Chapter 17 Flashcards
What is optical isomerism a type of?
Stereoisomerism
What is sterioisomerism?
Where isomers have the same structural formula, but the atoms are arranged differently in space
What is a chiral carbon atom also known as?
A chiral centre
What is a chiral centre?
A carbon atom that has 4 different groups attached to it
What are enantiomers also called?
Optical isomers
What are optical isomers?
Isomers which are mirror images of each other and come from chiral centres
What are the 2 steps you have to take when drawing optical isomers?
1-Locate chiral centres
2-Draw one enantiomer in a tetrehedral shape, then draw a mirror image of it
What is normal light made up of?
A range of different wavelengths and vibrates in all directions
What is monochromatic, plane-polarised light made up of?
Light of a single wavelength and only vibrates in one direction
As optical isomers are optically active, what do they do?
They rotate the plane of polarisation of plane-polarised monochromatic light
What do optical isomers do to plane-polarised monochromatic light?
One enantiomer rotates it clockwise whilst the other rotates it anticlockwise
What is a racemic mixture?
A mixture which contains equal quantities of each enantiomer of a chiral compound
Why don’t racemic mixtures rotate plane-polarised light?
The two enantiomers cancel out each others light-rotating effect
What do chemists often get when mixing 2 achiral things together?
A racemic mixture of a chiral product, as there is an equal chance of forming each of the enantiomers. For example, butane and chlorine form HCl + either enantiomer.
What happens in the Sn1 mechanism roughly?
You start with a single enantiomer and form a racemic mixture of 2 optical isomers of each other
What happens in step 1 of the Sn1 reaction?
A group breaks off, leaving a planar(flat ion). This group could be X-
What happens in step 2 of the Sn1 mechanism?
The planar ion can be attacked by a nucleophile from either side, resulting in 2 optical isomers
What happens in the Sn2 meachanims roughly?
A single enantiomer reactant produces a single enantiomer product
What happens in the only step of the Sn2 mechanism?
The nucleophile attacks the opposite side to the leaving group(X-), so only one product is produced. The product will rotate plane polarised light differently to the reactant
What do both aldehydes and ketones contain?
A carbonyl group
What is a carbonyl group?
A C=O bond
What is the difference between the structure of aldhydes and ketones?
Aldehydes have their carbonyl group at the end of the carbon chain, ketones have it in the middle of the carbon chain
What do aldehydes end in when naming>
-al
What do ketones end in when naming?
-one