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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: Humpo on August 16, 2012, 05:05:37 AM

Title: DDQ and hydrogen cyanide
Post by: Humpo on August 16, 2012, 05:05:37 AM

I saw a question regarding this from May, but no-one actually answered this part. The MSDS for DDQ states that it reacts with water to produce HCN. I have seen papers showing that the reaction product of DDQ + water is an ammonium salt of DDQ with one CN replaced by OH. However I have been unable to find any specific reference to the production of HCN, or a mechanism by which it occurs. Some procedures are anhydrous, many others use water without any mention of a problem.

If you're able to point me in the direction of something that gives a true reflection of the likelihood and risk of HCN production then it would be much appreciated. I need to be able to satisfy others that the way in which we want to use it is safe.

Many thanks.

Title: Re: DDQ and hydrogen cyanide
Post by: discodermolide on August 16, 2012, 05:08:33 AM

Quote from: Humpo on August 16, 2012, 05:05:37 AM

I saw a question regarding this from May, but no-one actually answered this part. The MSDS for DDQ states that it reacts with water to produce HCN. I have seen papers showing that the reaction product of DDQ + water is an ammonium salt of DDQ with one CN replaced by OH. However I have been unable to find any specific reference to the production of HCN, or a mechanism by which it occurs. Some procedures are anhydrous, many others use water without any mention of a problem.

If you're able to point me in the direction of something that gives a true reflection of the likelihood and risk of HCN production then it would be much appreciated. I need to be able to satisfy others that the way in which we want to use it is safe.

Many thanks.

I've used DDQ many times, aqueous and non-aqueous. I have never detected HCN being produced. Not to say it may not happen.
See http://chemjobber.blogspot.ch/2012/08/process-wednesday-20001st-time.html (http://chemjobber.blogspot.ch/2012/08/process-wednesday-20001st-time.html)
for what could happen.

Title: Re: DDQ and hydrogen cyanide
Post by: Humpo on August 16, 2012, 05:22:45 AM

Thanks for the quick reply.
I'm in the same situation. Never used it myself, but have plenty of colleagues with the "Used it many times and never seen a problem" type experience, but that won't be enough to satisfy the "What if..." raised by possibilities such as the link you gave.
Do you take any precautions against cyanide formation?
When you say that you've never observed it, have you actually attempted to detect it?

Thanks

Title: Re: DDQ and hydrogen cyanide
Post by: discodermolide on August 16, 2012, 05:57:23 AM

Quote from: Humpo on August 16, 2012, 05:22:45 AM

Thanks for the quick reply.
I'm in the same situation. Never used it myself, but have plenty of colleagues with the "Used it many times and never seen a problem" type experience, but that won't be enough to satisfy the "What if..." raised by possibilities such as the link you gave.
Do you take any precautions against cyanide formation?
When you say that you've never observed it, have you actually attempted to detect it?

Thanks

Yes we tried to detect it but never found anything. We attched a bleach scrubber to our reactions and reactors, just in case.

Title: Re: DDQ and hydrogen cyanide
Post by: zoork34 on August 20, 2012, 04:18:13 PM

Seems reasonable that it could happen.  If water attacks the ring and displaces one of the cyanide groups, you will have a protonated alcohol attached to the ring (pKa ~ -3) and a cyanide ion (pKa ~ 9) so the cyanide, in the absence of any other bases would seem likely to become protonated and form hydrogen cyanide.