There are over 27 million chemical compounds known and majorly organic compounds. There are many industries such as the food industry, pharmaceutical industries, and the color dye industry in which organic compounds are used. As a result, organic compounds have become our basic need in today's daily life.

Studying these many organic compounds separately is next to impossible. Thus there is a need for the classification of organic compounds. Organic substances can be categorized in two ways structurally and chemically i.e.,

• Based on structure
• Based on functional group

Table of content:

• Classification
• Acyclic Compounds
• Cyclic Compounds
• Practice Problems
• Frequently asked questions

Classification:

A general classification of the organic compounds on the basis of structure is given below:

Acyclic compounds:

These are the compounds formed by joining carbon atoms to form an open chain. Aliphatic compounds are another name for these compounds.

Their structure might be either straight or branched chains.

Example of straight-chain Acyclic compound:

n-Butane:

n-Ethane:

Example of branched-chain Acyclic compound:

Isobutane:

Isopentane:

Neopentane:

Cyclic compounds:

These are the compounds in which the carbon atoms are linked to each other or to the atoms of other elements in such a manner that the molecule has a closed-chain or cyclic or ring structure.

Examples:

Structure	Name
	Cyclohexane
	Benzene
	Pyridine

1. Alicyclic (or aliphatic cyclic compounds): An alicyclic compound contains one or more all-carbon rings which may be either saturated or unsaturated, but do not have aromatic character.

Example: Cyclopropane

Alicyclic compounds are further classified into homocyclic and heterocyclic compounds:

• Homocyclic Compounds: In homocyclic compounds, all the atoms that form the ring are only carbon atoms.

Example: Cyclohexane

• Aliphatic heterocyclic Compounds: In aliphatic heterocyclic compounds, the cyclic molecule involves carbon as well as heteroatoms like N, O, S, etc.

Example: Tetrahydrothiophene

1. Aromatic Compounds:Chemical compounds known as aromatic compounds are those that lack individual alternating double and single bonds in favor of conjugated planar ring systems and delocalized pi-electron clouds. They are also known as arenes or aromatics. Toluene and benzene make for the best examples. Aromatics require satisfying Huckel’s rule (4n + 2)π electrons.

Example: Benzene

Aromatic compounds are further classified into benzenoid, non-benzenoid, and heterocyclic aromatic compounds.

• Benzenoid Compounds: It involves only benzene rings.

Example: Naphthalene, toluene, etc.

• Non-benzenoid Compounds: A compound that exhibits an aromatic behavior but does not contain any benzene ring. The non-benzenoid aromatic compounds have one or more rings fused together but none of the rings is a benzene ring.

Example: Azulene

• Aromatic Heterocyclic Compounds: In aromatic heterocyclic compounds, the ring contains atoms of carbon as well as any other heteroatoms like N, S, O, etc., but these are still aromatic. These are not just heterocyclic molecules, these are aromatic heterocyclic molecules.

Example: Pyrrole

Practice Problems:

Q1: Cyclopentane is an example of which type of organic molecule?

A) Homocyclic

B) Non-benzenoid

C) Aromatic Heterocyclic

D) Acyclic

Answer : (A)

Solution:

An alicyclic compound is an organic compound that is both aliphatic and cyclic.

Cyclopentane is a five-membered ring constituting only carbon atoms hence it is homocyclic.

Q2: Pyridine is an example of which type of organic molecule?

1. Homocyclic
2. Non-benzenoid
3. Aromatic Heterocyclic
4. Acyclic

Answer : (C)

Solution:

Pyridine is an example of a six-membered aromatic heterocycle and has an electronic structure similar to benzene.

Q3: Which among the following is not an example of an Acyclic compound?

(A) Acetaldehyde

(B) Ethane

(C) Cyclopropane

(D) Isobutane

Answer: (C)

Solution:Cyclopropane is a three membered cyclic compound containing all carbon atoms.

Q4: Which among these is not associated with aliphatic compounds?

1. They contain (4n+2)π electrons
2. Contain straight-chain compounds
3. Contain branched-chain compounds
4. Has an appropriate number of H-atoms and functional groups

Answer: (A)

Solution:Aliphatic compounds generally do not contain aromatic character, hence they do not follow the huckel rule.

Q5: Which among the following is not an example of a Cyclic compound?

1. Benzene
2. Furan
3. Cyclopropane
4. Isobutane

Answer: (D)

Solution:Benzene, furan and cyclopropane all are cyclic organic compounds, isobutane is a branched acyclic organic compound.

Frequently asked questions-FAQs:

Q 1: Write some applications of organic compounds.

Answer: There are many industries such as the food industry, pharmaceutical industries, and the color dye industry in which organic compounds are used. As a result, organic compounds have become our basic need in today's daily life.

Q 2: Give some examples of organic compounds used in medicine.

Answer: Organic compounds, frequently split into big groups of tiny organic molecules (e.g., atorvastatin, fluticasone, clopidogrel) and "biologics" (infliximab, erythropoietin, insulin glargine), the latter more generally employed as protein pharmaceutical goods, are most commonly utilized as medicinal products.

Q 3: Explain some properties of Organic compounds.

Answer: Physical properties of organic compounds of interest usually provide quantitative and qualitative information. The melting point, boiling point, and refraction index are all examples of quantitative data. Odor, durability, solubility, and colour are examples of qualitative qualities.

Q 4: What is the major source of organic compounds?

Answer:The main source of organic compounds is fossil fuels (petroleum, coal, plants, animals etc). hey have a very strong odor. For example, Benzene, Aniline, Naphthalene and so on.