Reaction Mechanism Conditions – Flashcards

• 1^o with C⁺ stabilisation or 3^o
• Polar protic solvent
• Non-basic nucleophile

• Unhindered 2^o or 1^o carbon
• Good non-basic nucleophile
• Polar aprotic solvent

• 3^o, unhindered 2^o, unhindered 1^o
• Hindered strong base present
• Non-polar solvent (3^o)

• 3^o
• Strong base
• Polar solvent (with heat)
• Competes with Sn1

• High electron density - "the conjugate base is always a better nucleophile"
• Low electronegativity - electrons are less tightly held so are more easily donated (move across periodic table)

• Solvent - in polar protic (O-H, N-H, F-H) nucleophilicity increases down the periodic table due to capacity for hydrogen bonding (F has high capacity for hydrogen bonding - more hindered, electrons are less free moving). In polar aprotic nucleophilicity decreases down the periodic table because no hydrogen bonding
• Nucleophilicity decreases with bulkiness

Good leaving groups are weak bases

Strong acids give weak conjugate bases

Low pka, weak base

Must be a stable anion

Acidic C-H

Moderate/poor leaving group

Stable carbanion (established by resonance)

Poor leaving group

Positively charged substrate (biased towards cb through E2)

Bulky base in an E2 reaction causes it to preferentially remove the most accessible hydrogen due to steric effects

Least substituted (more hydrogens) alkene is formed as the major product

Always gives the most substituted alkene

E1: Because the reaction proceeds via the lower energy T.S

E2: Because the T.S is passed through during the RDS of the reaction these are more regioselective BUT the requirement for the removed proton to be anti-periplanar overrides all other considerations