Isomerism

Question 1

What are isomers?

Answer 1

Isomers are molecules that have the same molecular formula but whose atoms are arranged differently

Question 2

What is structural isomerism?

What can structural isomers have?

Answer 2

Structural isomers are defined as having the same molecular formula but different structural formulae

structural isomers can have:

• the same functional groups attached to the main chain at different points - this is called positional isomerism
• functional groups that are different - this is called functional group isomerism
• a different arrangement of the hydrocarbon chain (such as branching) - this is called chain isomerism

Question 3

What is positional isomerism?

Answer 3

the functional group is attached to the main chain at different points

Question 4

What is stereoisomerism?

Answer 4

This is where two (or more) compounds have the same structural formula, however they differ in the arrangements of bonds in space

the two types are:

• E-Z isomerism
• optical isomerism

Question 5

What is E-Z isomerism?

Answer 5

E-Z isomerism tells us about the positions of the substituents at either side of a carbon=carbon double bond

the two substituents may either be on the same side of the bond Z (cis) or on opposite sides E (trans)

Question 6

Why can single bonds not be E-Z isomers?

Answer 6

the groups joined by a single bond can roate around the single bond, this does not occur around a double bond