pKa of azide

JChem 5.10 reports the basic pK_a of [N-]=[N+]=[N-] to be 19.8.  The correct value is 4.7.

JChem 5.10 reports the basic pK_a of [N--][N+]#N to be 17.8.  Because this compound is identical to the previous one, its pK_a should also be 4.7.  There is no reason why these two resonance structures of the same compound should give different pK_a values.

Hi, when will this bug be fixed?

Hi,

The fix will be available in the 5.11 version in September.

Jozsi

Here are some related errors.

For hydrazoic acid N=[N+]=[N-], JChem reports a basic pKa of 17.8 for N1.  N1 is an acidic atom with an acidic pKa of 4.7.  I don't know what its basic pKa is, but it is very low.  

Likewise, for methyl azide CN=[N+]=[N-], JChem reports a basic pKa of 19.2 for N2.  I don't know what its basic pKa is, but it is very low. 

Hi,

Yes , there are problems.

 I read that the "N=[N+]=[N-]"  is protonable in super acids.  Its basic pKa is about -10. (I guess) 

the "CN=[N+]=[N-]" is "more" basic its pKa is about  -6.0. (just a guess)

Plotting of the "pH - species %" also incorrrect  in Marvin. 

Jozsi 

Jozsi wrote:

Hi, Yes , there are problems.  I read that the "N=[N+]=[N-]"  is protonable in super acids.  Its basic pKa is about -10. (I guess)  the "CN=[N+]=[N-]" is "more" basic its pKa is about  -6.0. (just a guess) Plotting of the "pH - species %" also incorrrect  in Marvin.  Jozsi

I'm not too concerned about the accuracy of the very negative pK_b values, as long as they are in the ballpark, not around 17-19.  I'm also very concerned that no acidic pK_a value is given for HN₃.  

These bugs appear to be fixed by JChem 5.11.5.  Thanks.