Introduction to Organic Chemistry: Isomerism - Structural Isomerism

Question 1

Define the term structural isomerism

Answer 1

• When molecules have the same molecular formula but different structural formula

Question 2

What are the three types of structural isomerism?

Answer 2

• Chain isomers
• Functional group isomers
• Position isomers

Question 3

What are chain isomers?

Answer 3

• These occur when the atoms in the carbon chain are arranged differently but both molecules share the same functional group
• E.g butane and methylpropane are chain isomers of C4H10

Question 4

What are position isomers?

Answer 4

• These occur within the same homologous series when the functional group is on a different carbon atom
• E.g 1-chlorobutane and 2-chlorobutane are position isomers of C4H9Cl

Question 5

What are functional group isomers?

Answer 5

• These occur when the compounds have a different functional group
• E.g hex-1-ene and cyclohexane are both functional group isomers of C6H12

Question 6

How can you identify whether two compounds are isomers?

Answer 6

• If you can rotate C-C bonds and the models look the same – they are not isomers
• If you can rotate or turn over the whole molecule so that the models look the same – they are not isomers
• If you would need to break bonds and move atoms about to make the models look the same – then they are isomers