Reactivity 3.3: Organic Chemistry~ Aromatics, Benzene structure, Arenes

Structure of Benzene?

• Each cabon is sp² hybridized and forms 3 sigma bonds with angles of 120 degrees (planar)

• This leaves 1 unhybridized p electron on each carbon and the p orbitals effectively overlap in both direction

• So they spread out themselves evenly to be shared by all 6 carbon atoms (forming delocalized pi electron cloud-stable)

Nitration of Benzene

1. Electrophile is NO₂⁺ (nitronium ion) and has high activation energy.

2. Nitronium ion is attracted to pi electrons of benzene ring

3. 2 electrons from benzene are donated to nitronium ion forming a C—N while an electron form one N—O bond moves onto oxygen atom

4. Water acts as a base and accepts the H on the carbo-cation, restoring the ring and giving final product .

Naming arenes

• when benzene has lost 1 hydrogen (is a substituent). it is called a phenyl eg. 2-phenylhexane

Properties of arenes

• Unsaturated hydrocarbon that has a ring(cyclic) structure (1:1 ration of CH)

• Generally NON-polar (due to symmetric structure)