optical isomerism

Question 1

how can we distinguish between 2 optical isomers

Answer 1

plane polarised light will be rotated by both the enantiomers in opposite directions clockwise and anticlockwise but by the same amounts

Question 2

why would the reaction containing a c=o bond be a raecmic mixture

Answer 2

because of the PLANAR CARBONYL GROUP. this can be attacked from both sides both above and below the carbon and therefore there is an equal probability of forming the 2 enantiomers in the equal amounts

Question 3

explain how this raecmix mixture is formed

Answer 3

planar molecule, equal probability of attack from above and below

Question 4

deduce the role of ethanal in step one step two the reac?

Answer 4

proton donor - nucleophillic addition

Question 5

In practice, KCN rather than HCN is added to the carbonyl compound.
Given that Ka for HCN = 4.0 × 10–10 mol dm–3, suggest why the reaction with HCN is
very slow.

Answer 5

Weak acid

Question 6

standard light vs plane polarised light

Answer 6

standard light oscillates in all directions, plane polarised light oscillates in one direction. light is passed through a polaroid filter

Question 7

why can we not adapt a reac to only produce one enantiomer

Answer 7

because it is very expensive

Question 8

tollens

Answer 8

add aldehyde or ketone to tollens and place this in a hot water bath. do not use a bunsen burner as aldehydes and ketones are flammable.