[Thanatos912]

Hey all!

To begin I want to say I am not looking to have the answers given to me. I cannot understand, however, how six products are possible in this question.

http://www.austincc.edu/samorde/documents/Organic2Bonus1.pdf

I know there are differences in Sn1/Sn2 versus E1 and E2 but I cannot see how six are possible. The molecule indicates no specific stereochemistry...

I realize that in an Sn1/Sn2 -OMe will be my nucleophile, and that in an E1/E2 i will create a double bond...but how are six possibilities...possible? 

She gave us the hint that I will have to predict an Sn1 reaction which will rearrange giving 2 products, an Sn2 which will give one, an E1 which will rearrange to give 2 and an E2 which gives one....

[Thanatos912]

Basically, what I don't get is that in an Sn2 reaction I get an inversion of configuration...but since the halide group is attached to a ring, how does it approach it? Also, what rearrangement is possible for an Sn1 reaction, she said it will rearrange. I'm guessing she means a carbocation rearrangement but what group would change to give it a more sub'd carbocation?!?!! Crappy problem on her part, she did nothing to explain it.

[macman104]

Can you draw the compound in the chair conformation?  What conditions are required for an E2 reaction?

For the SN1, can you draw the carbocation that forms and also, what ways have you learned that carbocations can rearrange?

[orgopete]

From my experience, many students struggle with SN1, SN2, E1, and E2 reactions. It isn't that they should, but this problem exemplifies how or why it might be difficult. I also confess that I was a synthetic organic chemist so the objective of performing any reaction was to obtain a product in as high a yield as possible. It was counter to my purpose to run a reaction in which the mechanism to be performed should be unknown or questionable.

It occurs to me that the hand out was written in that manner. However, the clue does sensibly resolve this problem. That is, solve each problem sequentially. What are the possible SN1 products? Repeat with E1, SN2, and E2 elimination.

My rational for saying that is while it is possible to perform a reaction in which SN1 and SN2 reactions will compete with each other, generally you will chose one or the other. That is, if you wished to perform an SN2 reaction, you should use an SN2 solvent with high concentrations of nucleophile and halide. While an E2 elimination can and in this case will result in the major product, you would not expect to find the SN1 and E1 elimination reactions to any great extent (if at all). Similarly, if the sodium methoxide concentration is very low, then SN1 and E1 mechanisms will predominate and give a different spectrum of products.