Mechanism Arrow Placement  [ENDORSED]

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Diondraya_Taylor_1C
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Mechanism Arrow Placement

Postby Diondraya_Taylor_1C » Wed Mar 08, 2017 7:51 pm

How do you know if the arrow for a mechanism should be drawn from the actual element or from the bond?

Chem_Mod
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Re: Mechanism Arrow Placement

Postby Chem_Mod » Wed Mar 08, 2017 8:02 pm

Arrows shouldn't be drawn from an atom. Arrows are always drawn from an electron-rich source (lone pair or double bond) to an electron-deficient sink.

In electrophillic addition, an arrow is drawn from an alkene (double bonds are electron-rich) to an electrophile (partially or fully positive species).

In nucleophillic substitution, an arrow is drawn from the lone pair of a nucleophile (partially or fully negative species) to a partially positive carbon (the electrophile in this case).

Arrows can point toward an atom, if a bond is to be formed with that atom, but arrows are never drawn directly from an atom. Rather, they can be drawn from the lone pairs of an atom.

MayaKhalil_1L
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Re: Mechanism Arrow Placement  [ENDORSED]

Postby MayaKhalil_1L » Wed Mar 08, 2017 8:03 pm

It should always be drawn from the bond or lone pairs because that is where the electrons are coming from. Arrows are always drawn from electron rich areas to electron deficient.

Andrea Medina 1A
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Re: Mechanism Arrow Placement

Postby Andrea Medina 1A » Wed Mar 15, 2017 8:40 pm

when there is a molecule such as Br2 why is it that the arrow goes toward the delta negative? or does it depend on the equation?

MayaKhalil_1L
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Re: Mechanism Arrow Placement

Postby MayaKhalil_1L » Sun Mar 19, 2017 12:51 am

Br2 has a polar-covalent bond, so the delta negative atom is electron withdrawing, therefore attracting the electrons of the bond

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Re: Mechanism Arrow Placement

Postby Chem_Mod » Sun Mar 19, 2017 12:52 am

Andrea Medina 1A wrote:when there is a molecule such as Br2 why is it that the arrow goes toward the delta negative? or does it depend on the equation?


The arrow goes to the δ+


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