Chapter 17 Problem 50 with mechanisms

Hi guys,

I worked out problem 50 and did the mechanisms in chemdraw. Notice in 50c and 50g that the amine on another molecule acts as the base, and this is why the problem specifies that there is excess of the amine.

Exam 3 Reaction Flashcards

For those of you who made a StudyBlue account or already had one, I made flashcards for our next exam.  See the link below to find them.

Exam 3 Flashcards

Bruce Chapter 17 #76 (a)

Many of the in-chapter problems in Bruice seem aimed at mastering basic skills and knowledge, while end-of-chapter questions often require integrating several areas of knowledge. I try to work through the in-chapter questions while reading along with the text, and then work the end-of-chapter questions.

Question 76(a) from the end of chapter 17 is especially good for practice. The question states: "Cardura, a drug used to treat hypertension, is synthesized as shown below. (a) Identify the intermediate (A) and show the mechanism for its formation.

When confronted with questions like these, it makes sense to assume the catalyst will play an important role in the first step - in this case, by deprotonating one of the hydroxyl groups. This creates an activated alkoxide ion which can then execute a nucleophilic attack on a susceptible carbon.

The big question in this case is, "which carbon?" We have, for the most part, been attacking the carbonyl carbon. This occurs because the resonance structure of the carbonyl group draws elecrons away from the carbonyl carbon, creating a slightly positive electrophilic charge.

However, there's a trick in this question. We have to recognize when a carbonyl carbon might not be the primary electrophile. In this instance, the alpha carbon (or Carbon 2) is more susceptible to nucleophilic attack. The ester group draws electrons away from the alpha carbon, which is then attacked by the activated alkoxide ion.

After the addition of more base and a second deprotonation, the molecule then undergoes an intermolecular reaction. The second alkoxide ion attacks the beta carbon and the bromide leaves. 

The final part of the reaction involves hydrolyzing the ester. The process here is shown in one step, but drawing out the full mechanism of the final step is excellent practice.

Ch. 17, #53

I worked through problem #53 for Ch. 17, so here you go.

The problem states:
Because bromocyclohexane is a secondary alkyl halide, both cyclohexanol and cyclohexene are formed when the alkyl halide reacts with hydroxide ion.  Suggest a method to synthesize cyclohexanol from bromocyclohexane that would form little or no cyclohexene.

Study Tip for the Next Exam

Fellow Organic Chemists,

In light of our upcoming, reaction-intensive exam, I'd like to share a tip that has been helping me since Day 1 of Orgo: copying down pre-solved syntheses problems, reagents and all, to study how certain things are turned into certain other things.

I usually focus hard on the sections in the book that say "Designing a Synthesis," because they show very clearly how reagents are used to turn one thing into another.  I also use the Sapling synthesis problems to do the same thing.  After I get them wrong a few (dozen) times, I hit the "Review Answer" tab and see exactly what was done.  This way, I can have a list of reactants, reagents, and products at my disposal when faced with a really difficult synthesis problem.

Here's a good example from page 681 of Bruce:

This example is beautiful because it shows you very clearly how to add several different things to benzene, and which order they should be added in to get a desired product. So for studying purposes, I like to think through many of these without even necessarily trying to solve them. If I can see how to do certain things, I can be ready for the synthesis problems on the tests and quizzes. Hope this tip helps.

Esterification Reactions in Wine.

      Esterification reactions were recently covered in class, specifically the Fischer Esterification.  This type of reaction occurs in wines after they have fermented and acetic acid is present to form ethyl acetate.  The ethyl acetate formation occurs when there is too much acetic acid in the wine and the esterification reaction takes place with the ethanol.  The result is a smell similar to nail polish or varnish in the wine and its considered a fault in the wine.  The article linked states that the reaction is catalyzed by a free hydrogen cation or a hydrogen from the acetic acid; I've used both in my drawing of the mechanism.  In the Fischer Esterification example we went over in class HCl was used to protonate if you want to compare.
Here are links to the article and also a wikipedia page with more info on wine faults:
Article  Wikipedia page
Ramey, Ough. "Volatile ester hydrolysis or formation during storage of model solutions and wines" J. Agric. Food Chem, 1980.

This is my first time using ChemSketch so please let me know if there are any improvements I can make and if there are any mistakes in the mechanism.

Question 30 in Chapter 17

This is my answer to problem 30. If there anything wrong, please correct me. Thank you.

PS: I can't put the number 18 as a superscript, but just so you know that it is just a label, not 18 oxygen. 

question about the notes 3/25

Hey guys,
I must not have written it down....but why does the acid anhydride (when reacted with the chlorine ion) not form the product with chlorine, but instead revert back to the starting material??

Detailed Solution for problem #33, ch. 16, p.689

The problem states that Diazomethane can be used to convert a carboxylic acid into a methyl ester. Propose a mechanism for this reaction: 

I hope this is helps.  please correct me if you notice any mistakes.

Sapling Homework Hint - #19

 Frank,

Here's some help with Question 19 from the Sapling Homework.

To find the mechanism, you need to go back to Chapter 15 - Aromaticity & Reactions of Benzene. This particular reaction is Bromination, which can be found on p. 639. The last two steps look as follows:

 I had to do this problem a couple times and couldn't figure out where I went wrong. Here's a couple hints:

1. Make sure all Br molecules have the right number of unpaired electrons.
2. Make sure the charges are correct on the electrophile.

Also, the book uses the abbreviation B: for base. I've always used, H20, but for this problem, Sapling wants you to use FeBr4 as the base. You don't need to include HB+, HBr, or HB: in either of the two last answers.

Hope this helps!

Sapling homework

Hi guys,
Can anyone help me in moving arrows for Q.19 of sapling homework?
I am stuck with the final step where a base picks the hydrogen from benzene and the electrons from that bond forms the double bond. Is the base FeBr4 and how do you form HBr and FeBr3? The mechanism was not shown in the book but we   have to show it on sapling.

Thanks.

Students Berate Organic Chemistry

We've all been there with Organic Chemistry... hitting our heads against the wall after countless hours of trying to figure out a synthesis problem or memorize all the steps for a certain mechanism. Yesterday, I came across a website that publishes student evaluations of their professors and courses at the end of each semester. I've posted a few of the best responses below. I hope you enjoy them as much as I did.



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Organic Chemistry Humor (2)

I thought that this is a fun way to remember that PCC is effective in oxidizing primary alcohols into aldehydes, whereas for secondary alcohols, it oxidizes them into ketones.

Another funny picture that I found of the internet is this:

( if you're familiar with the french story Le Serpent Boa from the collection Le Petite Price, I think you'll find this even more amusing...)