MChem Master of Chemistry Master of Chemistry: Organic Chemistry 5

Question 1

Which of the following correctly describes the Mitsunobu reaction?

Accepted Answer

It converts an alcohol to an alkyl halide with inversion via an SN2 mechanism using DIAD and PPh3

Answer

The Mitsunobu reaction uses DIAD (or DEAD) and PPh3 to activate the alcohol, and an acidic pronucleophile (HNu) then attacks with inversion of configuration.

Question 2

In mass spectrometry, what is the base peak?

Accepted Answer

The most abundant ion fragment peak, set to 100% relative abundance

Answer

The base peak is the most intense peak in the mass spectrum and is assigned a relative abundance of 100%; it may or may not correspond to the molecular ion.

Question 3

Which reaction converts a terminal alkyne to a methyl ketone via Markovnikov hydration?

Accepted Answer

Acid-catalyzed hydration with H2SO4/HgSO4

Answer

Mercury(II)-catalyzed hydration follows Markovnikov's rule and generates a vinyl alcohol (enol) intermediate that tautomerizes to the methyl ketone.

Question 4

What does a positive Tollens' test (silver mirror) indicate about a compound?

Accepted Answer

The compound contains an aldehyde (or alpha-hydroxy ketone)

Answer

Tollens' reagent ([Ag(NH3)2]+) oxidizes aldehydes (and some α-hydroxy ketones such as fructose) to carboxylates while reducing silver ions to metallic silver.

Question 5

In the Robinson annulation, which two reactions are combined to build a six-membered ring?

Accepted Answer

Michael addition followed by intramolecular aldol condensation

Answer

The Robinson annulation consists of a conjugate (Michael) addition of an enolate to an enone, followed by an intramolecular aldol condensation and dehydration to give a cyclohexenone.

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Master of Chemistry: Organic Chemistry 5