What does a chelating metal do to the substrate shape?

• It destroys the stereocentre
• It locks the new shape
• It removes the carbonyl

What does the standard open-chain model assume about the biggest neighbour?

• It sits away from the carbonyl
• It sits on top of the carbonyl
• It bonds to the reagent

On a rigid ring, attack direction is predicted from axial and equatorial approach arguments.

Circle one:   True   False

Adding a chelating metal flips the major product. What happened?

• The reagent changed its charge
• The other face opened
• The stereocentre was erased

An alpha-substituted aldehyde meets hydride with no metal present. Which product dominates?

• The one from attack on the more blocked face
• An equal mix of both diastereomers
• The one from attack on the less blocked face

A rigid cyclic ketone can be attacked from above or below the ring. How do you choose?

• Always pick attack from above
• Flip a coin, both are equal
• The less clashed path

A student applies the open-chain model to a chelated substrate and is surprised. What is the error?

• Using a model the conditions break
• Drawing the carbonyl at the wrong angle
• Forgetting to stir

Two models predict opposite faces. Which experiment distinguishes them?

• Add or omit the metal
• Run it twice as long
• Use twice as much reagent