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Topic: Synthesize 2-butanol from ethane  (Read 10761 times)

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Offline sammyjo06

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Synthesize 2-butanol from ethane
« on: June 18, 2009, 04:12:14 PM »
I am supposed to synthesize 2-butanol from ethane using only ethane as my carbon source (can use any other inogranic/organic reagents/solvents).

I was thinking of doing ethylmagnesium bromide + acetaldehyde in diethyl ether and H3O+, but I need to figure out how to make those, first.

For ethylmagnesium bromide, can I just do CH3CH3 + Br + light --> CH3CH2Br, or can I not do that, because I don't know if that would work since the radical would be on a primary carbon?

If it worked, I would then add Mg.

To make the acetaldehyde, I would first make ethyl alcohol by doing CH3CH3 + Br + light --> CH3CH2Br and then add H2O to hopefully get CH3CH2OH and then I would do PCC to get CH3CH2O. Again, I don't know if this would work b/c of the primary radical and then primary carbocation for the addition of water.

Is any of this right, or am I completely on the wrong track?

Offline sjb

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Re: Synthesize 2-butanol from ethane
« Reply #1 on: June 18, 2009, 04:19:50 PM »
Sounds reasonably sensible to me - depending on what reactions you have covered I'd perhaps look at other oxidation methods for ethanol to acetaldehyde if I were to actually do this in the lab.

Oh, and be careful on your acetaldehyde formula!

Offline sammyjo06

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Re: Synthesize 2-butanol from ethane
« Reply #2 on: June 18, 2009, 04:44:15 PM »
Sounds reasonably sensible to me - depending on what reactions you have covered I'd perhaps look at other oxidation methods for ethanol to acetaldehyde if I were to actually do this in the lab.

Oh, and be careful on your acetaldehyde formula!

Thanks for the help :)!

This is just a homework assignment -- not doing it in the lab, so as long as it works on paper, I'm good lol :P.

Offline StarvinMarvin

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Re: Synthesize 2-butanol from ethane
« Reply #3 on: June 18, 2009, 05:31:17 PM »
If I may add, I'd find other oxidant - PCC is non-selective. Perhaps Swern oxidation would be better?

Offline macman104

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Re: Synthesize 2-butanol from ethane
« Reply #4 on: June 18, 2009, 05:49:27 PM »
If I may add, I'd find other oxidant - PCC is non-selective. Perhaps Swern oxidation would be better?
Why do you say PCC is non-selective?

Offline StarvinMarvin

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Re: Synthesize 2-butanol from ethane
« Reply #5 on: June 18, 2009, 06:12:42 PM »
because you can oxidize alcohol tyo acid just as well.

Offline macman104

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Re: Synthesize 2-butanol from ethane
« Reply #6 on: June 18, 2009, 06:25:31 PM »
because you can oxidize alcohol tyo acid just as well.
With PCC?  I thought the point is that without the water(which is in the Jones oxidation), you cannot form the hydrate of the aldehyde which then is capable of undergoing further oxidation.

Offline sammyjo06

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Re: Synthesize 2-butanol from ethane
« Reply #7 on: June 18, 2009, 10:20:03 PM »
because you can oxidize alcohol tyo acid just as well.
With PCC?  I thought the point is that without the water(which is in the Jones oxidation), you cannot form the hydrate of the aldehyde which then is capable of undergoing further oxidation.

I realize Wikipedia is a horrible source to cite, but they say the same thing lol:

Pyridinium chlorochromate is a reddish orange solid reagent used to oxidize primary alcohols to aldehydes and secondary alcohols to ketones. Pyridinium chlorochromate, or PCC, will not fully oxidize the alcohol to the carboxylic acid as does the Jones reagent.

Offline 408

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Re: Synthesize 2-butanol from ethane
« Reply #8 on: June 19, 2009, 01:06:55 AM »
When dry PCC will stop at aldehyde.
Addition of periodic acid or water will cause oxidation to acid.

Anyway, passing EtOH over a heated copper gauze  with O2 present is much sexier than PCC to get acetaldehyde.

Also adding water to EtBr is impractical on lab scale.  Go with a hydroxide (Na, K etc) and temp and solvent conditions to disfavor elimination

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