Geometric IsomersGeometric Isomers

Lack of rotation around carbon-carbon double bonds has an important structural implication.

Lack of rotation around carbon-carbon double bonds has an important structural implication.

These are not the same. Therefore, they cannot have the same name.

cis-2-butene trans-2-buteneIf the hydrogens are on the same side it

is a cis configuration. If they are on opposite sides of the double bond it is a trans configuration.

These are not the same. Therefore, they cannot have the same name.

cis-2-butene trans-2-buteneIf the hydrogens are on the same side it

is a cis configuration. If they are on opposite sides of the double bond it is a trans configuration.

Name each:Name each:Cis-2-pentene

1-pentene

Trans-2-pentene

Name it:

C-C-C-C-C=C-C C H H

5-methyl-cis-2-heptene

Name it:

C-C-C-C-C=C-C C H H

5-methyl-cis-2-heptene

StereoisomersStereoisomersMolecules of the same molecular structure

that differ only in the arrangement of atoms in space.

What does this mean?You need to understand 2 terms:1. SuperimposableObject is symmetrical - mirror image is no

different then original.Ex- ball

2. NonsuperimposableMirror image cannot be placed on top of

originalEx- your hands

Molecules of the same molecular structure that differ only in the arrangement of atoms in space.

What does this mean?You need to understand 2 terms:1. SuperimposableObject is symmetrical - mirror image is no

different then original.Ex- ball

2. NonsuperimposableMirror image cannot be placed on top of

originalEx- your hands

StereoisomersStereoisomersA chiral carbon isasymmetrical when it has 4

different groups.ex - CHFClBrWhere is the chiral carbon?

C-C-C-C-C-C-C C C

A chiral carbon isasymmetrical when it has 4

different groups.ex - CHFClBrWhere is the chiral carbon?

C-C-C-C-C-C-C C C