Charge not recognized in allylic cation (vs anion)

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JW_UMiami
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Joined: Thu Feb 11, 2021 8:51 pm
Full Name: James Wilson
Organization: University of Miami
Subdiscipline: Organic Chemistry

Charge not recognized in allylic cation (vs anion)

Post by JW_UMiami »

I've tried to show the MO and electrostatic potential maps in class, but ran into the following issue:

1. after constructing the molecule, I've changed the formal charge on the terminal carbon with out the pi bond to 1 (entered as +1).
2. After optimizing the geometry or using the remote server (which recognizes the +1 charge), generating the MOs shows the 2nd pi MO as occupied, i.e. at some point it has picked up a -1 charge.

The second pi MO is occupied in the cation:

Image

The electrostatic potential map of the cation and anion are the same, despite the difference in charge:

Image

Image

webmo
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Re: Charge not recognized in allylic cation (vs anion)

Post by webmo »

Can you please clarify the problem? Note that you must correctly specify the total charge of the molecule when running the actual calculation. The format charges do not actually enter a MO calculation. They are for display / generation of an initial geometry only.

Note that your images do not display, so that may be part of the confusion.

November_SSN
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Joined: Tue Mar 30, 2021 5:57 pm
Full Name: Paul McPherson
Organization: Saratov State Technical University

Re: Charge not recognized in allylic cation (vs anion)

Post by November_SSN »

I had run into a similar issue when using WebMO on my tablet in class last week, and it looks like I didn't indicate the charge of the molecule correctly. If I do it the right way, the problem does not appear again. Thank you for your explanation!

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