Indicate which characteristics describes or favor E1, E2, Sn1, and Sn2 reactions
ID: 792414 • Letter: I
Question
Indicate which characteristics describes or favor E1, E2, Sn1, and Sn2 reactions question.?
Second order reactions
First order reactions
Carbocation intermediate
Substrate is primary halidebase is unhindered
Substrate is primary halidebase is hindered
Substrate is secondary halidebase is weak
Substrate is secondary halidebase is strong
Substrate is tertiary halidebase is weak
Substrate is tertiary halidebase is strong
One stereoisomer produced
Mixture of stereoisomers produced
Polar, protic solvent used
Explanation / Answer
E1
-Two steps: 1. Carbon-Halide bond breaks
2. Hydrogen is eliminated
-Occurs with tertiary alkyl halides and sometimes secondary alkyl halides. Because these are bulky, they favor the smaller bases rather than bulky bases like E2 which have trouble accessing the protons.
-Usually weak nucleophile. HOMe, H2O, H3CSH for example.
-Competes with SN1 due to having a common intermediate (carbocation) adding heat will favor E1 over SN1
-Can have carbocation rearangements
-Regioselective. Follow Zaitsev's rule and will form the more stable alkene.
E2
-One Step: Base removes proton, proton donates electrons to form double bond and kicks off halide.
-Occurs with primary alkyl halides and sometimes secondary alkyl halides. This is because the strong bulky base cannot remove protons from a bulky alkyl halide. These primary and secondary alkyl halides have readily accessible protons.
-Polar aprotic solvent
- Beta hydrogen and alpha halide must have an antiperiplanar relationship (180 degrees)
Here is a chart for you. I will try my best to reprint it (from my college notes). If you have an questions ask.
Tertiary Alkyl Halides + strong nuc = E2
Tertiary Alkyl Halides + strong/bulky nuc = E2
Tertiary Alkyl Halides + weak nuc = SN1 +E1
Secondary Alkyl Halides + strong nuc = E2 + SN2
Secondary Alkyl Halides + strong/bulky nuc = E2
Secondary Alkyl Halides + weak nuc = E1 + SN1
Primary Alkyl Halides + strong nuc = SN2 + E2
Primary Alkyl Halides + strong/bulky nuc = SN2 + E2
Primary Alkyl Halides + weak nuc = NO RXN
Strong nuc = NaOMe
Strong/bulky nuc = NaO(CH3)3
Weak nuc = HOMe