The term aroma generally denotes odour which helps in distinguishing different compounds. However, in chemistry, it is a branch of organic chemistry that studies compounds having particular structural, electronic, or chemical properties – typically characterized by a cyclic structure called an aromatic ring.

1. Aromatic Chemistry – An Introduction
Anil Kumar
Works for one of the quality Vinnerlabs cosmetics
active ingredients suppliers. Writes on cosmetics
active ingredients for personal care, home care, hair
colour, sun care products, pigmentation dryer and
dietary supplements including Iscotrizinol from
Vinnerlabs, also called as Uvasorb Heb /
Bemotrizinol sunscreen from Vinnerlabs.

2. The term aroma generally denotes odour which helps in distinguishing
different compounds. However, in chemistry, it is a branch of organic
chemistry that studies compounds having particular structural,
electronic, or chemical properties – typically characterized by a cyclic
structure called an aromatic ring.
What are aromatics?
Aromatics are hydrocarbons consisting of one or more conjugated
planar ring systems. These are accompanied by delocalized pi-electron
clouds instead of individual alternating single and double bonds. These
organic unsaturated compounds are also known as aromatics or arenes
and are stable.
The exceptional stability of these compounds is termed aromaticity, a
property in organic chemistry. A particular bonding arrangement causes
certain pi-electrons within a molecule by firmly holding it which results
in aromaticity.

3. Aromatic compounds and their importance:
Aromatic compounds play an indispensable role in improving life quality.
These compounds have a huge contribution to the development of
mankind and still have high potential. The major aromatics are benzene,
ortho-xylenes, and toluene. Phenol, styrene, aniline, acetophenone,
benzoic acid, benzaldehyde, and benzonitrile are some more aromatic
hydrocarbons. Aromatic compounds play crucial roles in biochemistry
and are used as starting materials for a wide range of products.

4. Aromacity properties are exhibited by aromatic compounds. Further, the
aromatic products are categorized into two broad categories based on
the presence or absence of benzene rings as benzenoids and non-
benzenoids respectively. When compared with similar non-aromatic
molecules, the aromatic molecules display enhanced chemical stability.
The molecules that can be aromatic will tend to change towards
aromaticity. The added stability changes the molecule’s chemistry.
Further, the aromatic compounds undergo nucleophilic and electrophilic
aromatic substitution reactions. The aromatic molecules can interact
with each other in so-called π–π stacking and also in an ‘edge-to-face’
orientation.

5. Aromatic compounds and their properties:
Arenes are non-miscible and nonpolar in water. These compounds are
unreactive and are usually used as solvents for several other nonpolar
compounds. The carbons to hydrogen ratio in arenes are high due to
which they get characterized by a sooty yellow flame.
Classification:
Arenes are classified into two categories and the classification is based
on the position of the functional group – nuclear-substituted
compounds and sidechain-substituted compounds.

6. Compounds need to fulfill certain conditions to be aromatic
compounds:
• The molecule must be cyclic.
• The atoms in the cyclic ring must be conjugated.
• Hydrocarbons can be classified as aromatic compounds if they follow
the Huckel rule. According to this rule, the planar ring must have (4n+2)
π electrons, in which n is any whole number. Based on this, the ring
systems having 2(n=0), 6(n=1), 10(n=2), 14(n=3), etc. pi electrons are
aromatic.
• Molecules should be planar or flat.

7. Aromatic Chemistry and its history:
Benzene and toluene are many of the earliest-known examples of
aromatic compounds. These compounds have distinctive smells. Such
property guided to the term ‘aromatic’ under which these types of
compounds get classified. With the eventual discovery of electronic
property, the term aromaticity got invented.
Chemists in the 19th century found that benzene was unreactive
towards addition reactions. This puzzled the chemists considering the
presumed high degree of unsaturation. August Kekule, a German
organic chemist, first proposed the cyclohexatriene structure for
benzene in 1865. A maximum number of chemists accepted the
structure as it reckoned for most of the familiar isomeric relations of
aromatic chemistry. Also, Huckel was the first to model the quantum
mechanical origins of aromaticity in 1931.

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