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A growing personal collection of M. E. Alonso Amelot, PhD.
http://alonso-amelot.yolasite.com

UPDATE TO FOLLOWERS OF THIS WIKI:
===This page will be discontinued in June 2018. Wikispaces is closing its business everywhere. Org chem problems below and additional ones will be trasferred to another page, currently under construction. I'll let you know the address soon.===

==This is an Organic Chemistry wiki for problems in organic reaction mechanism and discussing feasible solutions. This wiki is linked to the Self-org-chem webpage, a Resource Center for College/University Organic Chemistry located at==

Readers and fans of reaction mechanism will find interesting:
by prof MIguel E. Alonso Amelot
 * THE ART OF PROBLEM SOLVING IN ORGANIC CHEMISTRY **, 2nd Edition, Wiley 2014. 450 pp

Paperback or e-book editions are reasonably priced. Add to your cart at: http://eu.wiley.com/WileyCDA/WileyTitle/productCd-111853 0217.html or find it in Amazon books with a (+++++) 5 star ranking mong readers. Scores of mechanistic problems and hundreds of advanced chemical reactions at your fingertips, to become a professional problem solver. Unique indexing system to ease problem finding and reaction type.



===Below there is a list of mechanistic problems you may wish to tackle, one by one. Frequently new problems are added so be sure to visit this wiki frequently. Also, on the left strip menu, you may wish to go straight to problem Nº X if you have solved previous problems. Enjoy as much as I do with this wonderful game of problem solving, and keep your organic wits in good shape!===

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Let's begin with something not too difficult. Here is an accessible problem:
Level: second-third undergraduate org chem. First year graduate Difficulty: 4/10

TO SEE A FEASIBLE SOLUTION CLICK HERE OR GO TO 'PROBLEM 1' PAGE on the left menu Visit this wiki regularly for new problem entries.

__**PROBLEM 2**__
Level: first-second year graduate in organic chemistry Difficulty: 6/10 1,2-diazoheterocyclics like 1 are unstable upon heating, realeasing N2 gas. Some hints: 1) Electron donor groups (as MeO in this case) accelerate the reaction, and may take place at temperatures as low as 45ºC. 2) Electron attractors give chiefly products 2 & 3 with only a trace of 4. In such cases, 2 is the major component of the product mixture 3) Upon heating, cyclopropane 3 rearranges to 4, but not 2. TO SEE A SOLUTION GO TO 'PROBLEM 2' PAGE on the left menu or CLICK HERE.

__PROBLEM 3__
Source: S. Ma et al, JOC 2003; 68, 8996-9002 Level: second-third semester undergraduate org chem. First year graduate Difficulty: 3/10

To see a solution go to Problem 3 page or click HERE

__PROBLEM 4__



Source: Ihara M, Taniguchi M,Tokumaga Y, Fukumoto K 1994, JOC **1994**, //59//, 8092-8100 Level: third semester undergraduate org chem. First year graduate Difficulty: 6/10

To see a solution to this problem go to Problem 4 on menu at left or click HERE

=__PROBLEM 5__=

Level: third semester undergraduate org chem. First year graduate Difficulty: 3/10 For a solution click this PDF tag: or go to Problem 5 on the left menu

=__PROBLEM 6__=

Source: Mellor, J. M., Merryman, G. D., Riviere, P. **Tetrahedron Lett //1991,//** 32, 7103-7107

Difficulty: 4/10
For a discussion and solutions to this set of reactions, click this PDF tag or go to Problem 6 on the left menu:



Hint:Before going to the solutions page, please look at products in terms of reactants. You will notice that in this one-pot reaction, reactants operate in more than one way...

__ PROBLEM 7 __ Level: second-third semester of undergrad org chem, first year graduate. Difficulty: 5/10

For a solution and discussion click on the following PDF tag:



or go to Problem 7 on the left menu

=__PROBLEM 8__= Source: García-Martínez AG et al. //Chem. Ber.// 1985, //118¸//1282

Level: 2nd year of organic chemistry undergraduate; 1st year graduate student
Difficulty: low-med, 4/10

For a discussion of this problem click on the following PDF tag or go to left menu and click on Problem 8 file.

=__PROBLEM 9__=

Source: A. García-Martínez et al. //Tetrahedron// **1996**,//52//, 7973-7982.

DIFFICULTY: low-mid, 4/10 LEVEL: third semester undergraduate org chem., 1st y. graduate

For a discussion of this problem click on the following PDF tag or go to left menu and click on Problem 9 file.


 * __ PROBLEM 10 __**

Source: He, P., Zhu, S. **2005**. //Tetrahedron// 61, 12398 – 12404. LEVEL: Advanced undergraduate, 1st – 2nd year graduate student DIFFICULY: 6/10

For a discussion of this problem click on the following PDF tag or go to left menu and click on Problem 10 tag. .

=PROBLEM 11=



LEVEL: mid undergraduate DIFFICULTY: 3/10

For a few hints and couple of solutions of this problem click on the Problem 11 tag on the upper left of this page. If there is no need for hints and want to go straightto the solutions then click below

=PROBLEM 12=

LEVEL: upper undergraduate - beginning graduate DIFFICULTY: 3/10 for compound **3**, 4/10 for compound **4**

For a few hints and couple of solutions of this problem click on the Problem 12 tag on the upper left of this page. For the full discussion in PDF, click on the tag below

=PROBLEM 13= LEVEL: graduate in org chem DIFFICULTY: 7/10 depending on how familiar you are with cyclopropane chemistry.

Not an easy problem. Some planning will be necessary before you begin bond connections and disconnections
HINT #1: Count carbons in compounds **1** and **2**, compare and decide whether this is just a skeletal rearrangement or alkylation jumps in.

HINT # 2: Use a string of three methylenes in **1** to help you identify reaction centers

Once you have tried your best and discussed this with your pals, go to the menu at left and click on Problem 13 to have a look at an enticing discussion or possible solutions to this mechanism.

=PROBLEM 14=



LEVEL: Advanced undergraduate DIFFICULTY: 3/10 standard, but depends on your background,

The solvents-NaOH (anh) and 1 is heated for 6 hr. After cooling aq HCl is used for work up.

HINT 1: Aliphatic alcohols do not react HINT 2: While it is rather obvious that the gem-dimethyl fragment emerges from acetone (no better candidates around), the construction of the isobutyrate unit is a shed more difficult to imagine. Is there a second source of carbon to justify the extra carboxylate?

This is a relatively recent application of a century-old reaction created by prof. Guido Bargellini in Italy in the early 20th century and published in 1906. Today it carries his name. Bargellini's design is a precursor of the multicomponent reaction (MCR) so popular nowadays in the reaction chest of organic synthesis. Despite its old age, this is a rare and efficient procedure to build highly substituted ethers, esters and amines in yields above 70%. Learn more about this in the discussion of possible solutions, Go to Problem 14 or click the corresponding entrance on left margin above. But first, try your own ideas and discuss them with your pals. Once you find out the trick behind It will take you a few minutes to get the right answer.


 * PROBLEM 15 **

LEVEL: Mid undergraduate DIFFICULTY: 3/10

I'll keep hidden the literature source for a week or so, for you to work this relatively easy problem No matter how simple, the thing here is to quickly grab the difference of oxidation level between products 3 and 6, as you may have already noticed. Where does this difference come from?

On the other hand, the mechanism seems quite accessible and perhaps there are common features for the two reactions, except of course the substituents. The mineral acid and highly polar medium suggests the intervention of a specific type of intermediate I will refrain from revealing momentarily.