energyE

Hi,





I typed,

Code:

cxcalc energyE "CC(C)C1=CC=CC=C1[N+]([O-])=O"

and I was told that it wasn't a legitimate function. But energyE is listed in the Chemical Terms table, and you use it in the Friedel-Crafts reaction definition.





Why is energyE more appropriate for Friedel-Crafts selectivity than other functions such as piChargeDensity?





-- Bob

The energyE function calculates the localization energy using a dummy electrophile to model the transition state.





Reference: Neil S. Isaacs, Physical organic chemistry, John Wiley & Sons, Inc., 1987





When Marvin and Reactor will support multiple step reactions (under development), we will be able to enhance the Chemical Terms language to perform calculations on the specific intermediers and transition states.

bobgr wrote:

I typed, Code: cxcalc energyE "CC(C)C1=CC=CC=C1[N+]([O-])=O" and I was told that it wasn't a legitimate function. But energyE is listed in the Chemical Terms table, and you use it in the Friedel-Crafts reaction definition.

Hi,





You can use Evaluator for evaluating Chemical Terms expressions.

Code:

evaluate -e "energyE()" "CC(C)C1=CC=CC=C1[N+]([O-])=O" ;;;3.22;2.47;2.68;2.65;2.68;3.01;;; evaluate -e "energyE(3)" "CC(C)C1=CC=CC=C1[N+]([O-])=O" 3.22

The electrophilic localization energy calculation is part of "energy" and "huckel" calculations in cxcalc.

Code:

cxcalc energy -s e "CC(C)C1=CC=CC=C1[N+]([O-])=O" id      Localization energy L(+) 1       ;;;3.22;2.47;2.68;2.65;2.68;3.01;;; cxcalc huckel -t localizationenergy:e "CC(C)C1=CC=CC=C1[N+]([O-])=O" id      Localization energy L(+) 1       ;;;3.22;2.47;2.68;2.65;2.68;3.01;;;

Zsolt

Gyuri wrote:

The energyE function calculates the localization energy using a dummy electrophile to model the transition state. Reference: Neil S. Isaacs, Physical organic chemistry, John Wiley & Sons, Inc., 1987 When Marvin and Reactor will support multiple step reactions (under development), we will be able to enhance the Chemical Terms language to perform calculations on the specific intermediers and transition states.

OK, but I still don't understand why you chose energyE() as the parameter for determining the regioselectivity of Diels-Alder reactions. Why not some other energy parameter?





The reason I ask is, the anilinium ion is giving both meta and ortho products in Friedel-Crafts reactions, and I don't understand why the ortho product is being obtained.

What do you suggest? Is there a more suitable calculation?





Pi charge density would not work well for the regioselectivity prediction of the aromatic acylation of halogenated aromatic compounds (bromobenzene), heterocycles (indole), and fused aromatic systems (anthracene).





I suppose, that the energyE function provides better results, and could be improved further in combination with a suitable steric effect calculation.





Anyway, if an other calculation can provide more precise directing predition, we can replace the current one. And certainly, you do not have to wait for us, as you can directly edit the rules of the reactions influencing their selectivity.





As soon as the representation of intermediates will be supported we will be able to incorporate other energy calculations, that can work with the special transition states and intermediates.

I'm just surprised at the result for C₆H₅NH₃⁺.

Code:

evaluate -e "energyE()" "[NH3+]C1=CC=CC=C1" -p 3 ;3.37;2.617;2.571;2.908;2.571;2.617

The difference between the ortho and meta values is much smaller than I would have expected. I would have expected the ortho value to be much closer to the para value. Not understanding how the energyE() value is obtained, it seemed to me that a calculation that gave a larger ortho value would be a more appropriate method.

Hi,








Yes, I think you are right.


With improved electron withdrawing parameters I obtained better results.


See. Fig.1.











Jozsi

How do I access these improved electron-withdrawing parameters? Or do I need to wait for the next version of JChem?

Hi,








You can access the improved version in the next release that will be available in 2 weeks.











Jozsi

Hi,





Will the next release be 3.2.12 or 5.0?





-- Bob

Hi,





Marvin and JChem 5.0 were released on January 9, 2008.





Jozsi