U3-2 - Stereochemistry Flashcards
When can geometric isomers occur?
When there is a lack of free rotation around a C to C bond, e.g. C=C or ring structure.
Is this isomer cis or trans?
Cis
Is this isomer cis or trans?
Trans
Why is this isomer cis?
Both substituents (CH3) on the same side of the double bond.
Why is this isomer trans?
Both substituents (CH3) on opposite sides of the double bond.
Why does propene not have geometric isomers?
Propene has two hydrogens attatched to the first carbon of C=C.
Will cis or trans isomers have the higher melting point?
Trans
Why do trans isomers have higher melting points?
Closer packing due to their shape allows for stronger IMF.
Chiral carbon/chiral centre
A carbon with four different substituents attached to it.
Optical isomers/enantiomers
Non-superimposable mirror images of each other.
Racemic mixture/racemate
50:50 mix of enantiomers
(50% R, 50% S)
How can you tell apart two separate samples of different optical isomers?
They rotate plane polarised light by the same amount in opposite directions.
Non-superimposable mirror images of each other.
Optical isomers/enantiomers
50:50 mix of enantiomers
(50% R, 50% S)
Racemic mixture/racemate
