Chapter 8: Substitution and Elimination Reactions
Ch. 8 – Substitution and Elimination Reactions
DAT Organic Chemistry Outline
Chapter 8: Substitution and Elimination Reactions Lesson 8.1 – Substitution Reactions SN1 Reaction – Substitution Nucleophilic Unimolecular Rate = k[electrophile]
SN2 Reaction – Substitution Nucleophilic Bimolecular Rate = k[electrophile][nucleophile]
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Ch. 8 – Substitution and Elimination Reactions
DAT Organic Chemistry Outline
Lesson 8.1 – Substitution Reactions Basics (Continued) Choosing between SN1 and SN2 reactions 1. Is the carbon bonded the leaving group 1º, 2º, or 3º?
2. Is my nucleophile strong or weak? a. Strong nucleophiles have negative charges. i. Exceptions: negative charges on halogens (Cl–, Br–, l–) or negative charges that are resonance-stabilized are weak. b. Some strong nucleophiles (SN2 reactions): CN-, OR-, OH-, RS-, NR2-, Rc. Some weak nucleophiles (SN1 reactions): RCO2–, HOR, H2O, HSR, HNR2, I–, Br– , or Cl–
SN2 vs. SN1 reactions
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Ch. 8 – Substitution and Elimination Reactions
DAT Organic Chemistry Outline
Lesson 8.2 – Elimination Reactions E1 Reactions – Elimination Unimolecular Rate = k[substrate]
•
Forms most substituted double bond (Zaitsev’s Rule)
Zaitsev’s Rule • E1 and E2 reactions give the more substituted C=C bond and favor the E-alkene.
E2 Reactions – Elimination Bimolecular Rate = k[substrate][base]
• • •
H and Leaving Group must be anti-periplanar (anti-coplanar) Forms most substituted double bond (Zaitsev’s Rule) Forms least substituted double bond if bulky base is used like t-butoxide (CH3)3CO-
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Ch. 8 – Substitution and Elimination Reactions
DAT Organic Chemistry Outline
Lesson 8.2 – Elimination Reactions (Continued) Choosing between SN1 and SN2 reactions 1. Is the carbon bonded the leaving group 1º, 2º, or 3º, or stabilized?
2. Is my base strong or weak? a. Strong bases have negative charges. i. Exceptions: negative charges on halogens (Cl–, Br–, l–) or negative charges that are resonance-stabilized are weak. b. Some strong bases (E2 reactions): OR-, OH-, RS-, NR2-, Rc. Some weak bases (E1 reactions): RCO2–, HOR, H2O, HSR, HNR2, I–, Br–, or Cl–
E2 vs. E1 reactions
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Ch. 8 – Substitution and Elimination Reactions
DAT Organic Chemistry Outline
Lesson 8.3 – Choosing Between SN1, SN2, E1, E2 Protic solvents = SN1 and E1 reactions Aprotic solvents = SN2 and E2 reactions Aprotic solvents: DMSO, DMF, THF, ether, acetone
Substitution vs. Elimination Flowchart
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DAT Organic Chemistry Outline
Chapter 8: Substitution and Elimination Reactions Lesson 8.1 – Substitution Reactions SN1 Reaction – Substitution Nucleophilic Unimolecular Rate = k[electrophile]
SN2 Reaction – Substitution Nucleophilic Bimolecular Rate = k[electrophile][nucleophile]
© DAT Bootcamp
1 of 5|Page
Ch. 8 – Substitution and Elimination Reactions
DAT Organic Chemistry Outline
Lesson 8.1 – Substitution Reactions Basics (Continued) Choosing between SN1 and SN2 reactions 1. Is the carbon bonded the leaving group 1º, 2º, or 3º?
2. Is my nucleophile strong or weak? a. Strong nucleophiles have negative charges. i. Exceptions: negative charges on halogens (Cl–, Br–, l–) or negative charges that are resonance-stabilized are weak. b. Some strong nucleophiles (SN2 reactions): CN-, OR-, OH-, RS-, NR2-, Rc. Some weak nucleophiles (SN1 reactions): RCO2–, HOR, H2O, HSR, HNR2, I–, Br– , or Cl–
SN2 vs. SN1 reactions
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2 of 5|Page
Ch. 8 – Substitution and Elimination Reactions
DAT Organic Chemistry Outline
Lesson 8.2 – Elimination Reactions E1 Reactions – Elimination Unimolecular Rate = k[substrate]
•
Forms most substituted double bond (Zaitsev’s Rule)
Zaitsev’s Rule • E1 and E2 reactions give the more substituted C=C bond and favor the E-alkene.
E2 Reactions – Elimination Bimolecular Rate = k[substrate][base]
• • •
H and Leaving Group must be anti-periplanar (anti-coplanar) Forms most substituted double bond (Zaitsev’s Rule) Forms least substituted double bond if bulky base is used like t-butoxide (CH3)3CO-
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Ch. 8 – Substitution and Elimination Reactions
DAT Organic Chemistry Outline
Lesson 8.2 – Elimination Reactions (Continued) Choosing between SN1 and SN2 reactions 1. Is the carbon bonded the leaving group 1º, 2º, or 3º, or stabilized?
2. Is my base strong or weak? a. Strong bases have negative charges. i. Exceptions: negative charges on halogens (Cl–, Br–, l–) or negative charges that are resonance-stabilized are weak. b. Some strong bases (E2 reactions): OR-, OH-, RS-, NR2-, Rc. Some weak bases (E1 reactions): RCO2–, HOR, H2O, HSR, HNR2, I–, Br–, or Cl–
E2 vs. E1 reactions
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Ch. 8 – Substitution and Elimination Reactions
DAT Organic Chemistry Outline
Lesson 8.3 – Choosing Between SN1, SN2, E1, E2 Protic solvents = SN1 and E1 reactions Aprotic solvents = SN2 and E2 reactions Aprotic solvents: DMSO, DMF, THF, ether, acetone
Substitution vs. Elimination Flowchart
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