I see, that IS annoying! (extra torture for no reason)

Our prof is nicer, one of our true or false question was "Benzene is an example of an aromatic compound."

Originally Posted by jubilantx

the mechanism question molecule had an ester bit??? how come on my exam paper the bonds between the carbon and the oxygen were all single?

Oops, I meant ether.

Originally Posted by Alchemist11

Ummm I don't really remember the question perfectly but I can venture a guess:

You protonate one oxygen, and kick it off whilst forming a double bond with the other one. Then, this carbonyl, can be attacked by the other alcohol in the compound. This forms, I think it was a 6 membered ring, or something like that, and you deprotonate and then you're done.

The beauty of mechanisms is that you don't have to have done it before in order to solve it, nor do you have to have a name for it. Being able to get a mechanism has nothing to do with how much you studied, because it's never going to be an exact replica of an aldol or something of that nature. Instead, it just has to do with whether you've internalized the rules of the system and are able to apply those rules to devise or create things you've never seen before. And I guess that comes with practice.

Ha, I actually did exactly that! I suppose it was because the fact that I was devising something that I hadn't seen before that I didn't have enough trust in myself to believe I was on the right track. My answer seemed so short and simple for 7 marks. Thanks for clarifying!

I actually enjoyed writing the exam

Originally Posted by Alchemist11

Ummm I don't really remember the question perfectly but I can venture a guess:

You protonate one oxygen, and kick it off whilst forming a double bond with the other one. Then, this carbonyl, can be attacked by the other alcohol in the compound. This forms, I think it was a 6 membered ring, or something like that, and you deprotonate and then you're done.

The beauty of mechanisms is that you don't have to have done it before in order to solve it, nor do you have to have a name for it. Being able to get a mechanism has nothing to do with how much you studied, because it's never going to be an exact replica of an aldol or something of that nature. Instead, it just has to do with whether you've internalized the rules of the system and are able to apply those rules to devise or create things you've never seen before. And I guess that comes with practice.

I did something similar. It was only after I made that O bonded to the carbonyl leave that I realized I was onto the mechanism. I started at it for like ten minutes and then I was like "just gon protonate this shiz...." and it worked.

My synthesis was messed up, though. I eventually got a Br attached where the OCOCH3 should be, and then just threw some NaOCOCH3 at it. I'm pretty sure that's wrong. Maybe I'll get part marks...since I did get the rest of the molecule legitimately... the way I wrote it it even looked like I protected the other site by switching it to something else before throwing out Raney Ni...

Originally Posted by britb

I did something similar. It was only after I made that O bonded to the carbonyl leave that I realized I was onto the mechanism. I started at it for like ten minutes and then I was like "just gon protonate this shiz...." and it worked.

My synthesis was messed up, though. I eventually got a Br attached where the OCOCH3 should be, and then just threw some NaOCOCH3 at it. I'm pretty sure that's wrong. Maybe I'll get part marks...since I did get the rest of the molecule legitimately... the way I wrote it it even looked like I protected the other site by switching it to something else before throwing out Raney Ni...

I actually did the same as you, I used NBS and got a bromine at the position of the ester. I'm not sure if this was possible, but I reasoned because it was an allylic site. How did you uprotect with Raney Ni? Usually it's acid or something that pops off the weird acetal group...

As for the mass spec question, did anyone show their work? Did you need to? I just put the answer down...

Originally Posted by hatorade

I actually did the same as you, I used NBS and got a bromine at the position of the ester. I'm not sure if this was possible, but I reasoned because it was an allylic site. How did you uprotect with Raney Ni? Usually it's acid or something that pops off the weird acetal group...

As for the mass spec question, did anyone show their work? Did you need to? I just put the answer down...

I made the top side a alcohol or something (I can't remember...something that didn't react with HS--SH and friends) and then used the HS--SH, H2 Raney combo to fix the other one to be how I wanted it before getting the Br on... I didn't like it at all, but I had the MC to do.

I just put the answer for the Mass Spec too... the amount of space we were given didn't really suggest they wanted us to show our work... maybe we get points for C, H and the heteros?

I'm sooo lost.....why are u guys using proctecting group and raney nickel?
I didn't do that :S

Originally Posted by SandraM

I'm sooo lost.....why are u guys using proctecting group and raney nickel?
I didn't do that :S

There's usually a good three or four ways to do it... lol, I'm infamous for throwing out PBR3 and a Gingard as my epic finishing move... as long as you got the molecule I think you'll do ok.

I figured the quick and basic way to do it was to have the molecule cyclize and decarboxylate to form cyclopentanone. From there, a simple addition of CH3I gets you the alkyl group after enolate attack, followed by a reduction of the carbonyl to an alcohol, and fischer esterification in acid with acetic acid gets the product.

^ yaaaay exactly what I did! :')

i did that too...not

Originally Posted by Toast

I figured the quick and basic way to do it was to have the molecule cyclize and decarboxylate to form cyclopentanone. From there, a simple addition of CH3I gets you the alkyl group after enolate attack, followed by a reduction of the carbonyl to an alcohol, and fischer esterification in acid with acetic acid gets the product.

When I did my retrosynthesis I just stopped at cyclopentanone... I completely forgot about decarboxylation.. I should have kept going! FUUUUUUUUUUUUUU

Ohh p.s. what did you guys put for that MC question about phosphorous ylides? It was like, which of the following is not true, and it was just a bunch of long complicated words I had never seen before. I put that "they form alkynes" is not true because we've never seen them form anything but alkenes...?

And there was another one that was something like "how many possible products are possible from such-and-such aldol reaction, including stereoisomers and structural isomers: 0, 1, 2, 3, 4 or 5" ??

I put the alkyne one and 2