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What are the partial charges of on the atoms in a SN2 reaction?

The nucleophile is normally negatively charged and has a lone pair of electrons. This would make you think the transition state would have a negative charge on the nucleophile. The leaving group also is taking the electrons from the molecule with it. So what is the charge separation?

Here are conflicting images.

First image

enter image description here

Second image

enter image description here

Martin - マーチン
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user9995331
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    Not quite sure what you mean by So what is the charge separation? For SN2 reaction of bromide with chloroethane, bromide has -1 charge as reaction "starts" and chloride has -1 charge when the reaction "ends." – MaxW Jul 30 '18 at 01:15
  • I added some links for clarification. – user9995331 Jul 30 '18 at 13:34
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    ? I don't see any "conflict" between the links. What do you think is different/wrong? – MaxW Jul 30 '18 at 14:15
  • One has negative charges on both the nucleophile and leaving group. The other has a positive charge on the nucleophile and a negative charge on the leaving group. – user9995331 Jul 30 '18 at 17:06
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    That just isn't correct. For which of the images do you think that there is a positive charge on the nucleophile?!? For the second the leaving atom isn't even shown... – MaxW Jul 30 '18 at 17:17
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    Take a closer look at the second image. There are partial negative charges on the nucleophile and the leaving group, and a partial positive charge on the carbon center. Your images are in accordance with one another. – ringo Jul 30 '18 at 17:26
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    The problem here is you're reading more into partial charge than you should. If ever you take 2 partial negatives and a partial positive, and you can tell the total charge, something is wrong. It's not that detailed. – Zhe Jul 30 '18 at 17:44
  • So sorry, I linked the wrong image for the second link. https://qph.fs.quoracdn.net/main-qimg-5e8619e5b488fb01d32d2fb51c861fa8-c – user9995331 Jul 30 '18 at 17:46
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    Again, I don't see a problem.... – MaxW Jul 30 '18 at 18:03
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    Second image has a positive charge on the nucleophile. The first image has a negative charge on the nucleophile. What is correct? – user9995331 Jul 30 '18 at 18:06
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    Well they are both just diagrams and imperfect representations of what happens. In the second diagram the molecule being attacked is shown with a charge imbalance. I interpret the $\delta^+$ on the nucleophile in the middle image to mean that the positive charge is moving off the molecule being attacked and onto the nucleophile. Hence the nucleophile is donating an electron and the electron is going to the iodine atom which is shown with $\delta^-$. – MaxW Jul 30 '18 at 18:32
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    I think this illustrates nicely why looking at multiple sources is good. Two different representations get you thinking about what is really going on... – MaxW Jul 30 '18 at 18:35
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    I am more used to seeing the first image... It may depend on whether the nucleophile is initially charged. Maybe we may see a partial positive charge on the nucleophile in the TS if it was originally uncharged and we may see a partial negative charge if it was originally negatively charged. – Tan Yong Boon Jul 31 '18 at 08:16
  • I would regard the second image as wrong. – Martin - マーチン Aug 02 '18 at 18:59
  • I suspect that the second image is a typo, and where there is delta+, it should read delta-. – jerepierre Aug 02 '18 at 23:16

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