Topic 43: Alcohols - Reactions

43.1Alcohols are generally very stable compounds. Why is OH– never a leaving group?
 
43.2What is para-toluenesulfonic acid (pTSA), and why is it so useful?
 
43.3Why does exposing an alcohol to concentrated strong acid promote its reaction?
 
43.4The strong acids H2SO4 and pTSA catalyze the dehydration of alcohols. What is the mechanism of that reaction? [Use the generic species “H+” (like that, with quotation marks) to represent the actual proton donor, which is actually unknown, but is probably just H3O+.]
 
43.5Concentrated HCl is not generally used for the dehydration of alcohols. Why is that? Why does the reaction work with sulfuric acid but not HCl? Aren‘t both strong acids?
 
43.6By what mechanism do 2o and 3o alcohols generally react in the presence of concentrated aqueous HBr? Why don‘t we have to worry about H2O solvent competing with Br– as a nucleophile?
 
43.7Primary alcohols cannot undergo E1 or SN1 reactions. Yet they still react with HBr (and with HCl, if ZnCl2 is present as a catalyst). How does that work?
 

Topic 44: Alcohols - Carbocation rearrangements

44.1What is a carbocation rearrangement?
 
44.2Under what circumstances do carbocation rearrangements occur?
 
44.3What is the mechanism of this reaction? How do you explain the product distribution?


 
44.4Based on what you have now learned about the SN1 reaction, propose a mechanism for the following reaction:


 

Topic 45: Alcohols - Solutions to the problem that OH– is not a good leaving group

45.1What two reagents produce alkyl halides directly from alcohols without the use of strong acids?
 
45.2What is a tosylate, and how does its use solve the problem of OH– not being a good leaving group?
 
45.3How do you make a tosylate from an alcohol?
 
14 questions
364 questions for Organic I

364 Questions for Organic I

Dearest Student. This web page is a set of questions I call Detailed Intended Learning Outcomes For Organic Chemistry (Part I). 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 247 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)