It is most likely benzoic acid or perbenzoic acid. Oxidation of benzaldehydes that have been freshly distilled and hence are free of inhibitors is extremely fast. I have seen crystals at the end of a 3-hour undergrad. lab in a bottle that was fresh at the beginning.
If it forms a peroxide, then this would almost certainly not occur at the aromatic ring, but by removal of H radical from the aldehyde. This yields PhC=O radical and HOO radical, which would re-combine to form the peracid. PhC=O also likely undergoes loss of carbon monoxide, giving Ph radical that would end up as phenyl peroxide. The peroxy compounds would likely also photo-dissociate into carboxy radicals and alkoxy radicals, and so on. I would also speculate that one molecule of per-acid oxidizes another of aldehyde, thereby giving two benzoic acids. So overall it is unlikely that much peracid would build up.
The other key safety point is that aryl per-acids such as per-benzoic acid or meta-chloro derivative, mCPBA, are much more stable than alkyl peroxides such as those from ether. They likely can be handled by cautious addition of a reducing agent. Try iodide, and watch the iodine form!
If the bottle is large, however, or if you are not a chemist by training, I would urge more caution.
On Tue, 18 Feb 2014 23:59:19 +0000 Paul Harrison If you have an accommodation need for a planned meeting, please e-mail me directly and I will do my best to make appropriate arrangements. Should you require any materials sent via this e-mail address in an alternate/accessible format, please let me know Previous post | Top of Page | Next post
> I just did a lab safety inspection and found a bottle of Benzaldehyde with crystal formation. The bottle is dated back to 5-25-1989. I am not sure if this is peroxide or just polymer being formed. What are your thoughts? If it is peroxide, what is the proper protocol for handling it?
Associate Professor of Chemistry
Department of Chemistry and Chemical Biology
1280 Main St. W., Hamilton, ON, L8S 4M1, Canada
Phone: (905)525-9140 ext. 27290; FAX: (905)522-2509
If you have an accommodation need for a planned meeting, please e-mail me directly and I will do my best to make appropriate arrangements. Should you require any materials sent via this e-mail address in an alternate/accessible format, please let me know
Previous post | Top of Page | Next post