Chirality and optical isomerismEdexcel International A Level Chemistry: Mind map

Exam questions on Chirality and optical isomerism

1. Lactic acid (2-hydroxypropanoic acid), CH₃CH(OH)COOH, is made by muscle cells during hard exercise and by bacteria in yoghurt production.
   Explain why lactic acid shows optical isomerism and what is meant by its optical isomers.2 marks
2. Ibuprofen, (CH₃)₂CHCH₂C₆H₄CH(CH₃)COOH, is a painkiller that is sold as an equal mixture of its two optical isomers, although only one of them is pharmacologically active. Optical activity is measured in a polarimeter using plane-polarised monochromatic light.
   Explain why the equal mixture of ibuprofen isomers has no effect on plane-polarised light.2 marks
3. Two samples of halogenoalkane, each consisting of a single optical isomer, are hydrolysed by heating with aqueous sodium hydroxide. Compound X, 3-bromo-3-methylhexane, CH₃CH₂C(CH₃)(Br)CH₂CH₂CH₃, gives an alcohol product that does not rotate the plane of plane-polarised light. Compound Y, 2-bromobutane, gives butan-2-ol that does rotate the plane of plane-polarised light.
   Explain what the result for compound X indicates about the mechanism of its hydrolysis.3 marks