[adeelonks]

I've really been racking my brain trying to figure this out, and even just some hints I would be grateful for


Ok so I made this diacid:



And then I'm going to dissolve it in concentrated sulfuric acid, and apparently doing so will result in an isomer of this diacid.
The only thing I can think of would be this sorta reaction:



Now, I was given an NMR of what the product will look like:
http://img245.imageshack.us/img245/16/95540608.jpg



But I can't decide whether I am completely off with what I am guessing might happen in this reaction or not. The ring structure is very rigid so there is a lot of different coupling constants acting on some of the hydrogen atoms.

The main thing that is bothering me is I don't see where in the NMR there is a signal for the alcohol in the mechanism I came up with (I'm not the best at reading NMR though).


Any thoughts about how this reaction might be working?


let me know if I'm not very clear about what is going on here.
Thanks a lot for any help

[adeelonks]

Was thinking maybe this reaction could happen as well producing a different isomer:


Is that a reasonable reaction at all?

Looking at the NMR, any carboxylic acid groups have to disappear upon reaction with sulfuric acid

[blind]

My hint for you is: How many different signals (and what they would look like) would you expect for the two isomers you've proposed?

[adeelonks]

Yea, I mean that was one of the first ways I've tried to look at it, but I can't think of a way for the reaction to go that would get rid of the carboxyl groups(while remaining an isomer) and at the same time give the same amount of unique NMR signals and splitting patterns to match the spectra given.

I feel like I'm just guessing different attacks that can happen to the diacid

[blind]

So from the NMR, you assume that there is no carboxylic acid - This is correct.  But to get the actual structure right (since you've posted two), you need to figure out how many unique signals you'd get your proposed structures.

[adeelonks]

Well I see 8 or 9 unique signals in the NMR I was given (though the signals upfield are kind of bunched together)

And with the products I came up with I'm seeing 8 possible unique signals for both of them (I think). Though that's assuming that because neither product is symmetrical that the only equivalent protons are protons that are on the same carbon and the two geminal hydroxyl protons.


Basically what I'm supposed to be doing is identify different reactions that could be occuring here, and then devise some chemical tests to identify which it is. I have no problem coming up with some tests though, that's not too difficult at all. I just can't tell if these reactions are even reasonable in the slightest or if I am way off.