[Burningkrome]

Hey,

I'm reviewing my organic chem as prep for taking Organic 2. Its been a while, so I'm using the book "Organic chemistry as a second language". It’s awesome, but I had a question about why one of the problems chose the synthesis method it did.

I actually have two questions that relate to it. (See image).

The first question related to item one in the image. Fairly simple and I just want some confirmations. You can remove an OH group and force the ring BACK into a double bind by adding concentrated acid (in this case HCL). However, it seems the reaction would proceed immediately from the OH -> double bond -> Hydro-Clorination (as shown in item 1).

Question: Is this/is this not the case? If it IS the case, how would you go about halting the reaction at the alkene and preventing the chlorination?

Second…the question in the book (11.83…for any of you who have it) was to move the OH group from the less substituted carbon to the more substituted carbon. (See image).

I selected to use a concentrated acid (version 3) however the book chose to use a tosylate with EtO- to replace the OH, and then hydrobrominate.

Question: Why? The H2SO4 solution seems much much simpler and easier for the lab. Is it too inefficient? Too low a yield? Would it not work this way?

Thanks for the help

[orgopete]

Since I am not seeing any images, I am only guessing.

Example 1, a problem with doing an elimination with HCl (HBr or HI) is the protonation will occur okay. Then the next step may be an SN2 reaction depending on the substitution pattern. A primary will likely undergo an SN2 rather than form a alkene.

Secondly, if you want to form an alkene, it helps to heat the reaction. Aqueous HCl is less dehydrating and heating bleeds out the HCl.

Example 2, sounds like a migration?

Sulfuric too simple or yields too low, could be. Without seeing the reaction, it may not even give the product.