Formulas, functional groups and naming
Introduced| English | Meaning |
|---|---|
| hydrocarbon/ˈhaɪdrəkɑːbən/ | A compound containing only carbon and hydrogen atoms. |
| alkane/ˈælkeɪn/ | A saturated hydrocarbon containing only single bonds between carbon atoms. |
| functional group/ˈfʌŋkʃənl ɡruːp/ | An atom or group of atoms responsible for characteristic chemical reactions of an organic compound. |
Naming the carbon compounds
- A hydrocarbon 碳氢化合物 contains only carbon and hydrogen; alkanes 烷烃 are the simplest.
- A functional group 官能团 is the reactive part that decides a molecule's properties.
- We draw molecules in several ways and name them systematically.
Functional group lab
Sort organic molecules by the group that controls their reactions.
A functional group is:
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Molecules with the same functional group behave alike, because the group is the reactive part.
A group of atoms that gives an organic molecule its characteristic reactions is a ______ group.
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e.g. –OH, –COOH.
Types of formula
| Formula | What it shows |
|---|---|
| general | the pattern for a family — alkanes are $\text{C}_n\text{H}_{2n+2}$ |
| molecular | the actual atom counts — $\text{C}_4\text{H}_{10}$ |
| structural | the groups in order — $\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_3$ |
| displayed | every atom and bond drawn |
| skeletal | lines for bonds; carbons at corners, H on carbon hidden |
Chain, positional and functional-group structural isomerism
The general formula of the alkanes is:
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Alkanes follow CₙH₂ₙ₊₂ (e.g. C₄H₁₀ for butane).
In a skeletal formula:
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Skeletal formulas use a zigzag of lines; carbon atoms are the corners/ends and their hydrogens are implied.
Match each organic term to its meaning.
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Each item links the term to its correct meaning.
Naming
- A stem for the carbon count: meth- (1), eth- (2), prop- (3), but- (4), pent- (5), hex- (6).
- An ending for the functional group, and numbers to show where groups are.
Crude oil is a complex mixture of hydrocarbons
Which stem is used for a chain of four carbons?
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meth=1, eth=2, prop=3, but=4, pent=5, hex=6.
Naming pitfalls
- Number the carbon chain from the end that gives the functional group the lowest number.
- Check the suffix matches the family: -ane, -ene, -ol, -al, -one, -oic acid.
You've got it
- a functional group is the reactive part; same group → similar properties
- formulas: general ($\text{C}_n\text{H}_{2n+2}$) / molecular / structural / displayed / skeletal
- name with a stem (meth/eth/prop/but…) + an ending + numbers