E2, E1

Nucleophilicity vs Basicity

• Nucleophilicity: kinetic concept, how good at reacting itself
• Basicity: thermodynamic concept, how badly this reaction would like to happen

(Note), before E1, E2 reactions:
I just realized SN2, SN1, E2, E1 are all talked in high school chemistry. They were not so deep-dived though.

SN2, SN1
Previous: SN2, SN1

	SN2	SN1
Rate	R = k[electrophile][nucleophile]	R = k[electrophile]
Electrophiles ("big barrier")	depends on steric hinderance; Primary > secondary > tertiary	depends on easiness of carbocation formation; Tertiary > secondary > primary
Nucleophile	strong (bearing negative charge)	weak (neutral)
Solvent	polar aprotic (DMSO/dimethylsulfoxide)	polar protic (alcohol, water)
chirality inversion	Yes	No

E2, E1

E: elimination, of base anion and proton.
Focus on Basicity, no Nucleophilicity.

Both forms a new CC π bond, eliminate a CH proton and a C-(leaving group); also both observe Zaitsev's rule.

How E2/E1 works:

e2-e1.png

Achtung⚠️:

• E2: leaving Hydrogen must be steric "anti" to leaving group
• E1: leaving group leaves first, then deprotonation.

	E2	E1
Rate	R = conc(base)(substrate)	R = conc(substrate)
big barrier	depends on steric hinderance; Primary > secondary > tertiary	depends on easiness of carbocation formation; Tertiary > secondary > primary
Basicity	strong	weak
Solvent	/	polar protic: good for ionization
stereo	leaving group must anti to hydrogen	/

Zaitsev Rule

Elimination reactions usually occur such that they are removing a hydrogen from the carbon attached to the fewest hydrogens.

In Elimination Reactions, The “More Substituted” Alkene Tends To Be The Major Product

Zaitsev.png

(more details to come)
~ Markovnikov rule

E.g. E2, E1

• E2: 1-bromopropane & sodium methoxide
• E1: 2-bromo-2-methylpropane & methanol

e2-e1-eg.png