Alkanes
Vocabulary
| English | Chinese | Pinyin |
|---|---|---|
| saturated | 饱和 | bǎo hé |
| alkanes | 烷烃 | wán tīng |
| single bonds | 单键 | dān jiàn |
| substitution | 取代 | qǔ dài |
The saturated 饱和 hydrocarbons
- The simplest family of organic compounds is the alkanes 烷烃 — the main components of fuels.
- They are saturated: every carbon bond is single.
Practice
Alkanes are described as saturated because they have:
Saturated = all single bonds.
Practice
The general formula of the alkanes is:
Alkanes follow CₙH₂ₙ₊₂.
Practice
The simplest alkane is:
Methane has one carbon.
The alkane family
- Alkanes have the general formula CₙH₂ₙ₊₂.
- Examples: methane (CH₄), ethane (C₂H₆), propane (C₃H₈), butane (C₄H₁₀).
The first three alkanes; each member of the series adds a CH2 unit
Explore
Burning an alkane
Step through combustion. With plenty of oxygen an alkane burns cleanly; starve it of oxygen and you get toxic carbon monoxide and soot instead.
Practice
Because they have only single bonds, alkanes are relatively ______.
No spare bonds for addition reactions.
Saturated bonds
- "Saturated" means all the carbon–carbon bonds are single bonds 单键.
- There are no spare bonds, so alkanes are relatively unreactive.
Practice
Alkanes burn well, which is why they are used as fuels.
Combustion releases lots of energy.
Reactions of alkanes
- Alkanes burn well (combustion), which is why they are used as fuels.
- They are otherwise unreactive but can react with halogens in sunlight (substitution 取代).
Watch out
Saturated means single bonds only. Alkanes have no double bonds, so nothing can simply "add" to them. This makes them much less reactive than the alkenes.
You've got it
Key idea
- alkanes are saturated hydrocarbons (all single bonds), formula CₙH₂ₙ₊₂
- examples: methane, ethane, propane, butane
- they burn as fuels but are otherwise fairly unreactive