2. Aromatic Hydrocarbons

3. C6H6C6H6 Aromatic compounds contain a benzene ring(C 6 H 6 ) It is a very stable structure that is very hard to break. The most common reaction it undergoes is a substitution reaction. The hydrogens are switched for other substituents.

4. All benzene bonds between carbons in the ring are “a bond and a half”. Double bonds are very reactive. They will gladly accept another bond because they are unsaturated. For this reason, it is like there are no double bonds.   Resonance

5. Benzene is a chemical that is a colorless or light yellow liquid at room temperature. It has a sweet odor and is highly flammable. Benzene evaporates into the air very quickly. It is heavier than air. Natural sources of benzene include volcanoes and forest fires. Benzene is also a natural part of crude oil, gasoline, and cigarette smoke.

6. Industries use benzene to make other chemicals, plastics, resins, nylon, synthetic fibers, lubricants, rubbers, dyes, detergents, drugs, and pesticides. Benzene is damaging to our circulatory system, particularly the blood. Benzene causes cancer in humans.

7. We draw it like this. 1,2-dimethylbenzene Orthodimethylbenzene O-dimethylbenzene 1,2-dichloro-4- methylbenzene 1,4-dimethylbenzene Paradimethylbenzene P-dimethylbenzene 1,3-dimethylbenzene Metadimethylbenzene M-dimethylbenzene 1,2,3-trichloro-5-ethyl- 4-methylbenzene CH 3 CH 3 CH 2 Cl CH 3

8. Other forms of Benzene Rings

9. Sometimes a benzene is a substituent It is then called a phenyl. 3-ethyl-2,3-diphenyl pentane 3,3,4,4 tetrabromo-5,5-diphenyl-1-hexene

10. .l. Naphthalene has two rings How many hydrogen in this compound? Draw it. If every carbon has 4 bonds, each carbon has one double bond. The formula is C 10 H 8

11. The numbering system works like this: Notice the carbons in the centre are not numbered. Why?