[scamp]

This one is driving me crazy- I just cant work it out.

Its a phenolic compound, C9H8O3 which can exist in two iosomeric forms.
Both forms decolourize permanganate, and on moderate oxidation yeild salicylic acid and oxalic acid as the only organic products.
One isomer loses water easily when heated , the other fails to dehydrate under the same conditions.

What can the compound be?

I keep going over and over the hints, but I cant identify it. Any ideas?

Thanks

[macman104]

Here are some things you can do to help guide you:

Calculate your elements of unsaturation, this should give you the number of double bonds or rings that are present.  You know that there is a benzene, which is 4.

Permanganate breaks up double and triple bonds, or hydrates those bonds.  The fact that you get 2 structures should indicate something.  How many structures would you get if you used cyclohexene?  If you take the two structures you get from the oxidation, and try and look at a way to combine them, there won't be many options available.

Two isomeric forms, what type of compound, related to the above information displays two different isomeric forms?

The information above is enough to generate the possible structure, the information about the dehydration is just fodder.  After the structure, I can sit here and theorize why one isomer undergoes dehydation and the other doesn't, but it didn't really provide me any information leading to the solution (but it did help confirm I suppose).

[scamp]

thanks, I think im getting closer but not quite!

It will have 6 degrees of separation, so 4 in benzene, and 2 other double bonds.  Two structures indicates that the permanganate breaks the double bond.

I just cant see how to combine the two structures to get something that fits the requirements...

[macman104]

It will have 6 degrees of separation, so 4 in benzene, and 2 other double bonds.  Two structures indicates that the permanganate breaks the double bond.

Good deduction.  While your thought that it is 2 other double bonds in this case can be correct, just wanted to point out that it could in some cases be other possibilities (but you may have known that).

Correct, the permanganate breaks the C=C double bonds.  When you oxidize, what resulting structure will you get.  If you were to perform this on 2-pentene, what two structures would you get. (Either draw them or somehow indicate what they are).

Going off of that (and looking at the relationship between the products and the structure of 2-pentene), we know that the product of the double bond cleavage is salicylic acid and oxalic acid.  Let's first consider where the double bond might have come from if we had salicylic acid and ethanoic acid.  Can you figure out what the original compound would have been to give those two fragments?  Can you extend this to oxalic acid instead of ethanoic acid?

If you're still confused, try and explain your thoughts to me so I can see what's tripping you up.  In case you aren't aware, I'm not intentionally being vague and not answering, but we try and operate on these forums by poking and nudging in the right direction instead of just giving answers.  Then the next time you get a problem, you'll have the tools necessary to deduce it yourself.

[AWK]

HO~C6H4-CH=CH-COOH  - three isomers, each can be Z(cis) or E(trans)

[macman104]

3 isomers?  I'm assuming by the ~ you mean it could be in the ortho, meta or, para position?  He said salicylic acid, which I assumed was the ortho isomer, no?

[scamp]

Thanks very much for your help,

I had been staring at the double bond for so along and I just couldnt see it. When I went through the oxidation of 2-pentene, then I could see how the double bond could break and form the double bond to O. I was just seeing it as forming two alcohol groups and not considering any further oxidation.

I have the ortho- position as it forms salicylic acid which has the OH group in the ortho position.
The cis- isomer will loose water, but trans will not as the groups cannot interact in trans..

I think!!

[spirochete]

I was following along with this problem and had a question.  The one thing I don't understand is what would be the mechanism for dehydration of the reactant?

[AWK]

I was following along with this problem and had a question.  The one thing I don't understand is what would be the mechanism for dehydration of the reactant?

This is a simple internal esterification

[spirochete]

ooooh yeah obviously. . .thanks