New groups and naming aromatics
| English | Chinese | Pinyin |
|---|---|---|
| amide | 酰胺 | xiān àn |
| aromatic | 芳香 | fāng xiāng |
| benzene ring | 苯环 | běn huán |
| phenol | 苯酚 | běn fēn |
| aliphatic | 脂肪族 | zhī fáng zú |
A whole new ring of chemistry
- At A Level you meet more functional groups, including the amide 酰胺 and aromatic 芳香 compounds.
- Aromatic compounds are built on a benzene ring 苯环.
- They are named using the ring as the parent.
Aromatic naming lab
Classify aromatic substituents by how they are named.
Which new functional group is introduced at A Level?
A Level adds groups such as the amide, plus aromatic chemistry.
A compound containing a benzene ring is described as ______.
Aliphatic compounds have no benzene ring.
Benzene has the molecular formula C₆H₆.
Six carbons in a ring, each with one hydrogen.
Aromatic compounds
- Benzene is a ring of six carbons; aromatic compounds are built on it.
- As always, the functional group decides the properties, read from the formula.
Evidence that benzene is stabilised by delocalisation: it releases far less on hydrogenation (-208 kJ/mol) than the Kekule model predicts (-360 = 3x cyclohexene), so it is about 152 kJ/mol more stable than expected
Aromatic compounds are built on a:
Aromatic compounds contain a benzene ring; new families also include the amide group.
Naming
- Use the benzene ring as the parent and number the substituent positions.
- e.g. 3-nitrobenzoic acid (a $\text{–NO}_2$ on carbon 3), 2,4,6-tribromophenol (three Br on a phenol 苯酚 ring).
Name aromatics from the benzene ring, numbering the substituent positions from the main group at carbon 1
When naming an aromatic compound, you:
e.g. 3-nitrobenzoic acid puts a –NO₂ on carbon 3 of the ring.
Aliphatic 脂肪族 vs aromatic
- Aromatic compounds contain a benzene ring; aliphatic ones do not.
- Aromatic naming uses 'phenyl' and 'benzene' as the parent.
You've got it
- new groups at A Level include the amide and aromatic (benzene-based) compounds
- aromatic compounds are named with the benzene ring as the parent, numbering the substituents
- the functional group still decides the properties