Reversing oxidation of ethyl alcohol

[Ethereally Luminous]

Hi I am new to this forum, so this will be my first post. I am curious to know if there is any way to reverse the oxidation reaction of ethyl alcohol in to acetic acid.

Edited December 3, 2010 by Ethereally Luminous

[mississippichem]

Hi I am new to this forum, so this will be my first post. I am curious to know if there is any way to reverse the oxidation reaction of ethyl alcohol in to acetic acid.

 

[ce]LiAlH_{4}[/ce] ("lithium aluminum hydride") will reduce acetic acid back to ethanol. [ce]NaBH_{4}[/ce] ("sodium borohydride") will reduce the acetic acid but will stop at acetaldehyde. Both reagents are very water sensitive and are usually used as solutions in ether.

[Ethereally Luminous]

[ce]LiAlH_{4}[/ce] ("lithium aluminum hydride") will reduce acetic acid back to ethanol. [ce]NaBH_{4}[/ce] ("sodium borohydride") will reduce the acetic acid but will stop at acetaldehyde. Both reagents are very water sensitive and are usually used as solutions in ether.

 

Thanks for the information. So rather than just mixing LiAlH4 with acetic acid, mix the acetic acid with a solution of ether and LiAlH4.

[mississippichem]

Yep, might want to add dropwise. If there is any water in your solution you will find out quickly...the reaction of [ce] LiAl_4 [/ce] and water has some serious kick to it. Be careful.

[Horza2002]

Why do you think borohydride will stop at the aldehyde? Borohydride is usually used to reduce a aldeyde or ketone in the presence of other groups (e.g. esters). If you manage to reduce the carboxylic acid with borohydride, then you most certainly will reduce the aldehyde down to the alcohol (aldehydes are extremely reactive).

 

O and yes, if you going to use aluminium hydride, then make sure there is NO water ANYWHERE!

[mississippichem]

Why do you think borohydride will stop at the aldehyde? Borohydride is usually used to reduce a aldeyde or ketone in the presence of other groups (e.g. esters). If you manage to reduce the carboxylic acid with borohydride, then you most certainly will reduce the aldehyde down to the alcohol (aldehydes are extremely reactive).

 

O and yes, if you going to use aluminium hydride, then make sure there is NO water ANYWHERE!

 

Oh, sorry, good catch Horza. Should've said that borohydride will reduce aldehydes or ketones to the corresponding alcohol, but won't reduce the carboxylic acid.

[Horza2002]

Borane (BH3) is one reagent that will reduce a carboxylic acid to the corrosponding alcohol. I've never had much luck doing it, but according to the literature, it can be done

[mississippichem]

Interesting, never heard of that reaction before. Do you know if [ce]BH_{2}^{+}[/ce] is part of the intermediate?

[Horza2002]

Ive attached the mechanism for borane reduction. It works best for electron rich substrates because of the electron-deficient boron atom in the reagent. Amides are easily reduced with this method...esters are slower...carboxlylic acids are a little tricky but it works ok. I've managed to get around 55% yields doing reductions like this; not great but good. Depending on your molecule, its often easier to make the methyl ester and then use LiAlH4 to reduce the ester instead...but like i said it depends on the other groups present in your molecule.

borane.pdf

[Ethereally Luminous]

Interesting