Reactivity And Electron-Pushing Arrows Chart
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4REACTIVITY A ND E LECTRON-‐PUSHING A RROWS
organic c hemistry
roles t hat a toms c an p lay i n r eactions
NUCLEOPHILES AND BASES
nucleophile: donates electrons to join an electrophile
base: donates electrons to receive a proton from an acid
So a nucleophile or base goes at the tail of an electron pushing arrow.
First, look for: negative formal charge
-
Otherwise, look for: δ
or lone pair, or a carbon-carbon pi bond
Neutral atoms with lone pairs are generally not nucleophilic unless they are bonded to at
least one hydrogen.
ELECTROPHILES AND ACIDS
electrophile: receives electrons to join a nucleophile
acid: receives electrons to donate a proton to a base
So an electrophile or acid goes at the head of an electron pushing arrow.
First, look for: positive formal charge
+
Otherwise, look for: δ
LEAVING GROUPS
leaving group: receives electrons to leave something
So a leaving group goes at the head of an electron pushing arrow.
First, look for: positive formal charge
Otherwise, look for: a neutral halogen (Cl, Br, or I);
or, a neutral atom whose negative charge after leaving will be resonance stabilized
effect o f f ormal c harges o n a toms’ r oles
rule
exception
negative
The atom with the negative
If the negative charge is on a metal or
formal charge
charge is the nucleophile or
semimetal (e.g., Al, B, or Fe), then the
base.
attached atom is the nucleophile or
base, and it donates the electrons from
its bond.
positive
The atom with the positive
If the positive charge is on a carbon,
formal charge
charge is the leaving group.
then the carbon is the electrophile.
The attached atom may act
No leaving group is necessary.
as an electrophile.
If the positive charge is on a hydrogen,
then the hydrogen is an acidic proton.
If the positive charge is on a metal, then
the metal is an unreactive spectator ion.
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