutes of the other ring. This is the hydrogen atom that is replaceable during the chemical reaction and follows various properties of aromatic hydrocarbons. It has three categories: 

⮚ Nucleophilic reaction

⮚ Electrophilic reaction

⮚ Radical Nucleophilic reaction

❖ Coupling reaction:

In such reactions, two radical nature fragments form as a couple under the reaction with the metal catalyst. During the coupling reaction, certain bond formation takes place, which are:

⮚ Carbon-carbon bond forms during the reaction with vinyl arenes, alkyl arenes, etc.

⮚ carbon-oxygen bond- These bonds form Alkoxy compounds.

⮚ Carbon-nitrogen bond- These bonds form products such as Aniline.

Uses of aromatic hydrocarbons:

There are several uses of such aromatic compounds in many sectors. These uses have their presence in the biological as well as synthetic procedures. Some of the mentions are:

⮚ The amino acids and the nucleic acid in the human body contain aromatic hydrocarbons.

⮚ The chlorophyll present in plants in the form of green pigments in the form of aromatic hydrocarbons is a very common aromatic compounds.

⮚ These are usable in the formation of the dyes, drugs, and explosives with the compound aryl hydrocarbon.

⮚ The plastic and petrochemical industry has extensive uses of aromatic hydrocarbons for many processes.

⮚ Methylbenzene usable for the model glues is an aromatic hydrocarbon that takes part as the solvent in the making process.

Conclusion:

Here are the key points discussing the various chemical reactions and procedures of aromatic compounds. These Unacademy study notes on this topic cover all the aspects and relative properties. It motivates the students by engaging in language and factual description. Each part’s diagram and formula representation gives the students a clear view of procedures. The diagrams for each step explain the gaining and losing of atoms. Hence studying these notes provides clarity about the subject and explanation of the topic efficiently. Hence go through these notes and get a clear idea about the subject with expert opinions and factual information.