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#1 2008-11-02 07:38:11


Mechanism of amide from acid chloride

OrganicChemistryMessageBoard Question

I don't get which nitrogen would attack the carbocation. Would it be N2O or NH2? Why?

You may have missed the following mechanism.
This example taken from A Guide to Organic Chemistry Mechanisms.

And now, a word from the sponsor. I have advocated that students solve problems mechanistically. In my classes, students have been able to raise their grade by what I would estimate to be a full letter grade each. This was evidenced by an improvement on the ACS exam. The class average improved by 20 percentile points.

How did I do it? I did two things. One, as you might guess, I emphasized reaction mechanisms. The other, I made reaction mechanisms easy for students to learn. A mechanism is a logical and understandable explanation of how and why a reaction occurs. The questioner's question implies an indifference to the mechanism. That is, if one is pattern matching reactions, why would one choose one nitrogen atom over another? If you were to write out the structures, the first step in writing a mechanism, only one of these nitrogen atoms has available valence electrons. Since it is the valence electrons that are attracted to the most electron deficient carbon, that is the nitrogen that attacks. You can see in the mechanism above that a new bond forms between the carbon and nitrogen with the nitrogen donating the electrons.

I have been gathering data on student responses. Pattern matching is a prevalent pattern. It is what our brains are really good at. However, it is very unlikely a baseball player's lucky socks has any effect on his play, though it is not surprising that he might try to repeat every detail that preceded his lucky event. However, the more astute players are probably more aware that the spin on the ball is important to its path through the air and the more quickly they can perceive this, the better they can anticipate its trajectory.

So too it is with chemistry. The better a student can understand the factors that guide a reaction, the better they can predict the result. I have done a preliminary study to demonstrate that pattern matching was predominant in a class I taught the second half of. While I cannot guarantee all students they would do better by knowing how reactions actually occur, my classes have improved dramatically as I became more skilled in enabling students to learn reaction mechanisms.

If you wish to learn reaction mechanisms, I believe A Guide to Organic Chemistry Mechanisms is singularly the best guide available. You can review student testimonials to their success, examples of pages, how the book works, how it appeals to how our brains work, etc.

I believe it would be the best if your professor adopted the book for you to make the best use of it. However, the book is easy to use and learn from. While students are not happy to learn this in any class, students actually have to learn all subjects on their own. When it comes to the test, there will not be anyone to help them. That is where A Guide to Organic Chemistry Mechanisms is exceptionally good. It gives you the tools to solve problems.



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