SN1 and SN2. E1 and E2. Rearrangement reaction.pptx

In this seminar (MPC102T) i have briefly discussed about Sn1, Sn2 , E1, E2 reactions.
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1. SN1 and SN2 E1 and E2 (Saytzeff, Hoffman rule) Rearrangement reaction By Shivam Gupta (SPER, Jamia hamdard ) M.Pharm (1 st Sem)

2. Nucleophilic substitution reaction Initiated by nucleophile = nucleophile substitution reaction In this type of reaction, a nucleophile react with substrate generally haloalkane having partial positive charge on carbon atom bonded to halogen. Nu - + C---X C—Nu + X -

3. Examples of SN reaction RX + OH - ROH + X - 2RX + Na R---R + 2Na (Wurtz) RX + OR’ ROR’ (Williamson) RX +SH - RSH RX + Ar + AlCl 3 ArR ( Friedal craft)

4. Leaving group I > Br > Cl > H 2 SO 4 > F > CH 3 COO - > > OH -- > H - > CH 3

5. Bimolecular = rate depend on reactant and base Nucleophile attack the reactive center from the opposite side of leaving group Order : 1 o alkyl halide > 2 o > 3 o In polar aprotic solvent Walden inversion ( R S ) SN2

6. Energy diagram for SN2 reaction

7. Unimolecular = rate depend only on one reactant Occur in two step and formation of carbocation is rate determining step Order = 3 o > 2 o > 1 o In polar protic solvent Racemic mixture is obtained SN1

8. SN1 Mechanism: Stereochemistry of SN1 reaction:

9. Energy Diagram for SN1 reaction

10. Comparison between SN1 and SN2 SN1 SN2 Rate Alkyl halide Alkyl halide + Nu -- Steps 2 1 Stereochemistry Racemic mixture R S Order of reaction 3 > 2 > 1 1 > 2 > 3 Solvent Polar protic Polar aprotic

11. Organic compound with an electronegative atom or electron withdrawing group bonded to sp 3 undergoes substitution or elimination rection. Halide ion are good leaving group substitution of this group give wide variety of compound (R—F, R—CL, R--Br) Unimolecular = alkyl halide Two step process : loss of leaving group followed by base attack to neighbouring H E1

12. E1 reaction energy Diagram E1 reaction mechanism :

13. Single step elimination Biomolecular = alkyl halide and base Dehydrohalogenation Order = 1 > 2 > 3 E2

14. SAYTZEFF AND HOFFMAN RULE: Elimination will occur such that H is removed from beta carbon with fewest hydrogens or the product should be highly substituted and vice versa for Hoffman .

15. Rearrangement reactions Rearrangement reaction is a wide class of organic reactions in which carbon skeleton of a molecule is rearranged to give a structural isomer of the orignal molecule. Substituent move from one atom to another atom in the molecule. Factor influencing rearrangement : Stability of intermediates , Thermodynamic (entropy) , steric hindrance

16. 1. Rearrangement to electron deficient carbon : Wagner Merwin rearrangement Pinacol rearrangement benzilic acid rearrangement Arndt Eistert homologation rearrangement 2. Rearrangement to electron deficient nitrogen : Hofmann rearrangement Curtius rearrangement Schmidt rearrangement Lossen rearrangement Beckmann rearrangement 3. Rearrangement to electron deficient oxygen : Baeyer villiger oxidation Dakin reaction Classification

17. 4. Rearrangement to electron rich carbon : Stevens rearrangement Sommelet Hauser rearrangement Wittig rearrangement Favorskii rearrangement 5. Aromatic rearrangement: Benzidine rearrangement Fries rearrangement Claisen rearrangement

18. Wagner Merwin Rearrangement:

19. Loosen rearrangement:

20. Baeyer villiger oxidation

21. References Smith M, March J. March’s advanced organic chemistry : reactions, mechanisms, and structure. Hoboken, N.J.: John Wiley & Sons; 2007. Sykes P. A guidebook to mechanism in organic chemistry. Noida, U.P., India Pearson; 6 th edition . SN1 and SN2 Reaction of Haloalkanes - SN1 Reaction, SN2 Reaction, Comparing SN1 and SN2 Reactions [Internet]. BYJUS. Available from: https://byjus.com/chemistry/sn1-and-sn2-reaction-of-haloalkanes/

22. THANKYOU