Ethanol Acidity: Does It Gain or Lose a Proton?

[alingy1]

Is ethanol basic or acidic?
It has an -OH group... but that does not necessarily mean basicity. How does ethanol react in water? Does it gain a proton, does it lose one, or does it lose the hydroxyde...?

 

[SteamKing]

The presence of the OH in ethanol is an accident of its composition. Ethanol in water does not dissociate like NaOH, for instance. It is essentially neutral on the acid-base scale, or pH = 7.00. Organic molecules are not ionically bonded, like HCl or NaOH.

http://en.wikipedia.org/wiki/Ethanol

 

[alingy1]

Ethanol is supposedly basic. But why? What do you mean by accident?

 

[SteamKing]

Ethanol is supposedly basic.

I'd like to see a reference for that statement.

But why? What do you mean by accident?

All alcohols have at least one OH group attached to a carbon atom, but that fact by itself does not necessarily mean that alcohols are bases. The behavior of alcohol molecules is more complex than one finds with simple acids and bases, like HCl and NaOH.

It's like saying, 'All cows have four legs. A horse has four legs. Therefore, a horse is also a cow."

Certain alcohols besides ethanol can be acidic. Alcohols can react with both acids and bases. Ethanol is just one type of alcohol, which constitute a rather large group of organic compounds. Some of the characteristics of alcohols as a group are discussed here:

http://en.wikipedia.org/wiki/Alcohol

Other organic compounds besides alcohols also contain an OH group, but these compounds are acidic. A simple example is acetic acid, CH3COOH:

http://en.wikipedia.org/wiki/Acetic_acid

 

[hilbert2]

If reacted with sufficiently strong acid or base, an ethanol molecule can either lose or gain a proton, forming an ethoxide ion ##CH_3CH_2O^-## or an ethyloxonium ion ##CH_3CH_2OH_2^+##. However, acids or bases strong enough to cause these reactions can't exist in water solutions.

 

[epenguin]

If reacted with sufficiently strong acid or base, an ethanol molecule can either lose or gain a proton, forming an ethoxide ion ##CH_3CH_2O^-## or an ethyloxonium ion ##CH_3CH_2OH_2^+##. However, acids or bases strong enough to cause these reactions can't exist in water solutions.

Well ethanol has a pK near 16 implying that in IM NaOH a respectable 1% of it would be the ethanolate cation EtO^- , several times more with methanol. At lower pH's even if the amount is tiny, it can be highly significant in reaction mechanisms and kinetics if these are the reactive species

 

[SteamKing]

How does ethanol react in water? Does it gain a proton, does it lose one, or does it lose the hydroxyde...?

It doesn't for the most part. Although some prefer to use a spritz of soda water as their mixer.