Sciencemadness Discussion Board

formic acid from ethyl formate

bromosapien - 26-6-2024 at 01:08

I have some ethyl formate and I'd like to make some formic acid from it.

I understand that ethyl formate is made by 'esterification' of ethanol and formic acid. How can I reverse this process?

Sorry if this is spoon-feedy, but I haven't found a satisfactory reference for such a 'de-esterification.' From what I understand, it would be accomplished with heat and strong acid, but the reaction is an equilibrium... can I distill off the ethanol as it is formed, and would that force the reaction in one direction?

I'm more interested in learning the chemistry than simply obtaining the formic acid, so feel free to simply post links to your most useful references for this and maybe a hint or two, and I'll dive in. Thanks in advance

[Edited on 26-6-2024 by bromosapien]

EF2000 - 26-6-2024 at 02:27

The reaction you planning to do is called acidic hydrolysis. As it is the direct opposite of acid-catalyzed esterification, you need reverse conditions: a bit of acid and a lot of water.

You can also try alkaline hydrolysis, it is not equilibrium reaction and goes to completion. You will get ethanol and formate salt. Then formic acid is easily displaced with any reasonably strong acid.
An example of alkaline hydrolysis can be found in Laboratory manual of organic chemistry by H. Fisher: Experiment No. 25
Note: if you choose alkaline hydrolysis, don't use concentrated sulfuric acid to displace formic acid from formate: it has unpleasant tendency to dehydrate formic acid, producing carbon monoxide.

Since the goal is learning, you can try both ways and compare results.


[Edited on 26-6-2024 by EF2000]

Precipitates - 26-6-2024 at 05:32

Ethyl formate has a lower boiling point so you will likely distill this off before ethanol, and then you'll push the equilibrium the other way.

An easier way is probably the alkaline hydrolysis as mentioned by EF2000.

I quite like the LibreTexts chemistry pages:
Hydrolysis of esters

I use them to refresh my basic chemistry knowledge!

[Edited on 26-6-2024 by Precipitates]

bromosapien - 26-6-2024 at 14:24

Thank you guys! I will have a go at the base catalyzed reaction to sodium formate.

Then, to liberate formic acid with a stronger acid, if sulfuric is out of the question, what options are there for getting close to pure formic? using a concentrated aqueous strong acid such as hcl would result in aqueous formic of comparable concentration, no? can one use an anhydrous solution of hcl in some solvent that can be distilled off? or hcl gas?

bnull - 26-6-2024 at 16:46

Quote: Originally posted by bromosapien  
Then, to liberate formic acid with a stronger acid, if sulfuric is out of the question, what options are there for getting close to pure formic? using a concentrated aqueous strong acid such as hcl would result in aqueous formic of comparable concentration, no? can one use an anhydrous solution of hcl in some solvent that can be distilled off? or hcl gas?

HCl would do, or phosphoric acid, or any soluble bisulfate (sodium, potassium, maybe ammonium). I suppose that even boric acid could work, since it does with sodium acetate. Perhaps even citric acid. In any case, you'll have to distill the acid from the solution. Distillation affords a solution of ~77% formic acid.

Precipitates - 26-6-2024 at 23:56

One thing that may be worth trying is a potential distillation free route as follows using iron (or copper) (1):

sodium formate + iron chloride -> iron formate + sodium chloride

Iron formate has low solubility so can be filtered off (in theory).

Then you can take an iron formate solution and add it to an oxalic acid solution, which may give formic acid similarly to sulphuric acid as discussed recently in another post (2):

iron formate + oxalic acid -> iron oxalate + formic acid

Note that this formic acid solution will be dilute, and contaminated with a small amount of iron and oxalate ions.

Will it work? Not sure, but it would certainly be an interesting way of learning the chemistry of displacement reactions.

1. Note this is all just speculation - I haven't tried this.
2. Notes on the new NurdRage video: making sulphuric acid from sulphates and oxalic acid