Sciencemadness Discussion Board

Acyl chlorides stability

outer_limits - 26-10-2020 at 11:25

How stable are acyl chlorides (acetyl, propionyl) in long term storage?

I know that they must be protected from any moisture because they will hydrolise giving carboxylic acid and HCl, but is there any risk of phosgene formation?

Is it better to convert them to anhydrides for long-term storage?

[Edited on 26-10-2020 by outer_limits]

clearly_not_atara - 26-10-2020 at 15:57

I see no reasonable formation pathway for phosgene from acetyl chloride.

A tiny amount of ketene ought to exist in equilibrium with acetyl chloride but does not accumulate unless there is a base and absolutely no water present, which is unlikely. Same for propionyl chloride with methylketene. This shouldn't be a risk unless you do something absolutely silly like storing your acetyl chloride over sodium sulfate (even then I doubt it).

Cou - 26-10-2020 at 17:27

I store several acid chlorides long term. They didn't even require hazmat shipping to buy. For my purpose it doesn't matter if some decomposition to carboxylic acid happens, because I use them to make esters. Any carboxylic acid contamination could be removed by acid washes of the final product of whatever reaction you use the acid clhorides for.

But I dunno how important it is to only open the bottles in a glovebox. A tiny amount of conversion of acid chloride to carboxylic acid might happen every time you open the bottle outside a glovebox, due to a very short exposure to water vapor in the air. I have a bottle of butyraldehyde that slightly smells of butyric acid due to opening it in air.

Anhydrides also react with water vapor so I don't think it would make a difference.

[Edited on 10-27-2020 by Cou]

Cou - 27-10-2020 at 21:12

*base washes

FrenchChemist - 14-4-2021 at 20:49

If you have purchased chlorides, the original packaging will suffice and the substance will not become anything for years.
If you received it yourself, of course, distillation is the minimum, plus a suitable bottle with a PTFE stopper. Some people flush the bottles with nitrogen to extend the shelf life, this is an option only for those who have an inert gas on the "occasion" when working with, for example, grignard, otherwise it is not worth investing in this way of packaging and storage.

Oxy - 29-4-2021 at 00:17

I keep mine in the condition which are far from ideal and they are pretty stable. Original bottle and ziplock do the trick and keep the humidity away.

woelen - 29-4-2021 at 04:24

Quote: Originally posted by Cou  
But I dunno how important it is to only open the bottles in a glovebox. A tiny amount of conversion of acid chloride to carboxylic acid might happen every time you open the bottle outside a glovebox, due to a very short exposure to water vapor in the air. I have a bottle of butyraldehyde that slightly smells of butyric acid due to opening it in air.
For this reason, I take small working quantities from my stock bottles and only open the stock bottles if the working quantity is used up. I have 1 liter of acetyl chloride. I put 60 ml in a separate small bottle and use that for experiments, mostly at test tube scale. Using this strategy, only the 60 ml bottle is opened frequently, the stock bottle remains good and pure.

I use this strategy for all chemicals, which are moisture sensitive, are easily oxidized, discolor when absorbing air, are very hygroscopic, etc.

FrenchChemist - 29-4-2021 at 05:27

Quote: Originally posted by woelen  
For this reason, I take small working quantities from my stock bottles and only open the stock bottles if the working quantity is used up. I have 1 liter of acetyl chloride. I put 60 ml in a separate small bottle and use that for experiments, mostly at test tube scale. Using this strategy, only the 60 ml bottle is opened frequently, the stock bottle remains good and pure.

I use this strategy for all chemicals, which are moisture sensitive, are easily oxidized, discolor when absorbing air, are very hygroscopic, etc.


Good way woelen, or as I asked Mario for a bottle of AcroSeal when I bought products from him, so I can use my chloride with virtually no "contact" with a needle and syringe and the reagent is still under nitrogen.

Of course, not all substances require such precautions, but I appreciate the quality of the reagent and I prefer some of them to be in good condition for the longest time