Stereoisomerism: Geometrical Isomerism

Question 1

Stereoisomers are

Answer 1

compounds that have the same atoms connected to each other, however the atoms are differently arranged in space

Question 2

There are two types of stereoisomerism

Answer 2

Geometrical (E/Z) isomerism
Optical isomerism (this will be covered in the Second Year of the A Level course)merism

Question 3

Geometrical isomerism is seen in

Answer 3

Geometrical isomerism is seen in unsaturated (double bond containing) or ring compounds that have the same molecular formula and order of atoms (the atoms are connected similarly to each other) but different shapes

Question 4

E/Z nomenclature is used to distinguish between the isomers

Z isomers have functional groups on ………………

E isomers have functional groups ……………….

Answer 4

the same side of the double bond/carbon ring

on opposite sides of the double bond/carbon ring

Question 5

You may see this type of isomerism referred to in other sources as cis/trans isomerism

This is a special case of E/Z isomerism
A “cis” isomer would essentially be the same as a “………..” isomer and a “trans” isomer would also essentially be the same as an “,……..” isomer

Answer 5

Z

E

Question 6

This causes the compounds to have different

Answer 6

chemical and physical properties

For example, they may have different reaction rates for the same reaction (chemical property) or different melting/boiling points (physical property)

Question 7

How are priorities decided CIP rules

Answer 7

Separate the molecule in half at the C=C.

Assign each group a ‘priority’.

If the two groups with higher priorities are on the same side of the double bond,
then this is the z isomer. If the two groups with the higher priorities are on opposite
sides of the double bond then this is the E isomer.

Priorities are assigned by atomic number. The
atom with the highest atomic number has
higher priority.