Elementary Steps of Reaction Mechanisms Flashcards
1,2-Rearrangement (1,2R)
Involves the shift of a sigma bond to an adjacent carbocation,
resulting in the formation of a new carbocation
Departure of an electrofuge (De)
The reverse of Ae , cleavage of a bond beta to a carbocation with formation of a
Cα =Cβ pi bond and loss of a group that does not retain the electrons in the Cα —Cβ bond, an electrofuge
Attack of an electrophile at a pi bond (Ae)
Resembles the An step, but the nucleophile uses
a pi bonding pair rather than a nonbonding lone pair to bond to a six-electron center
Beta-elimination of a nucleofuge (Ebeta)
A kind of Dn in which the leaving group is “pushed out”
by a beta lone pair that is moved into a new pi bond
Bimolecular elimination (E2)
Combines proton transfer with simultaneous loss
of a leaving group (nucleofuge) in a beta position with respect to the lost proton
Bimolecular nucleophilic substitution (Sn2)
Involves simultaneous formation of a bond via donation of a
nonbonding pair from a nucleophile and cleavage of a bond with loss of a leaving group (nucleofuge)
Proton transfer (pt)
Involves donation of a nonbonding pair or pi bonding pair to H in H—X, with simultaneous
heterolytic cleavage of the H—X bond toward X, a relatively electronegative atom or group
Departure of a nucleofuge (Dn)
Involves the loss of a group that takes the pair of electrons in the
broken bond with it, a leaving group
Addition of a nucleophile to a polarized pi bond (Adn)
Involves the donation of a nonbonding pair of electrons
in the nucleophile to the less electronegative element in a polarized pi bond X=Y (or X≡Y) in the electrophile
Attack of a nucleophile at a six-electron center (An)
Donation of a non-bonding pair of electrons in the nucleophile to a six-electron center (carbocation, neutral group-13 element, etc.) in the electrophile
Involves the shift of a sigma bond to an adjacent carbocation,
resulting in the formation of a new carbocation
1,2-Rearrangement (1,2R)
The reverse of Ae , cleavage of a bond beta to a carbocation with formation of a
Cα =Cβ pi bond and loss of a group that does not retain the electrons in the Cα —Cβ bond, an electrofuge
Departure of an electrofuge (De)
Resembles the An step, but the nucleophile uses
a pi bonding pair rather than a nonbonding lone pair to bond to a six-electron center
Attack of an electrophile at a pi bond (Ae)
A kind of Dn in which the leaving group is “pushed out”
by a beta lone pair that is moved into a new pi bond
Beta-elimination of a nucleofuge (Ebeta)
Combines proton transfer with simultaneous loss
of a leaving group (nucleofuge) in a beta position with respect to the lost proton
Bimolecular elimination (E2)
