stereochemistry

Conformational stereoisomers

• diff conformations of the same molecule

• Interconvert easily

Configurational stereoisomers

• identical groups differ in how they are arranged around same central carbon

• Do not easily convert

• Need to break a bond to interconvert

Newman projection

View from end

Two forms of Newman configuration

Eclipsed

Staggered

Ecclipsed conformation

neighbouring atoms are alligned (0)degrees)

Staggered conformation

Neighbouring hydrogens at 60 degree angle

How to name stereoisomer

1. Assign order of priority

2. View molecule opposite side of group wit( lowest priority

3. If order of decreasing priority is in clockwise sequence then:R if anticlockwise: S

Anti conformation

• most stable

• Methyl groups far apart

Steric strain

Repulsive interactions between n odd atoms in close proximity

Due to rage groups close to each other

Torsional strain

Eclipsing of bonds on neighbouring atoms

Diastereoisomers

Two centres are opposite

Epimer

One centre is different