Mechanism Arrow Placement [ENDORSED]

[Diondraya_Taylor_1C]

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

[Chem_Mod]

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]

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]

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]

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

[Chem_Mod]

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+