Organic Chemistry Basics
25min Part 4 / Ch7 / Lesson 1
Prerequisites: 1-1-4
Objectives
- Describe characteristics and classification of organic compounds
- Classify hydrocarbons (saturated/unsaturated, chain/cyclic)
- Understand the concept of isomers
What Are Organic Compounds?
Organic compounds: compounds with carbon skeletons (excluding CO, CO₂, carbonates, etc.).
Characteristics:
- Made of covalent bonds (not ionic)
- Generally low melting/boiling points
- Often insoluble in water, soluble in organic solvents
- Combustible (complete combustion produces CO₂ and H₂O)
Classification of Hydrocarbons
| Type | General formula | Bonding | Examples |
|---|---|---|---|
| Alkanes | CₙH₂ₙ₊₂ | C-C single bonds only | Methane CH₄, Ethane C₂H₆ |
| Alkenes | CₙH₂ₙ | C=C double bond | Ethylene C₂H₄ |
| Alkynes | CₙH₂ₙ₋₂ | C≡C triple bond | Acetylene C₂H₂ |
Main types of hydrocarbons
Isomers
Isomers: compounds with the same molecular formula but different structures.
- Structural isomers: different connectivity of atoms
- Geometric isomers (cis-trans): different arrangement around a double bond
Example: Structural isomers of
- Butane (straight chain): CH₃-CH₂-CH₂-CH₃
- 2-methylpropane (branched): (CH₃)₃CH
Check Your Understanding
Q1 The general formula for alkanes is:
Q2 Hydrocarbons with C=C double bonds are called:
Q3 How many structural isomers does C₄H₁₀ have?
Exercises
Q1. Draw all structural isomers of and name them.
Solution
Three isomers:
- Pentane: CH₃-CH₂-CH₂-CH₂-CH₃ (straight chain)
- 2-Methylbutane: CH₃-CH(CH₃)-CH₂-CH₃ (one branch)
- 2,2-Dimethylpropane: C(CH₃)₄ (neopentane)