energyE() of diazonium ions

User 870ab5b546

11-04-2011 17:31:18


bob@epoch-virtual:web$ evaluate -e "energyE()" "N#[N+]c1ccccc1" -p 4
bob@epoch-virtual:web$ evaluate -e "energyE()" "[O-][N+](=O)c1ccccc1" -p 4
bob@epoch-virtual:web$ evaluate -e "energyE()" "Clc1ccccc1" -p 4

I don't know what the right localization energies of diazonium ions are, but it seems to me that the values should be considerably larger than JChem gives -- certainly they should be closer to chlorobenzene than they are now.

-- Bob

User 851ac690a0

18-04-2011 17:47:10


The "energyE" will be deprecated in the next version since the "energy" function is badly described in the  user's documentation and in fact it is weakly related with the so called Huckel localization energy. 

You can select from the "true  Huckel" parameters which are listed at this site:

Please try the next Huckel Function for calculating the localization energy with JChem.



User 870ab5b546

19-04-2011 18:20:35


bob@epoch-virtual:synthesis$ evaluate -e "hmoElectrophilicLocalizationEnergy()" "c1ccccc1F" -p 4
bob@epoch-virtual:synthesis$ evaluate -e "hmoElectrophilicLocalizationEnergy()" "c1ccccc1Cl" -p 4
bob@epoch-virtual:synthesis$ evaluate -e "hmoElectrophilicLocalizationEnergy()" "c1ccccc1Br" -p 4
bob@epoch-virtual:synthesis$ evaluate -e "hmoElectrophilicLocalizationEnergy()" "c1ccccc1I" -p 4

Looks like there are no parameters for Br or I.    It's useless to me without them.

I note that toluene and trifluorotoluene give the same result as bromobenzene, which makes this value not useful for calculating results of electrophilic aromatic substitution reactions.

bob@epoch-virtual:synthesis$ evaluate -e "hmoElectrophilicLocalizationEnergy()" "c1ccccc1C" -p 4

And here's another nonsensical result: chlorobenzene is supposedly more negative at the para C atom than anisole.

bob@epoch-virtual:synthesis$ evaluate -e "hmoElectrophilicLocalizationEnergy()" "c1ccccc1Cl" -p 4
bob@epoch-virtual:synthesis$ evaluate -e "hmoElectrophilicLocalizationEnergy()" "c1ccccc1OC" -p 4

User 25d107bd42

21-04-2011 01:32:19

Hi Bob,

Let us continue our long discussion about localisation energies we had some months ago.

In the next days I will present here some quantum chemical calculations on halogen benzenes,

and I will try to get hmo parameters from it.

Best regards, Hans-Ulrich

User 25d107bd42

25-04-2011 07:19:12


the quantum chemistry calculations take more time as estimated (as usual). It is not easy to find a common basis set for all four halogens. But before posting these results I will give some statements to this topic here:

In contrast to some of my sentences last year: The "old" localisation energy L(+) calculation method should not be deprecated and so it could still be used for reaction calculations. As scheduled by Jozsi in ftopic4757.html ,Mar 23, 2010, it should be renamed to 

"Reactor Localization Energies"

In the meantime I have learned how many special topologies and special substituents are implemented here, especially by Bobs suggestions and problem reports. So it should be possible to use this method, too. It is optimized to simulate reaction predictions, and this feature should be maintained in the future, too.

May be, I will help to produce a better documention, if that is the problem.

Best regards, Hans-Ulrich

User 870ab5b546

25-04-2011 18:01:14

It is indeed extremely difficult to find parameters that correctly predict the reactivity of both halobenzenes and other substituted benzenes.

However, I can use energyE() to get one reasonably accurate relative reactivity scale for halobenzenes and another reasonably accurate relative reactivity scale for other arenes.  The two scales don't correlate, but I can create separate reaction definitions for haloarenes and for other arenes.  I can send any particular arene to Reactor with the haloarene definition first; if Reactor fails to return any results, then I can send it to the more general definition.

Regardless, the point I was making above was that hmoElectrophilicLocalizationEnergy() is not parameterized for even toluene or trifluorotoluene, let alone bromo- and iodobenzene, so it is useless for making predictions about electrophilic aromatic substitution reactions.  For this reason alone, energyE() should not be deprecated.

ChemAxon e08c317633

26-04-2011 11:17:59

We will not remove the energyE() function completely, we just want to eliminate its connection to Huckel calculations, to avoid further misunderstanding.

energyE() function will be renamed.  "Reactor Localization Energies" is not a good name, we don't want to include a product name (Reactor) in a CT function name. Let us know if you have a suggestion how to name this function.


User 870ab5b546

26-04-2011 15:04:46

How about nucleophilicity() ?

User 25d107bd42

26-04-2011 15:46:36

Yes, indeed:

nucleophilicity() replacing energyE()

and also the opposite

electrophilicity() replacing energyNu()


Regards, Hans-Ulrich

ChemAxon e08c317633

28-04-2011 18:06:04

Thanks for the suggestions. We like the names "nucleophilicity()" and "electrophilicity()".