Tang 05 aromatic hydrocarbons
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The document discusses aromatic hydrocarbons, which contain a benzene ring as a base. Michael Faraday first isolated benzene from gas lines in London. Most aromatic compounds are volatile and have distinct aromas. Benzene has a molecular formula of C6H6 and is a planar molecule with delocalized electrons shared around its six carbon ring. The IUPAC naming system for aromatic compounds is described, including naming compounds with substituents on the benzene ring and indicating their positions.
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Tang 05 aromatic hydrocarbons
- 2. AROMATIC HYDROCARBONS Aromatic hydrocarbons contain a benzene ring, C6H6, as a base Michael Faraday first isolated benzene from the oily residue that had collected in gas lines in London, England
- 3. AROMATIC HYDROCARBONS Most of these compounds are volatile (easily vaporized) and are associated with a distinct aroma (good or bad) Vanillin Cinnamaldehyde
- 5. STRUCTURE OF BENZENE - Molecular formula: C6 H6 - Structural formula consists of a 6-member carbon ring with 3 C=C double bonds - Benzene is a planar molecule
- 6. BONDING IN BENZENE The carbon-carbon bonds in benzene are all the same length which is evidence that the bonds are not true double & single bonds. The carbon-carbon bonds are all 139 pm which is intermediate between the length of a C-C single bond (154 pm) and a C=C double bond (133 pm; double bonds are shorter).
- 7. BONDING IN BENZENE - The electrons that make up the ‘double bonds’ in benzene are actually delocalized (shared) around all 6 carbon atoms - This arrangement is indicated by placing a circle in the centre of the 6-member ring
- 8. AROMATIC HYDROCARBONS methylbenzene chlorobenzene ethylbenzene IUPAC naming system: With side-chains, aromatic naming follows similar rules as for C-chains.
- 9. AROMATIC HYDROCARBONS IUPAC naming system: 3-phenylheptane When benzene is considered to be a side group, it is called a phenyl group
- 10. AROMATIC HYDROCARBONS IUPAC naming system: o-dimethylbenzene m-dimethylbenzene p-dimethylbenzene ortho meta para When only two groups* are present on benzene, the following prefixes are used: 1,2-dimethylbenzene 1,3-dimethylbenzene 1,4-dimethylbenzene *groups refer to any substituents other than hydrogen, and the two groups may be different from each other
- 11. AROMATIC HYDROCARBONS Solve these Rebus puzzles: