Topic 25: Reversible addition to C=O: formation of cyanohydrins

25.1What is the dual role of HCl in the reaction of NaCN and a ketone to form a cyanohydrin?
 
25.2Why not just use HCN itself? (two reasons)
 
25.3Why might one tape a pill to the side of a hood one is working in when using HCN? See this report
 

Topic 26: Reversible addition to C=O: formation of imines and enamines

26.1What is an imine? How do you pronounce this name?
 
26.2While the mechanism given by your author is plausible, it is certainly not proven. Propose another valid mechanism for this reaction.
 
26.3Experimental evidence is that imine formation is pH-dependent. Why might that be?
 
26.4What is an enamine? How do you pronounce enamine?
 
26.5Equilibrium reactions generally need to be driven in the desired direction.
 
26.6What is an azeotrope, and how can the formation of an azeotrope assist in driving the enamine formation reaction?
 
26.7What is a Dean-Stark apparatus, and how could it be useful here?
 

Topic 27: Reversible addition to C=O: formation of hydrates and acetals

27.1Please do not get the impression from this section that the formation of hydrates from ketones is an important reaction. We are always careful to not use acetone in the presence of water and acids, but it isn‘t because of this. Do hydrates have any synthetic use?
 
27.2The formation of an acetal can be carried out by heating a ketone or aldehyde and an alcohol in the presence of a catalytic amount of p-toluenesulfonic acid in a solvent such as toluene that forms an azeotrope with water, with the collection of water using a Dean-Stark apparatus. Propose a mechanism for this reaction and explain why the reaction is carried out as described here.
 
27.3Why is the mechanism shown in Sample Problem 21.4 absolutely, definitively, not a viable mechanism for the hydrolysis of an acetal? (Besides the fact that the equations are not balanced.)
 
27.4How would you correct that mechanism, being careful to use balanced chemical equations?
 
27.5What is the driving force of the hydrolysis of an acetal, considering the fact that all the reactions are reversible?
 

Topic 28: Acetals as protecting groups for ketones and aldehydes

28.1Acetals, particularly the acetal made from ethylene glycol (1,2-dihydroxyethane) are famous as protecting groups for ketones. Why might that be? (two reasons)
 
28.2What is a 1,3-dioxolane?
 
28.3How is a 1,3-dioxolane protecting group removed?
 
28.4What are two examples of reactions where an acetal protecting group might be useful?
 
19 questions
472 questions for Organic II

472 Questions for Organic II

Dearest Student. This web page is a set of questions I call Detailed Intended Learning Outcomes For Organic Chemistry (Part II). Some time ago I asked myself, "Bob, what do you think are the key questions that you hope students will be able to answer after taking Chemistry 248 at St. Olaf College?" So here you have them. Some are very simple; some require more thought. All are good questions to be thinking about as you read, discuss, and master the practical aspects of organic chemistry. They are discussion starters and review tips. There are no answers here (though there are some clues). The questions are here to help you focus on what's important (to me, at least!) and organize your learning process. The questions are grouped into topics. Bite-size chunks. Take them a few at a time. Don't feast on them all at one sitting!

(preliminary version 2021.01.15 feeback: Bob Hanson)