Sciencemadness Discussion Board

Diazotization safety

maxpayne - 21-3-2013 at 09:27

When an amine reacts with nitrous acid and HX in aq. solution, diazonium compound is formed. If temperature is higher than 5°C, this compund is unstable and N2 gas is formed, and halogen replaces the amine group.

Why this process do not cause dramatic energy release as is when diazonium compound is isolated as crystals and detonated?

Nicodem - 21-3-2013 at 10:26

Quote: Originally posted by maxpayne  
If temperature is higher than 5°C, this compund is unstable and N2 gas is formed, and halogen replaces the amine group.

Where did you get that from? There is no such rule of the 5 °C. Diazonium compounds can either decompose immediately upon formation, deprotonate to diazo compounds, or form isolable and stable salts at room temperature or higher. It all depends on their structure.
Quote:
Why this process do not cause dramatic energy release as is when diazonium compound is isolated as crystals and detonated?

Obviously a reaction, even if highly exothermic, can never be as dramatic as a detonation. Reaction kinetics and shock waves make a world of a difference.

DraconicAcid - 21-3-2013 at 10:40

Quote:
Quote: Originally posted by Nicodem  
Quote: Originally posted by maxpayne  
Why this process do not cause dramatic energy release as is when diazonium compound is isolated as crystals and detonated?

Obviously a reaction, even if highly exothermic, can never be as dramatic as a detonation. Reaction kinetics and shock waves make a world of a difference.


An exothermic reaction in solution has the solvent to absorb most of the heat generated. The heat given off by the decomposition of a substance in a crystal is transferred only to the parts of the crystal surrounding the bit that gave it off, which heats those parts up dramatically and causing them to decompose as well. Then they give off heat, destroying their neighbors, and so on, and so on.

maxpayne - 21-3-2013 at 10:52

Quote: Originally posted by Nicodem  
Quote: Originally posted by maxpayne  
If temperature is higher than 5°C, this compund is unstable and N2 gas is formed, and halogen replaces the amine group.

Where did you get that from? There is no such rule of the 5 °C. Diazonium compounds can either decompose immediately upon formation, deprotonate to diazo compounds, or form isolable and stable salts at room temperature or higher. It all depends on their structure.
Quote:
Why this process do not cause dramatic energy release as is when diazonium compound is isolated as crystals and detonated?

Obviously a reaction, even if highly exothermic, can never be as dramatic as a detonation. Reaction kinetics and shock waves make a world of a difference.


I get it from Wikipedia : Diazonium_compound
"In aqueous solution diazonium salts are unstable at temperatures above +5 °C; the -N+≡N group tends to be lost as N2 (nitrogen gas)."

So, this is not a general rule?

maxpayne - 21-3-2013 at 10:55

Quote:
Quote: Originally posted by DraconicAcid  
Quote: Originally posted by Nicodem  
Quote: Originally posted by maxpayne  
Why this process do not cause dramatic energy release as is when diazonium compound is isolated as crystals and detonated?

Obviously a reaction, even if highly exothermic, can never be as dramatic as a detonation. Reaction kinetics and shock waves make a world of a difference.


An exothermic reaction in solution has the solvent to absorb most of the heat generated. The heat given off by the decomposition of a substance in a crystal is transferred only to the parts of the crystal surrounding the bit that gave it off, which heats those parts up dramatically and causing them to decompose as well. Then they give off heat, destroying their neighbors, and so on, and so on.


I did not expect such beautiful explanation! Thanks!!

DraconicAcid - 21-3-2013 at 10:56

Quote: Originally posted by maxpayne  


I get it from Wikipedia : Diazonium_compound
"In aqueous solution diazonium salts are unstable at temperatures above +5 °C; the -N+≡N group tends to be lost as N2 (nitrogen gas)."

So, this is not a general rule?

*Very* general. Some are more stable than others, and they can decompose by different pathways.