Representing Formulas of Organic Compounds
DP IB Chemistry Revision Notes 2023
Overview
- Organic compounds can be represented using various formulae:
- Empirical
- Molecular
- Structural
- Condensed Structural
- Skeletal
- Stereochemical
Types of Formulas
Empirical Formula
- Shows the simplest whole-number ratio of atoms in a molecule.
- Example: Hydrogen peroxide (H₂O₂) has an empirical formula of HO.
Molecular Formula
- Displays the actual number of atoms in a molecule.
- Example: Butane (C₄H₁₀) and Butene (C₄H₈).
Structural Formula
- Shows the spatial arrangement of all atoms and bonds, also known as the displayed or graphical formula.
- Example: 2-methylbutane shows all bonds between atoms.
Condensed Structural Formula
- Provides enough information for clarity while omitting most covalent bonds.
- Identical groups can be bracketed together; important bonds like double or triple bonds are always shown.
Skeletal Formula
- Simplified representation using straight lines for carbon-carbon bonds.
- Each line end or junction represents a carbon atom.
- Hydrogen atoms bonded to carbon are omitted unless part of a functional group.
- Example: Methane doesn't have a skeletal formula as it has only one carbon.
Stereochemical Formula
- Shows the three-dimensional arrangement around a chiral carbon.
- Solid line: in the plane
- Solid wedge: out of the plane
- Dashed wedge: behind the plane
Worked Examples
- Empirical and Molecular Formulas
- Examples provided for compounds like C₂H₄Cl₂ (Empirical: CH₂Cl) and C₆H₁₂O₂ (Empirical: C₃H₆O).
- Skeletal and Structural Formulas
- Example of drawing skeletal formulas for molecules like CH₃(CH₂)₃OH.
Key Concepts
- Chiral Carbon: A carbon atom bonded to four different atoms/groups, creating a tetrahedral shape.
- Functional Groups: Essential in identifying the properties and reactions of organic compounds.
Visualization
- Diagrams included for understanding structural, condensed, and skeletal representations.
- Stereochemical diagrams to differentiate spatial orientations.
Note: These notes are based on materials created by Save My Exams and are aligned with the DP Chemistry syllabus.