4 transformation questions

[chemstudent5]

Hi all, I'm new here. I needed some help with my organic homework, and I stumbled across your forums. Here are my questions. I appreciate any help! Thanks!

 

a) propyne to 2-hexyne using propyne as the only carbon source

b) butane to (2E,5E)-2,5-heptadiene, again with propyne as the carbon source

c) propane to butanal (yes, that "a" is right. it's not butanol). Ethyne as an additional carbon source

d)propane to a racemic mixture containing (2R,3S)-hexanediol (propane is only carbon source)

[Darkblade48]

Have you tried working out any of these synthesis problems on your own yet? If so, please show us what effort you have tried putting into solving these questions

[chemstudent5]

I believe I have solved problem a. (see solution below)

 

Also on c, I have made some headway. I have found a mechanism to go from propane to butanal using CO. However, my carbon source must be ethyne. For b) and d) however I am at a complete loss as to how to proceed.

 

a) propyne + H2/lindlar catalyst ----> CH3CH=CH2

CH3CH=CH2 + Hg(OAc)2, H2O / NaBH4 ---> CH3CH2CH2OH

CH3CH2CH2OH +SOCl2 ---> CH3CH2CH2Cl

 

Separately,

 

propyne + LDA (lithium diisopropyl amide) ----> CH3CCLi

 

Now add the two together:

 

CH3CC- + CH3CH2CH2Cl ----> 2-hexyne (substitution rxn)

[chemstudent5]

Ok...in part a), I was wrong. Hydroboration instead of oxymercuration.

 

In part b) I have got all the way to heptane, but I'm not sure how to get to 2,5 heptadiene.

 

In part c) I have to add propane (3C's) with ethyne (2C's) and get butanal (4C's). I have no idea how to break the ethyne in half....or even if that's how to do it.

 

In part d) Propane + propane gives me hexane....but then I'm not sure how to go to an internal diol.