Optical Isomerism

Question 1

write a definition for structural isomerism

Answer 1

molecules with the same molecular formula but different structural formulas

Question 2

write a definition for stereoisomers

Answer 2

molecules with the same molecular formula and the same structural formula, but a different arrangement of atoms in space

Question 3

what is a chiral carbon molecule

Answer 3

a carbon atom that is surrounded by 4 different groups

Question 4

what are enantiomers

Answer 4

two molecules that are optically active and are super-imposable mirror images of eachother.

Question 5

give a definition for racemates

Answer 5

two enantiomers in equal quantities that rotate plane polarised light in equal and opposite directions. A racemic mixture is not optically active

Question 6

what type of reaction will give you a racemic mixture

Answer 6

electrophilic addition e.g. the formation of 2-bromobutane from but-2-ene. You will get a racemic mixture as there is equal chance of the nucleophile attacking from the top or the bottom of the double bond.

Question 7

give three methods that are used in medicine to resolve the problem that only one of the optical isomers is useful

Answer 7

• seperate the optical isomers
• sell as a mixture
• choose methods that will only make the desired optical isomer