SN2 , SN1 , E2 , & E1: Substitution and Elimination Reactions
Elimination Reactions - E2 Reaction: • Reaction is: o Stereospecific (Anti-periplanar geometry preferred, Syn-periplanar geometry possible) o Concerted - all bonds form and break at same time o Bimolecular - rate depends on concentration of both base and substrate o Favoured by strong bases Elimination Reactions – E1 Reaction: • Reaction is:
Alkyl Halides Substitution and Elimination
• The reaction is concerted (all four bonds are made and broken at the same time) 4 1 Product Selectivity in E2: Saytzeff Rule (or Zaitsev, etc ) The Saytzeff Rule: Most substituted alkene is formed in an E2 reaction, if possible Example • When more than one alkene isomer can be formed in an E2 elimination, the more substituted, more stable
Ch 11 HW Set: Substitution and Elimination
Give the major product of the reaction and the mechanism by which it is produced (SN2 and E2 only for this set of reactions; we will add in SN1 /E1 later) Be sure to include the stereochemical outcome a 1° halide, good nucleophile, SN2 b special case: 1° halide but non-nucleophilic, strong base, E2 c
The Study of Elimination Reactions W Using Gas Chromatography
vestigation of an elimination reaction by GC–MS; however, it includes a lengthy preparatory synthesis and requires mass spectral analysis that is not suitable for our second-year lab Cabay et al (2) provide a procedure for the analysis of the stereochemistry of an E2 elimination, but the experiment re-
Reaction Mechanisms - IITPK
benzene ring via resonance Aryl halides undergo SN reaction when a strong electron-withdrawing group (or activating group) is present at the ortho and para positions ArSN reactions are of two types viz (i) Addition-Elimination reaction (ii) Elimination-Addition reaction via benzyne mechanism (i) Addition-Elimination reaction (also called
Chapitre 9 : substitution nucléophile et -élimination
S’iln’existepas d’intermédiaires réactionnels dans laréaction,lastructureserapprocherades réactifs pour une réaction exothermique et des produits pour une réaction endothermique Ce postulat de Hammond sera d’unegrandeimportancedansl’analysedelasélectivité
Chem 14D Exam 1
needed to accomplish the following E1 elimination Please place your answer in the box provided around the reaction arrow (5 points) Me H OH Me H TsOH benzene heat 9) Consider the 3-D depiction of the compound shown below Would you expect this substrate to readily undergo E2 elimination if treated with typical E2 reaction conditions? Circle
The E1 Mechanism in Photo-Induced β-Elimination Reactions for
Thus, the E1 reaction does not require a strong base In the red chromophores of both Kaede and EosFP, the C = C double bond between His62-C a and His 62-C b assumes a trans configuration(Mizunoetal ,2003;Nienhausetal ,2005;Hayashi et al , 2007) A reaction model based on the E2 mechanism has been proposed for the b-elimination of EosFP
**YOU ARE NOT ALLOWED TO TAKE SPARE COPIES OF THIS EXAM FROM
c) Draw the transition state for E2 elimination using Na+ –O-t-Bu as the base d) Give the E2 elimination product lowest energy chairE2 chair BrEt Me Me Br Et Et HMe E2 product Br H Et Et H Me O-t-Bu ‡ E2 transition state E2 product ‡ Me Br t-BuOHEt Me Et Question 7 (20 pts ) Indicate whether you would expect each reaction to be SN1, SN2
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