11.4 - Isomerism

Question 1

What are isomers? What are the 2 main groups of isomers?

Answer 1

Compounds that have the same molecular formula but are different molecules
Structural isomers = molecules with the same molecular formula but a different structure
Stereoisomers = molecules with the same structural formula but a different spatial arrangement of atoms

Question 2

What are the 3 structural isomers and definitions?

Answer 2

Chain isomers = different number for the carbon chain
Position isomers = functional groups can be in different positions on the carbon chain resulting in isomers
Functional group isomers = same molecular formulae but contain different functional groups

Question 3

Which functional group changes in a compound to form the isomer of an alkene?

Answer 3

Changes from an alkene group to a cycloalkane
E.g. butene -> cyclobutane (C4H8)

Question 4

Which functional group changes in a compound to form the isomer of an aldehyde?

Answer 4

Changes to a ketone
E.g. propanal -> propone (C3H6O)

Question 5

Which functional group changes in a compound to form the isomer of an carboxylic acid?

Answer 5

Changes to an ester
E.g. ethanoic acid -> methyl methanoate
NOT A POSITION ISOMER! As for it to be carboxylic acid the functional group needs to be on the end and for an ester it is always in the middle

Question 6

Which functional group changes in a compound to form the isomer of an alcohol?

Answer 6

Changes to an ether
E.g. propan - 1 - ol -> an ether… (C3H8O)

Question 7

What is an E isomer?

Answer 7

The highest priority group on each carbon atom is on opposite sides

Question 8

What is a Z isomer?

Answer 8

The highest priority group on each carbon is on the same side

Question 9

What is cis/trans isomerism?

Answer 9

Type of E/Z isomerism where the two substituent groups are the same
Cis = the two groups are on the same side
Trans = the two groups are on opposite sides

Question 10

How do you find which is an E/Z isomer?

Answer 10

1. Look at the 2 carbons in the carbon bond
2. One with higher atomic mass is the group you care about
3. Look to see if they are on the same or opposite sides

Question 11

What are the conditions for being an E/Z isomer?

Answer 11

• must have a double bond: restricted rotation around planar
• must be different groups on each carbon