[picoman]

Hello my Chemistry colleagues,

Organic Chemistry is not my strong subject and I am doing pretty well this semester. As the finals approaching my professor gave some exercises to practice on. Unfortunatelly I have stuck on the problem number 1. I am sure 95% that the second one makes sense (at least to me). The asterisk* shows the chiral centers of the molecules (When they are optically active). I worked backwards in order to determine the unknown structures in both exercises. The problem in the first exercise is the molecule with the =O and -OH groups in the right. I know that supplying ozone to the molecule it will break up through ozonolisis. Specifically:




But I cannot figure out clearly where they should bond with each other. By best quess was the formation of the ring with an alkene bond.


Prompt:



My answers.




If the images are not shown correctly I have uploaded both the exercises and my answers in my cloud drive. It does not contain any viruses. Please Trust me. I can not think any other way to upload them directly here:

https://mega.co.nz/#!n8giWRSB!L3wYCZ2sHZalslb-A776uepUIQdvH9iQy-drVEciMkI


I am sorry for my bad English. I am not a native speaker.

Thank you and I am waiting for your answers/suggestions. I hope I don't violate any of the forum's rules.

picoman

[kriggy]

Im not sure if your structure A is correct since one of the products is CO₂ which suggest isolated tripple bond at the end of chain. The possibility of tripple bond is further supported by product D where Lindlar catalyst is used to hydrogenate alkynes to alkenes.

In exercise two Im not sure that B is correct because if you go at its chemical formula then it has 4 more hydrogens which suggest total reduction of that tripple bond and this is also supported by used catalyst because if you dont use deactivated Pd/Pt catalyst you get total reduction of tripple bond to single bond

[picoman]

Thank you kriggy for the reply.

For the first exercise in particular the substitution is happening to one =O bond or in all of them? Because if there is substitution in all of them the rest of the parts does not make sense to me (D,E). Do I need to take into consideration the stoichiometry of the reaction?

[orgopete]

I agree with Kriggy. In 2, B is wrong, which also makes C wrong. Don't migrate the methyl.

In 1, I think there is an error, but I agree with Kriggy's sentiment. Reductive workup of ozonization should give formic acid, not CO2. Anyway, the bonds are not connected correctly. Count the carbons in joining the ring together.

[AromaticAcrobatic]

I agree with Kriggy. In 2, B is wrong, which also makes C wrong. Don't migrate the methyl.

I think Orgo means 2. D is wrong, as the methyl is missing. C looks okay. B is definitely wrong though.

Also, I can see you have the idea for 2 E but technically that 2 position isn't going to be major product from Br2 and hv.. Think markinokov.

This is a good exercise though, I like it!

 

[picoman]

I agree with Kriggy. In 2, B is wrong, which also makes C wrong. Don't migrate the methyl.

I think Orgo means 2. D is wrong, as the methyl is missing. C looks okay. B is definitely wrong though.

Also, I can see you have the idea for 2 E but technically that 2 position isn't going to be major product from Br2 and hv.. Think markinokov.

This is a good exercise though, I like it!

 

I agree with Kriggy. In 2, B is wrong, which also makes C wrong. Don't migrate the methyl.

In 1, I think there is an error, but I agree with Kriggy's sentiment. Reductive workup of ozonization should give formic acid, not CO2. Anyway, the bonds are not connected correctly. Count the carbons in joining the ring together.

Thank you so much for the answers guys! I think I have got it this time. But I have one more (and propably last) question. Sorry for being tiring. Could be 1A form an alykne and not a ring based on this? I am thinking this because of the constrain that could exist inside the ring. I am not 100% sure.

http://bit.ly/1s07tuM

Isn't what Kirby said?

Im not sure if your structure A is correct since one of the products is CO₂ which suggest isolated tripple bond at the end of chain. The possibility of tripple bond is further supported by product D where Lindlar catalyst is used to hydrogenate alkynes to alkenes.

In exercise two Im not sure that B is correct because if you go at its chemical formula then it has 4 more hydrogens which suggest total reduction of that tripple bond and this is also supported by used catalyst because if you dont use deactivated Pd/Pt catalyst you get total reduction of tripple bond to single bond

These are my updated answers:

[kriggy]

oh I might have not expressed myself clearly:
In 1 you need to have one tripple and one double bond since the molecule then breaks into COOH and CHO groups. I ment its ethynyl bond ie. -C≡CH

[picoman]

 

oh I might have not expressed myself clearly:
In 1 you need to have one tripple and one double bond since the molecule then breaks into COOH and CHO groups. I ment its ethynyl bond ie. -C≡CH

Hmmmmm but I can't get the correct number of hydrogen based on the empirical formula in C. Grrrr what I am doing wrong? 

[AromaticAcrobatic]

The starting material for 1 has to be cyclic, because of that aldehyde/ketone in the product.
Also, because there is an aldehyde and a ketone you should see that the alkene isn't symmetric.

I hope this helps!

 

[picoman]

I did my best. I don't know the end results of the reaction of alkyne (≡) with CH₂I₂