Functional Groups
Chemistry explains how carbon forms a large number of compounds with different structures and properties. One of the most important topics in Class 10 Science chapter – Carbon and Its Compounds is Functional Groups.
Functional groups are atoms or groups of atoms present in organic compounds that determine their chemical properties and reactions. Even if two compounds have similar carbon chains, the presence of different functional groups changes their behavior completely.
What are Functional Groups?
Functional Group are atoms or groups of atoms that replace one or more hydrogen atoms in hydrocarbons and determine the chemical properties of the compound.
In simple words: “Functional groups are reactive parts of organic compounds that decide their chemical behavior.”
For example:
- Alcohol contains –OH group
- Carboxylic acid contains –COOH group
Common Functional Groups Class 10
1.0Detailed Breakdown of Each Functional Group
1. Haloalkanes (Halogen Group)
When a hydrogen atom in an alkane is replaced by a halogen atom ($\text{Cl, Br, I}$), it forms a haloalkane. It uses a prefix system.
- General Appearance: R-X (where R is the carbon chain, X is Cl or Br)
Examples:
- Chloromethane: CH₃Cl
- Chloroethane: CH₃CH₂Cl
- Bromopropane: CH₃CH₂CH₂Br
2. Alcohols (-OH)
Alcohols contain a hydroxyl (-OH) group attached to a carbon atom. To name them, remove the ending '-e' from the parent alkane name and add the suffix '-ol'.
- General Formula: CₙH₂ₙ₊₁OH
Examples:
- Methane -> Methanol (CH₃OH)
- Ethane -> Ethanol (CH₃CH₂OH) — Commonly known as ethyl alcohol.
- Propane -> Propanol (CH₃CH₂CH₂OH)
3. Aldehydes (-CHO)
In aldehydes, a carbon atom is double-bonded to an oxygen atom and single-bonded to a hydrogen atom at the end of the carbon chain. To name them, replace the ending '-e' of the alkane with '-al'.
- Structure: The -CHO group is always located at carbon position 1.
Examples:
- Methanal (HCHO) — Commonly called Formaldehyde.
- Ethanal (CH₃CHO) — Commonly called Acetaldehyde.
- Propanal (CH₃CH₂CHO)
4. Ketones (-CO-)
Ketones contain a carbonyl group ($\text{C}=\text{O}$) located internally within the carbon chain. It can never be at the ends of the chain. Replace the ending '-e' of the alkane with '-one' (pronounced as own).
- Important Note: The simplest possible ketone must have at least 3 carbon atoms.
Examples:
- Propanone (CH₃COCH₃) — Commonly called Acetone, used as nail polish remover.
- Butanone (CH₃COCH₂CH₃)
5. Carboxylic Acids (-COOH)
Carboxylic acids contain a carboxyl group which consists of a carbonyl group C=O attached directly to a hydroxyl group (-OH) at the end of the chain. Replace the ending '-e' of the alkane with '-oic acid'.
Examples:
- Methanoic acid (HCOOH) — Commonly called Formic acid, found in ant stings.
- Ethanoic acid (CH₃COOH) — Commonly called Acetic acid; a 5-8% solution in water forms Vinegar.
2.0Homologous Series
A homologous series is a group or family of organic compounds that share the same functional group and exhibit similar chemical properties.
Key Characteristics:
- Successive members of a homologous series differ from each other by a -CH₂- unit.
- Successive members differ in molecular mass by 14 u (Mass of Carbon = 12u + Mass of 2 Hydrogens = 2u).
- They display a regular gradation in physical properties (e.g., melting and boiling points increase as the molecular mass grows).