Sciencemadness Discussion Board

Acetic anhydride storage and degrading

Hephestus - 6-8-2019 at 00:58

Hello to all people
I've had an issue recently with some acetic anhydride degrading in quality to where it's properties are similar to CH3COOH This is been perplexing as to my storing it.

The acetic anhydride was keep it in glass amber bottle which were then in a dark and cool cupboard. This is the last bits of a batch I got maybe a year ago at the longest time ago. I'm very careful with it. Yet, this has happened.

I've had a process I've had different results and after much checking of every aspect, I've narrowed it to the anhydride. I obtained a small amount of a different batch and this problem didn't occur.

Any input would be welcoming

NZniceguy - 6-8-2019 at 04:30

That is odd, ive kept it for months and had no issues but if its just a wee bit left in a big bottle and you live in a fairly humid area, the water content in the air space in the bottle could perhaps be the cause?
Send some to me and i'll check it for you. ;)

DavidJR - 6-8-2019 at 11:27

Maybe the cap wasn't sealing properly to prevent moisture ingress?

Ubya - 6-8-2019 at 12:56

Quote: Originally posted by DavidJR
|| Maybe the cap wasn't sealing properly to prevent moisture ingress?

most plausible reason, acetic anhydride doesn't go "bad" by itself

ZetekitoxinAB - 6-8-2019 at 15:38

Clean, water free acetic acid anhydride is stable indefinitely if protected from air. In what ways it has properties similar to acetic acid?

markx - 13-8-2019 at 02:33 far as my experience goes, if one does not deliberately pour water into the container then it shall not "go bad". I had remnants of an ancient batch in a huge loosely sealed glass bottle. It was stored in a shed for about a year in this condition (and only the Creator knows for how many decades before my time). No problems at all.
Another small quantity was from the 50s of last original bottle. Again stored in unknown conditions and not tightly sealed, remains very functional to this day.