E1 & E2 Reactions Cheat Sheet

These flashcards cover the key concepts, definitions, and mechanisms related to E1 and E2 reactions in organic chemistry.

Alkene Substitution

Refers to the process where an alkene undergoes replacement of one of its substituents.

Stability of Alkene

The stability increases from mono to tetra due to hyperconjugation and the number of alkyl donor groups.

E/Z Configuration

Cahn–Ingold–Prelog system used to assign priorities to substituents at a double bond; Z indicates substituents are on the same side, E indicates they are on opposite sides.

α-carbon

The carbon atom that is directly attached to the leaving group in a reaction.

β-carbon

The carbon atom adjacent to the α-carbon that has a removable hydrogen.

E2 Reaction Rate Law

Rate = k[substrate][base], indicating it is a one-step concerted reaction.

E1 Reaction Rate Law

Rate = k[substrate], indicating it is a two-step reaction involving carbocation formation.

Concentration Effects in E2

Increasing substrate or base concentration increases the rate of the E2 reaction.

Concentration Effects in E1

Increasing substrate concentration increases the rate, but increasing base concentration has no effect.

Choosing Between E1 & E2

E2 is favored with strong bases and 1° or 2° substrates, while E1 is favored with weak bases and 3° substrates.

Zaitsev’s Rule

States that the more substituted alkene is typically the major product of an elimination reaction.

Hofmann Product

The less substituted alkene product favored by bulky bases.

E2 Geometry

Requires that the β-hydrogen and the leaving group are in an anti-periplanar configuration.

Carbocation Rearrangements

In E1 reactions, carbocations may rearrange via 1,2-hydride or 1,2-methyl shifts to form a more stable carbocation.

Energy Diagram for E2

Consists of 1 step, 0 intermediates, and 1 transition state.

Energy Diagram for E1

Consists of 2 steps, 1 intermediate (carbocation), and 2 transition states.

Identifying Mechanism Based on Reagents

Strong bases lead to E2, weak bases with heat lead to E1, and different conditions result in SN1/E1 or SN2/E2 mixes.