Aldehydes/Ketones and optical isomerism

Question 1

Describe how to dustinguish between separate samples of the two stereoisomers of CH3CH2CH2CH2(OH)CN

Answer 1

• shine polarised light through sample
• enantiomers rotate light in opposite directions

Question 2

Explain why a reaction produces a racemic mixture

Answer 2

• Planar carbonyl group
• has equal chance of being attacked on either side
• equal amounts of enantiomers made

Question 3

describe how propanone and propanal can be distinguishes using

a- chemical test (3 marks)

b- proton NMR spectra (2 marks)

Answer 3

chemical test
- add feelings solution
- propanal = brick red ppt
- porpanone = no reaction

proton NMR
- propanal = 3 peaks (3 proton env)
- propanone = 1 peak (1 proton env)