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Author: Subject: Explosive cyanides
Whathappensif
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[*] posted on 30-7-2020 at 00:15
Explosive cyanides


I came across this description of Pb(CN)2 and apparently the compound is capable of exploding.

https://pubchem.ncbi.nlm.nih.gov/compound/Lead-cyanide#secti...

Quote:

LEAD CYANIDE is decomposed by acids to give off hydrogen cyanide, a flammable poisonous gas. Tends to explosive instability. Capable of violent oxidation: fusion with metal chlorates, perchlorates, nitrates or nitrites can cause explosions [Bretherick, 1979 p. 101]. Reacts with incandescence with magnesium [Mellor, 1940, Vol. 4, 271].


Checking Bretherick Vol 8, page 1282 says:
Quote:

Several members of this (often endothermic) group of com-
pounds which contain heavy metals tend to explosive insta-
bility, and most are capable of violent oxidation under
appropriate circumstances.


Incidentally lead thiocyanate is also described in the book as being explosive.

A redox reaction with oxidizing agents I can believe would cause an explosion, but can cyanides on their own explode? What happens if you have a large volume of lead cyanide or other powder, and then expose it to a shock from a detonator?
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aromaticfanatic
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[*] posted on 23-8-2020 at 03:39


I think the explosive power behind heavy metal salts is typically due to their weaker ionic bonding due to the sheer size of the atoms making the attraction between the nucleus and electrons a lot weaker. If two more stable products can be formed quickly enough, then you have a possible explosive. Since I'd assume metallic lead and HCN are both more stable than Pb(CN)2, I think it's possible. I wouldn't think it is very powerful though. It's like silver acetylide (not the double salt), it's pure bonds breaking and reforming that releases energy. If the cyanides can explode, then it'd be the same concept.

Explosives are commonly set off using detonators since the shockwave shifts the atoms in the molecules far enough for them to react. So in the case of classic TNT, the nitro groups get smushed hard enough to have the oxygen react with carbon and hydrogen. If the bond between Pb and CN is weak enough, and the energy released when that bond is broken and reformed, is powerful enough to trigger the next cycle of bond breaking and forming, you should have an explosive. Not a very good one since there is no oxidizing happening and the moles of gas made is very small compared to something like TNT, but explosive nonetheless.
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[*] posted on 23-8-2020 at 03:53


No heavy metal is required.
https://www.icheme.org/media/8681/paper-52-hazards-25.pdf
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