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My book indicates that the following electron pushing is wrong:

enter image description here

So what would the right electron pushing diagram be?

I have the following in mind. My rationale is:

1) Electrons attack protons, not the other way around. This is just convention right? Is this just a conceit in chemistry; just a standardization? On a related note is this why one person described organic chemistry as:

"The foundation of every reaction in organic chemistry can be found in one statement: Nucleophile Attacks Electrophile."

Rather than electrophile attacks nucleophile?

2) Water is the base here; water is the Lewis Base (nucleophile) so water will attack the hydrogen cation (which is a bare nucleus). 3) HCl is the acid here; H+ is the Lewis Acid (electrophile, so it's going to go toward the lone pairs on the water).

So:

Would this be right?

enter image description here

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2 Answers 2

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If the electrons are to go somewhere, they should be attracted to that place. Consider the incorrect diagram you posted. The oxygen atom in water is partially negatively charged; the bonded electrons are drawn to the oxygen atom due to its high electronegativity. So it would not make much sense for the electrons in HCl to "attack" the oxygen atom, because the negative electrons would not be attracted the negative oxygen atom - in fact, they should be repelled.

Also, keep in mind that protons are rather stationary, at least where chemical reactions are concerned. It is the electrons that move around and form bonds to whatever compound is willing. Since "attack" is a verb of action, it helps to think of something mobile to carry out that action. The protons do not attack; the electrons do. Even in "electrophilic attacks", such as electrophilic addition, it is the electrons that move around and form bonds, even though the "disturbance" is provoked by something electrophilic.

My experience in organic chemistry is much like your quotee's. Just find out where the electrons go, and draw the schemes.

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  • $\begingroup$ Ah, I understand. Electrons are the mobile species. Electron flow characterizes reactions (and also conductivity). Electrons form bonds. Electrons are found in clouds and move around at will while protons are bound to the nucleus. I should have thought of the chemistry first and have attempted to answer my own question; like you say, the proton is quite stationary relative to the electron. $\endgroup$
    – Dissenter
    May 10, 2014 at 14:24
  • $\begingroup$ Yes, there you have it! The essence of chemistry :) $\endgroup$
    – Yoda
    May 10, 2014 at 14:34
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1) Nucleophiles often have excess electron density while electrophiles are characterized by a lack thereof. The electrons flow in the direction of lower electron density (and not the other way around), because they are "attracted" by the positive partial or formal charge of the electrophile. This is the reason why the first scheme from your book is wrong, because it shows a nucleophile attacking another nucleophile.

2), 3) and the reaction scheme you have drawn are correct.

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