Basic Synthesis

[Sciencegeeknm]

Hello,

 

I am a complete beginner to synthesis and wondered if someone knowledgeable would mind checking these steps to make 5-Bromo 3-hexanone

 

When you make the two molecules how is the carbon carbon bond formed to join them together and make the target molecule?

 

Thanks.

[Elite Engineer]

Usually through free radical addition.

 

 

GGG.bmp

Edited May 14, 2016 by Elite Engineer

[hypervalent_iodine]

Usually through free radical addition.

 

How exactly do you propose to do the reaction explicitly mentioned and asked about in the OP by radical addition?

 

OP: First thing: you haven't drawn a hexanone, you've drawn a heptanone. Which is correct? Could you also give more info on this question? Is there some restriction for what your starting materials can be? Are you actually planning on doing this? As to your specific reaction schemes: formation of the C-C bond isn't going to occur with the the two molecules you have there. Are you familiar with what an Aldol reaction is? This might be a better route.

[Sciencegeeknm]

Hi,

 

Sorry it is heptanone I have drawn. The target molecule is one I have just randomly drawn. I do not intend to make it.

 

I study organic chemistry as a hobby/interest and watch online lectures. The lectures are now covering synthesis so I have tried to do one myself. I learnt that the starting material should only be 4 or 5 carbons and possibly an alcohol? Im trying to do a retro synthesis here but probably not very well.

 

How would you go about making this target molecule? Or have I drawn something which can't be made?

 

Thanks

 

Nick.

[hypervalent_iodine]

Hi,

Sorry it is heptanone I have drawn. The target molecule is one I have just randomly drawn. I do not intend to make it.

I study organic chemistry as a hobby/interest and watch online lectures. The lectures are now covering synthesis so I have tried to do one myself. I learnt that the starting material should only be 4 or 5 carbons and possibly an alcohol? Im trying to do a retro synthesis here but probably not very well.

How would you go about making this target molecule? Or have I drawn something which can't be made?

Thanks

Nick.

Sorry to only now be replying to this. The compound can certainly be made, but not with the two compounds you have listed. I would go via the Aldol route I mentioned (using acetaldehyde and 2-pentanone), followed by substitution of the alcohol to get the bromo compound.

[Sciencegeeknm]

Thanks for your suggestion of using the Adol reaction. On the attached file I have drawn out the reaction which I think is correct?

 

You said to substitute the OH for Br. Would you use H-Br and would the reaction follow the Sn1 pathway with water as the leaving group?

 

Many thanks.

[hypervalent_iodine]

HBr is fine. It's at a secondary position, so in theory it might do either. You can promote one path over the other by altering conditions, but it doesn't matter so much. Your starting material is racemic anyway, so which one you promote won't change the outcome.

[BabcockHall]

PBr₃ is another way to convert an alcohol into a alkyl bromide.