SN2 , SN1 , E2 , & E1: Substitution and Elimination Reactions
SN2 , SN1 , E2 , & E1: Substitution and Elimination Reactions l Nucleophilic Substitution Reactions - SN2 Reaction: • Reaction is: o Stereospecific (Walden Inversion of configuration) o Concerted - all bonds form and break at same time o Bimolecular - rate depends on concentration of both nucleophile and substrate • Substrate:
Substitution and Elimination Reactions Comparative Chart
SN2 reaction Protic polar favors a SN1 reaction if the reactant is not charged Ex: H2O, CH3OH, etc Racemization (with some inversion because of ion pairing) E1 3>2>1 Forms a carbocation Weak base favors E1 reaction by disfavoring E2 reaction Not effected but a low concentration of base favors E1 by disfavoring a E2 reaction Protic polar
Four new mechanisms to learn: SN2 vs E2 and SN1 vs E1
Four new mechanisms to learn: SN2 vs E2 and SN1 vs E1 S = substitution = a leaving group (X) is lost from a carbon atom (R) and replaced by nucleophile (Nu:) N = nucleophilic = nucleophiles (Nu:) donate two electrons to carbon in a manner similar to bases donating to a
organic chemistry: SN2, E2, SN1, E1 - Freelance Teacher
N2, E2, S N1, E1 1 www freelance-teacher com S N2 S N1/E1 S N1 and E1 have identical rate determining steps, so they generally occur simultaneously and have the same properties E2 S N2 and E2 S N1/E1 mechanism one step—this single step is the rate-determining step (RDS) two steps—RDS is formation of carbocation big obstacle S
Practice reactions from CH 11 – SN2, E2, SN1, E1
Practice reactions from CH 11 – SN2, E2, SN1, E1 Give the major organic product of the following reactions Also, state the mechanism through which each reaction proceeds (e g SN2) (Do not draw out the mechanism ) KOC(CH3)3 in (CH3)3COH b) OTs c) Br Br CH3CH2CH2OH warm d) CH 3 CH2CH3 H OTs KCN in acetone, 20oC e) Br f) I CH3 NaSCH2CH3 in
Practice Problems on SN1, SN2, E1 & E2 - Answers
N2, E1 & E2 - Answers 1 Describe the following chemical reactions as S N1, S N2, E1 & E 2 Draw a curved arrow mechanism for each reaction NaI 3 3 Cl KCN DMSO CN Br NaOH H2O, heat BrH 2O OH I CH3CH2O-Na+ ethanol HI NaSH DMSO HSH Br HO KOH DMSO OTs NaNH2 NH3 TsO NH3 H2N O O CH CH3 TsO acetone O O CH CH3 I SN2 E2 SN1 SN2 E2 SN2 E2 SN1 SN2
Practice Problems on SN1, SN2, E1 & E2
N2, E1 & E2 1 Describe the following chemical reactions as S N1, S N2, E1 & E 2 Draw a curved arrow mechanism for each reaction NaI 3 3 Cl KCN DMSO CN Br NaOH H2O, heat BrH 2O OH I CH3CH2O-Na+ ethanol HI NaSH DMSO HSH Br HO KOH DMSO OTs NaNH2 NH3 TsO NH3 H2N O O CH CH3 TsO acetone O O CH CH3 I
SN2 S 1 - MIT OpenCourseWare
E2 yes no What kind of substrate? methyl or 1° S N2 3° yes mostly E1* 2° no mostly S N1* What kind of substrate? 2°, 3°, or stabilized 1° 1° S N2 + E2 Is Nuc/Base bulky? Unfavorable Reaction Start * Under conditions that favor a unimolecular reaction (weak nuc/base and polar protic solvent), mixtures of S N1 and E1 are usually obtained
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