What is an homologous series? Explain with an example.

Organic compounds are the backbone of chemistry involving carbon. These compounds contain carbon atoms bonded to hydrogen, oxygen, nitrogen, or other elements. Organic compounds are found everywhere, from the food we eat to the clothes we wear. Some common examples include carbohydrates, proteins, and hydrocarbons.
Organic chemistry is essentially the study of these compounds. The versatility of carbon's bonding allows for complex structures, leading to a variety of compounds.
Organic molecules can form chains, branched structures, or rings, giving rise to vast diversity.

• Carbohydrates are compounds with carbon, hydrogen, and oxygen.
• Proteins are built from amino acids containing carbon, hydrogen, oxygen, and nitrogen.
• Hydrocarbons comprise only carbon and hydrogen.

Hence, the classification of these compounds is crucial for understanding various chemical reactions and properties.

The general formula of an organic compound series helps predict the molecular structure. A general formula is a mathematical representation of the composition of compounds in a homologous series. It outlines the relationship between the number of carbon atoms (Cₙ) and hydrogen atoms (Hₓ).

For example, the general formula for alkanes is CₙH₂ₙ₊₂. Here, 'n' represents the number of carbon atoms, and '2n+2' represents the number of hydrogen atoms.
Understanding the general formula is essential because:

• It helps determine the molecular formula of any member in the series.
• It provides insight into the structure and stability of the compounds.
• It explains the patterns in properties observed within the series.

Another example is the alkene series, which follows the general formula CₙH₂ₙ, indicating each molecule has two hydrogen atoms for each carbon atom.

Physical and chemical properties are crucial for distinguishing and understanding organic compounds.
Physical properties include:

• Melting and boiling points: These generally increase with the molecular size in a homologous series.
• Density: Larger molecules often have higher densities.
• Solubility: This can vary; smaller molecules often dissolve in water, while larger ones may not.

Chemical properties refer to how a compound reacts with other substances.
For example:

• Alkanes are relatively unreactive compared to alkenes and alkynes.
• Alkenes and alkynes react readily with halogens, hydrogen, and other chemicals due to their double and triple bonds.
• Functional groups, like alcohols (-OH), carboxylic acids (-COOH), and amines (-NH₂), influence reactivity significantly.

By studying these properties, chemists can predict how a compound will behave in various environments, impacting fields from pharmaceuticals to materials science.