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Hydrocarbon Rings

Chemistry 122/121

Cyclic Hydrocarbons

Both saturated and unsaturated hydrocarbons may be found in the form of a ring

The resulting structure has two less hydrogen than its straight chain counterpart

Butane = C

4

H

10

Cyclobutane

= C

4

H

8

Aromatic Hydrocarbons

Historically, these compounds all had an odor associated with them

They may contain a single ring or group of rings

Benzene

is the simplest aromatic

all examples of aromatics have a structure comparable to benzene

Another name for them are

arenes

The Structure of Benzene

Benzene is a six carbon ring with a hydrogen atom attached to each carbon

This leaves each carbon available to make a double bond

A maximum of three double bonds can form within the ring

As a result, two diagrams can be written to represent all the places a double bond can exist within benzene

Page 710

Resonance

As a result of double bonds being found in more than one place, the bonding e- between carbon atoms are shared evenly around the ring

Resonance allows the structure to be more stable

Benzene is less reactive than its

alkene

counterpart

Substituted Aromatic Hydrocarbons

Compounds that contain

substituents

attached to a benzene ring are called derivatives of benzene

When the benzene ring is the substituent, it is called a

phenyl

group

Benzene rings that have two

substituents

are called

disubstituted

benzenes

The positions of the

substituents

can be in the 1, 2 (

ortho

), 1,3 (meta), or 1,4 (

para

) position

For the remainder of class…

Complete Guided Reading 22.4

Practice Problems – use to review

Interpreting Graphics – 22.4