Organic Chemistry C H H C C H C H H O C

Compare and contrast the structure of aromatic and aliphatic hydrocarbons. Include: molecular models, structural formulas, common uses Additional KEY Terms resonance

Aliphatics - straight chains and cyclic-aliphatics. Aromatics - benzene and its derivatives (variations) - unsaturated - named because of their smell/odour All aromatic compounds contain a single modified benzene ring or groups of rings.

Benzene (C6H6): simplest aromatic compound a known carcinogen colorless, highly flammable liquid naturally occurring in crude oil important industrial solvent and precursor in the production of drugs, plastics, rubber, and dyes…

Almonds Benzaldehyde C7H6O Citrus fruits Limonene C10H16

Optical Isomsers Spearmint / Caraway Carvone C10H14O

Liquorice Glycyrrhizin C42H62O16

6 electrons (one from each carbon) participate in double bonds. These 6 e- are actually shared by all 6 carbons. Two different correct structures for benzene - RESONANCE - to show the movement of the 6e-.

H C H H C C H C C H C H

H C H H C C H C C H C H

Molecules with double bond resonance are more stable than molecules of similar size. Explains higher than expected melting point.

Naming compounds containing Benzene 1. Benzene is the parent chain when the ring is off an end carbon of an alkane. CH3 CH2 - CH2 - CH2 - CH3 butylbenzene methylbenzene or "toluene"

Here the benzene ring is called a phenyl group Benzene is a branch on ANY alkene / yne chain, OR when the benzene ring is in the middle of the alkane chain. Here the benzene ring is called a phenyl group CH3 - CH2 - CH - CH3 2-phenylbutane CH2 - CH = CH2 3-phenylpropene

The Alkane exception to the Rule If there are two branches on an alkane, the alkane is the parent chain and the benzene ring is named as a phenyl. Even if the ring is on an end carbon CH2 - CH2 - CH - CH3 CH3 - 3-methyl-1-phenylbutane

When benzene has 2 identical branches on the ring, the positions are given special names. 1,2 - ortho 1,3 – meta 1,4 - para. H CH3 1,2-dimethylbenzene o-dimethylbenzene (o-xylene)

1,3-dimethylbenzene m-dimethylbenzene (m-xylene) 1,4-dimethylbenzene p-dimethylbenzene (p-xylene)

2-phenylbutane 3-phenylpropene methylbenzene butylbenzene CH3 - CH2 - CH - CH3 2-phenylbutane CH2 - CH = CH2 3-phenylpropene CH3 CH2 - CH2 - CH2 - CH3 methylbenzene butylbenzene

CAN YOU / HAVE YOU? Compare and contrast the structure of aromatic and aliphatic hydrocarbons. Include: molecular models, structural formulas, common uses Additional KEY Terms resonance