None of the places I supply offer propionaldehyde. Does anybody have a reference to a doable preparation method. All I could find were catalytic,
vapor phase, industrial processes using allyl alcohol as the starting material. High temperatures and pressure are required and I'm looking for
something I could do using just my glassware.woelen - 6-9-2013 at 01:05
Oxidation of 1-propanol with acidified dichromate in aqueous solution seems easiest to me. Just assure that you never have excess dichromate in the
solution, because that will lead to further oxidation to propionic acid. I would prepare a solution of 1-propanol in dilute H2SO4 (e.g. 10%) and then
drop in (while stirring) the solution of K2Cr2O7 or Na2Cr2O7. Try to use so much dichromate that there is just enough for the oxidation of all of the
1-propanol. Assure that there is an excess amount of acid.
Isolation of the propionaldehyde should not be that difficult. Its boiling point is much lower than that of water, 1-propanol and propionic acid. If
it forms azeotropes, then things may be more difficult, I'm not sure about that. I would first try on a small scale.DJF90 - 6-9-2013 at 01:30
Ideally you would add 1-propanol to a hot solution of acidified dichromate, such that the aldehyde distills as it is formed.
It depends on the scale you want to work on, your capabilities, and your resources. For small scale, chromium VI isn't too bad, and selective
conditions for the aldehyde can be used (e.g. PCC in DCM). On a larger scale, the chromium wastes become troublesome/excessive and it's better to use
another method. Given the relatively low cost of the starting alcohol, it probably doesn't warrant the use of expensive reagents like oxalyl chloride
(Swern) or TPAP (even in catalytic amounts). If you're after a fair quantity of the propionaldehyde, perhaps an approach using catalytic
TEMPO/KBr/NaOCl/DCM would be fairly cheap and selective.bobm4360 - 6-9-2013 at 10:19
If you can get the electrolysis method referenced in that OrgSyn paper - namely Reitlinger, Z. Elektrochem. 20, 261 (1914); Feyer, ibid. 25,
142 (1919) - to work, it would be ideal for the amateur experimenter. No need for carcinogenic oxidizers, just calcium chloride or dilute sulfuric
acid and propyl alcohol, plus the electrolytic cell, which can be used for lots of things. Anybody try this method?Magpie - 6-9-2013 at 15:16
Unitized Experiments in Organic Chemistry, 4th ed by Brewster et al has a preparation for propionaldehyde. It specifies a sodium
dichromate/H2SO4 solution added slowly to to the hot alcohol. A 3-neck RBF is used as pot connected to a condenser via a Claisen adapter so that the
aldehyde is immediately removed to prevent further oxidation. This is likely a version of the Org Syn procedure, simplified for student use.
Brewster's 1st edition has a similar procedure for making butyraldehyde from 1-butanol. I have tried this procedure quite a few times with only
limited success.
Making propionaldehyde with propylene glycol looks intriguing as I could use my tube furnace for that. The glycol should be OTC as RV anti-freeze.
[Edited on 6-9-2013 by Magpie]phendrol - 11-9-2013 at 13:58
Heating calcium formate and calcium propionate also seems easy and straightforward. Does anyone have some more info on this? I know that more
aldehydes and ketones can be produced using dry distillations. Anyone has some info or experience with this matter?Maximus - 13-9-2013 at 08:32
What about dry distillation of Propylene glycol with KHSO4/NaHSO4, like the dry distillation of glycerol with KHSO4 to obtain acrolein (After a
Pinacol Rearrangement and dehidration)Nicodem - 13-9-2013 at 08:55
Heating calcium formate and calcium propionate also seems easy and straightforward. Does anyone have some more info on this? I know that more
aldehydes and ketones can be produced using dry distillations. Anyone has some info or experience with this matter?
There is a reference for that in the Organic Syntheses article: Linneman, Ann. 161 (1872) 18-25, DOI: 10.1002/jlac.18721610104
What about dry distillation of Propylene glycol with KHSO4/NaHSO4, like the dry distillation of glycerol with KHSO4 to obtain acrolein (After a
Pinacol Rearrangement and dehidration)
It is not called dry distillation, if you are distilling a liquid from a liquid. Anyhow, you need an acid catalyzed vapor phase rearrangement for such
glycols in order to obtain the corresponding aldehydes. Enolizable aldehydes are not stable enough toward acids in the liquid phase. The rearrangement
of propylene oxide over silica gel in the vapor phase at 300 °C is described in the patent cited in the Org. Synth. article. Often, the same
conditions work for glycols as well, as the reaction mechanism is similar. Particularly since another example in that review is the rearrangement of
propylene glycol to propionaldehyde at 500 °C, apparently uncatalyzed (DOI: 10.1002/jlac.19043350108).Maximus - 14-9-2013 at 00:53
