# Creating ethane through electrolysis of vinegar

Some sources that I studied say that it is possible to produce ethane through the electrolysis of ethanoic acid. Would this work with vinegar (5-10% acid)? Also, other sources say that ethanoate salts should be used. I can easily obtain such salts (sodium hydrogen carbonate (baking soda) + ethanoic acid (vinegar)), and vinegar as well, so which one is better for creating ethane? I don't care about the amount of carbon dioxide, oxygen, hydrogen or any other gas produced.

## 2 Answers

Ethane is formed at the anode through $\ce{CH3COO- -> CH3. + CO2}$ and then $\ce{2 CH3. -> C2H6}$.

Since acetate solutions have a higher concentration of acetate anions than acetic acid I would use an acetate solution to get a higher concentration of acetate at the anode in favor of the formation of ethane.

Indeed that is quite possible. The reaction was first described by Hermann Kolbe and is hence called "Kolbe's Electrolysis"

It is a decarboxylative dimerisation of two carboxylate ions (carboxylate salts--either sodium, or potassium are used instead of carboxylic acids for precisely this reason as they disassociate more readily to furnish carboxylate ions).

The general reaction scheme is is a two-stage radical process: first, electrochemical decarboxylation gives a radical intermediate; then two such intermediates combine to form a covalent bond.

For sodium acetate (again would furnish acetate ions more readily than acetic acid) one would see the following reaction:

$\ce{2CH_3COO^-}\ce{Na^+} \rightleftharpoons \ce{2CH_3COO^-}+ \ce{Na^+}$

At the anode: a) $\ce{2CH_3COO^-} \stackrel{-2e-}\rightarrow \ce{2CH_3COO.}$

Electrons shuffle around a bit in the acetate radical and we get

b)$\ce{2CH_3COO.} \rightarrow \ce{2CH_3.} + \ce{CO_2}$

c)$\ce{2CH_3.} \rightarrow \ce{CH_3CH_3}$

At the cathode: a) $\ce{H_2O} + \ce{e-}\rightarrow \ce{OH^-} + \ce{H.}$

and, finally $2\ce{H.} \rightarrow \ce{H_2}$

Now, here we observe that the solution is becomes more basic as the reaction proceeds since hydroxide ions are being produced. If we make the conditions mildly acidic, and draw on Le Chatelier's principle, we can shift the reaction to the right.

So, it would make sense to use sodium acetate, in the presence of ethanoic acid to perform this reaction.

• So essentially if I were to do this entirely at home, I could neutralise some baking soda with excess of vinegar, and then electrolyse using carbon electrodes, collect all gas, and burn? (CO2 may be a problem though.) – sadljkfhalskdjfh Mar 20 '16 at 15:32
• Not neutralise. What I meant was simply try electrolysing a slightly acidified sodium acetate solution. I've never performed this synthesis myself so I can't be sure; If you try it out, let me know how it goes. – getafix Mar 20 '16 at 15:39
• However, I would produce the sodium acetate using neutralisation of baking soda and vinegar, so it would work...? Ethanoic acid == acetic acid. – sadljkfhalskdjfh Mar 20 '16 at 15:40
• Ah yes, indeed. sorry i misinterpreted what you just said. – getafix Mar 20 '16 at 15:41