Introduction to Organic Chemistry

Organic chemistry: Study of carbon-containing compounds and their properties
Focus on hydrocarbons: Compounds composed of Carbon (C) and Hydrogen (H)

Types of Hydrocarbons

Alkanes (Saturated hydrocarbons)

Contain only single ($\sigma$) bonds
Example: $\ce{C_{2}H_{6}}$

Alkenes (Unsaturated hydrocarbons)

Contain at least one carbon-carbon double bond ($\sigma$ & $\pi$)
Example: $C₂H₄/$

Alkynes (Unsaturated hydrocarbons)

Contain at least one carbon-carbon triple bond ($\sigma$ & $2\pi$)
Example: C₂H₂

Aromatics

Contain a benzene ring
Example: C₆H₆

Molecular Representations

Isopentane (Example of an Alkane)

Carbon atoms in alkanes adopt a tetrahedral geometry (~109° bond angles)
Carbon atoms are sp³ hybridized

Other Representations

Bond-Line Structures (Line-Angle Formulas)

More efficient way to represent organic molecules Rules:

Drawn in a zigzag format
Each bend and end represents a carbon
Hydrogen atoms are not shown explicitly
Double and triple bonds are represented by two and three lines, respectively
Heteroatoms (e.g., O, N, Cl, etc.) and their hydrogens must be drawn

Nomenclature of Alkanes

Isopentane: Common name for a five-carbon alkane
IUPAC Systematic Name: 2-methylbutane
IUPAC rules provide a systematic naming scheme for organic compounds

Classification of Carbon & Hydrogen Atoms

To complement the IUPAC (i.e., systematic) naming scheme, other descriptors are used to define the bonding environment about a given atom (usually C). Consider the following alkane:

Primary (1°) carbon: Bonded to one other carbon/heteroatom
Secondary (2°) carbon: Bonded to two other carbon/heteroatoms
Tertiary (3°) carbon: Bonded to three other carbon/heteroatoms
Quaternary (4°) carbon: Bonded to four other carbon/heteroatoms
The same classification applies to hydrogen atoms, based on the carbon they are attached to