[the_negro_puppy]

What reagents are required, and in what order for this reaction?

Thanks very much for your input and *delete me*

[Donaldson Tan]

1-propyl-cyclohexane -> 1-cyclohexyl-prop-2-ene (dehydrogenation)

1-cyclohexyl-prop-2-ene -> required product (using a very weak oxiding agent, such as chromate(VI) in alkali)

[the_negro_puppy]

Thanks for the reply!

Would a reagent such as AlCl3 be approriate for dehydrogenation?
Or would FeCl3 be more appropriate?

Thanks

[swati]

1-cyclohexyl-prop-2-ene -> required product (using a very weak oxiding agent, such as chromate(VI) in alkali)

1-cyclohexyl-prop-2-ene -----> 1-cyclohexyl-propane-2,3-diol (using a very weak oxiding agent, such as chromate(VI) in alkali)

But the required product is 1-cyclohexyl-ethane-1,2-diol

[the_negro_puppy]

1-cyclohexyl-prop-2-ene -> required product (using a very weak oxiding agent, such as chromate(VI) in alkali)

1-cyclohexyl-prop-2-ene -----> 1-cyclohexyl-propane-2,3-diol (using a very weak oxiding agent, such as chromate(VI) in alkali)

But the required product is 1-cyclohexyl-ethane-1,2-diol

I dont understand, thats not what he said at all.

[Albert]

Yes, I'd say swati is right. the_negro_puppy, could you check whether or not you correctly copied the structures?

[wereworm73]

The product in your diagram is 1-cyclohexyl-ethane-1,2-diol.


 CH2--CH2     OH  OH
 /       \    |   |
CH2     CH----C---C-H
 \       /    |   |     
 CH2--CH2     H   H


If it was 1-cyclohexyl-propane-2,3-diol, then it would be this...



 CH2--CH2      H   OH  OH
 /       \     |   |   |
CH2     CH-----C---C---C-H
 \       /     |   |   | 
 CH2--CH2      H   H   H

[the_negro_puppy]

The product in your diagram is 1-cyclohexyl-ethane-1,2-diol.


 CH2--CH2     OH  OH
 /       \    |   |
CH2     CH----C---C-H
 \       /    |   |     
 CH2--CH2     H   H


If it was 1-cyclohexyl-propane-2,3-diol, then it would be this...



 CH2--CH2      H   OH  OH
 /       \     |   |   |
CH2     CH-----C---C---C-H
 \       /     |   |   | 
 CH2--CH2      H   H   H


Thanks for the input. The structures i drew are correct, but i cant see anywhere in this thread where anyone mentioned the name of the final product, so im not sure what your talking about.

The problems is completing that synthesis in 3 or less steps, that is:

1-propyl-cyclohexane -> 1-cyclohexyl-prop-2-ene (dehydrogenation) --------> 1-cyclohexyl-ethane-1,2-diol. (Using weak oxidising agent such as Cr(IV) in alkali.

My question is, what exact substances should i use for both the dehydrogenation and weak oxidation.

At the moment im thinking of AlCl3 or FeCl3 for dehydrogenation, and possibly PCC as the weak agent?

[Will]

Thanks for the input. The structures i drew are correct, but i cant see anywhere in this thread where anyone mentioned the name of the final product, so im not sure what your talking about.

The problems is completing that synthesis in 3 or less steps, that is:

1-propyl-cyclohexane -> 1-cyclohexyl-prop-2-ene (dehydrogenation) --------> 1-cyclohexyl-ethane-1,2-diol. (Using weak oxidising agent such as Cr(IV) in alkali.

I think after you get allylcyclohexane (1-cyclohexylprop-2-ene) you will need to do something like ozonolysis with a work-up with NaBH₄ to get MeOH and 2-cyclohexylethanol and then elimination (dehydration with H₂SO₄) to get vinylcyclohexane which you can oxidise with OsO₄ (or epoxidise with meta-chloroperoxybenzoic acid for example and then react with HO^-) to your diol (1-cyclohexylethane-1,2-diol).
Unfortunately that is (at least) four 'steps' . Somewhere in your synthesis you must remove a carbon atom from your propyl chain; I don't know what would be the best way of doing it, sorry!

Sorry to correct you but the suggested Chromate(VI) changed to Cr(IV)!

[the_negro_puppy]

Please help my exam is tomorrow

[Will]

Hi guys, its 12 hours to my final exam and i really need help with this question. I have posted this in a previous thread but forgot to add the Br!

I need to complete this synthesis using any reagents in 3 steps or less



Thanks very much for your help.

Hmm... that's ever so slightly easier!!
In fact you could probably use the information in the thread here to apply it to the correct question; all you needed to know is how to do the elimination step.

But...

 

1.)  1-bromo-2-cyclohexyl ethane -----------> 1-cyclohexyl ethene
       Dehydrohalogenation using NaOEt and EtOH

2.)  1-cyclohexyl ethene ---------------> 1-cyclohexyl ethane-1,2-diol
       Hydroxylation using following reagents
         (i) Cold aqueous alkaline KMnO4
                         OR
        (ii) OsO4 followed by hydrolysis

I think that the first step is not so great. Although NaOEt is fine if the primary bromide was more hindered, I just think it isn't hindered enough so you may get a S_N2 reaction instead, or both S_N2 and E2 reactions. Bases like DBN, DBU, KOCEt₃ and KOt-Bu would be better as they are hindered nucleophiles.

Also I would name the product of the first reaction vinylcyclohexane or at least cyclohexylethene; there is no need for the spaces between the cyclohexyl bit and the ethane/ethene bit.

(the_negro_puppy: please stick to one thread for one 'topic', and good luck in your exam! )

[swati]

Also I would name the product of the first reaction vinylcyclohexane or at least cyclohexylethene; there is no need for the spaces between the cyclohexyl bit and the ethane/ethene bit.

I agree with your statement & hence modified it as vinylcyclohexane 

I think that the first step is not so great. Although NaOEt is fine if the primary bromide was more hindered, I just think it isn't hindered enough so you may get a S_N2 reaction instead, or both S_N2 and E2 reactions. Bases like DBN, DBU, KOCEt₃ and KOt-Bu would be better as they are hindered nucleophiles.

Also changed the reagents of first reaction.