[AhmedEzatAlzawalaty]

why diazotisation rection needs to happen at 0 C very low temp.?

[Ψ×Ψ]

Just did one yesterday.  Can be crazy-exothermic. 

[movies]

Diazo compound + heat --> boom.

[Ψ×Ψ]

Fortunately, mine didn't explode.   

[charco]

Diazo compounds are very unstable and decompose as the temperature rises. The diazonium salt can be prepared at temperatures below 5ºC from a sodium nitrite and hydrochloric acid mixture acting on an amine and is stable enough to then be reacted with other species to form arene substitution products or diazo linked arenes. If the temperature is too high (above 10ºC ish) then the diazo compound does not form you merely get nitrogen liberated from the dilute nitrous acid/amine and an alcohol/phenol.


RNH2 + HNO2 --> ROH + H2O + N2

Nitrous acid itself decomposes/disproportionates at temperatures above 5ºC

2HNO2 --> H2O + NO + NO2

[ARGOS++]

Dear ALL,

That’s absolutely the WRONG  “Picture”  you draw,  ? ALL together!
(Sorry, I did only several times 10’000 Diazotisation, but a lot others, too!)

The Exothermic is NEVER the problem, but the human, because NOTHING is
such easy to overcome, as Exothermic:  With the patience!
       Drop the Speed and you will NEVER have any problem with Exothermic !!!
       [ I did Diazotisations by 80° Celsius (~ 175° Fahrenheit) !!! ]

So the right answer is:
     The high of the Activation-Energy (= Increasing Speed) of the FOLLOW-UP Reaction:
     The Destruction-Reaction of the ALL TIMES INSTABLE Diazo, you just formed!
           So, Lower the temperatur creats a higher HILL!

You may see:  It’s easy to climb EVERY hill of Activation with enough Speed!

P.S.:  Drop the Speed, Drop by Drop of the Regency.   
         Activation is not the only reason why doing it: Drop by Drop!

(Is it not exactly the same as on our streets?:
         Empower EVERY and EACH motor, and set Limits of Speed at the same time?)


Good Luck!
                 ARGOS⁺⁺

[madscientist]

Although your right, we all dont have a milllion years to wait for a reaction to complete.

[ARGOS++]

Dear madscientist,

Your absolutely RIGHT,   ?  But, You lost "The Picture"!

Remember:
  (Sorry, I did only several times 10’000 Diazotisation, but a lot others, too!)

Good Luck!
                 ARGOS⁺⁺