Structure Formula: Shows the arrangement of atoms in a compound, e.g., Methane (CH₄) has a tetrahedral shape with one carbon atom bonded to four hydrogen atoms.
Molecular Formula: Represents the total count of each type of atom in the compound, e.g., Methane is represented as CH₄.
Isomers
Definition: Compounds with the same molecular formula but different arrangement of atoms.
Example: Gloves analogy (same number of fingers but different arrangements).
Example: N-butane and 2-methylpropane (both have the formula C₄H₁₀ but different structures).
Difference Between Isomerism and Isomers
Isomerism: The ability of compounds to form different structures.
Isomers: Actual outcomes from isomerism, i.e., compounds with the same formula but different structures.
Important Point
Isomers exhibit different physical properties (e.g., alcohol vs. ether).
Types of Isomerism
1. Structural Isomerism
Categories:
Chain Isomerism
Position Isomerism
Functional Group Isomerism
Metamerism
Tautomerism
Ring Chain Isomerism
2. Stereo Isomerism
Categories:
Geometric Isomerism
Optical Isomerism
Structural Isomerism Explained
Chain Isomerism
Isomers with different numbers of carbons in the main chain.
Example: N-butane vs. Isobutane.
Position Isomerism
Isomers with the same functional group attached at different positions.
Example: Different locations of methyl groups in butane derivatives.
Functional Group Isomerism
Same molecular formula but different functional groups (e.g., aldehyde vs. ketone).
Metamerism
Isomers with the same functional group but different alkyl groups (e.g., diethyl ether vs. methyl propyl ether).
Tautomerism
Interconversion of compounds with the same molecular formula but differing in the position of functional groups, commonly seen in carbonyl compounds (e.g., ketone vs. enol).
Ring Chain Isomerism
Isomers distinct as cyclic (ring) or acyclic (open chain) structures but with the same formula.
Stereo Isomerism Explained
Geometric Isomerism (Cis-Trans Isomerism)
Isomers differing in the position of identical groups across a double bond.
Cis: Same side of the double bond.
Trans: Opposite sides of the double bond.
Example: cis-2-butene vs. trans-2-butene.
Optical Isomerism
Related to compounds that can rotate polarized light and have an asymmetric carbon.
Enantiomers: Mirror images that are non-superimposable.
Diastereomers: Stereoisomers that are not mirror images.
Optical Isomerism Examples
Lactic Acid: Isomers that can rotate polarized light in opposing directions.
Tartaric Acid: Has multiple stereoisomers, with some being symmetrical (meso form) and others being enantiomers.
Summary
Functional isomer examples: Aldehyde vs. ketone, carboxylic acid vs. ester, ethers vs. alcohols.
Various forms of isomerism through structural and stereochemical changes can lead to compounds having different chemical behaviors.