Optical isomers questions
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Explain why Step 4 produces a racemic mixture.
M1 Got a planar shape M2 Equal chance (50/50) attack from above/below OWTTE Either side M3 Giving equal amounts of both optical isomers/enantiomers
Reaction 1 produces a mixture of W and two other isomers. Draw the structures of the two other isomers. Explain, by considering the mechanism of this reaction, why all three isomers are formed. Isomer w is 3 bromopropanenitrile
Stage 1 Types of Isomers formed 1a CH3CHBrCN 1b Exists as two Optical isomers / enantiomers Stage 2 Mechanism 2a 2 curly arrows 2b Intermediate structure primary carbocation OR Stage 3 Optical isomerism 3a 2-bromo isomer has chiral carbon / C with four different groups / non superimposable mirror images OR 3b Optical because (secondary) C+ planar 3c So can be attacked from above or below
(c) Identify the reagent that is warmed with isomer W in reaction 2. State the other reaction condition needed.
KCN Aqueous and ethanol
Describe how you distinguish between separate samples of the two enantiomers of the branched chain aldehyde C5H10O
Use Plane polarised light M1 rotates (the plane of) in opposite directions
Explain how a structural feature of this enzyme enables it to catalyse the hydrolysis of isomer G but not the hydrolysis of isomer F.
M1 Enzyme has an active site 1 M2 The G-Enantiomer / Enzyme has the correct stereo chemistry / stereospecific Or The G-Enantiomer / Enzyme has the complementary shape
Explain why the reaction produces a racemic mixture
planar Attack from either side With equal probability
justify why compound j does not show stereoisomerism.
Does not contain a chiral centre