Recommended
More Related Content
What's hot
What's hot (20)
Similar to Carbanions
Similar to Carbanions (20)
Recently uploaded
Recently uploaded (20)
Carbanions
- 1. © Ramaiah University of Applied Sciences 1 Faculty of Pharmacy © Ramaiah University of Applied Sciences 1 Faculty of Pharmacy © Ramaiah University of Applied Sciences 1 Faculty of Pharmacy © Ramaiah University of Applied Sciences 1 Faculty of Pharmacy Carbanions By Burhanuddin Madriwala M.Pharm – SEM I Department of Pharmaceutical Chemistry M.S Ramaiah University of Applied Sciences
- 2. © Ramaiah University of Applied Sciences 2 Faculty of Pharmacy © Ramaiah University of Applied Sciences 2 Faculty of Pharmacy © Ramaiah University of Applied Sciences 2 Faculty of Pharmacy © Ramaiah University of Applied Sciences 2 Faculty of Pharmacy Contents • Introduction • Structure & Properties • Classification • Stability • Carbanion formation • Reactions involving carbanions • summary
- 3. © Ramaiah University of Applied Sciences 3 Faculty of Pharmacy © Ramaiah University of Applied Sciences 3 Faculty of Pharmacy © Ramaiah University of Applied Sciences 3 Faculty of Pharmacy © Ramaiah University of Applied Sciences 3 Faculty of Pharmacy INTRODUCTION • Carbon atom having 3 bonds & bearing negative charge • Highly reactive species • Electron rich molecule • Unstable due to electron-electron repulsion (lone pair-bond pair) • Act as nucleophile
- 4. © Ramaiah University of Applied Sciences 4 Faculty of Pharmacy © Ramaiah University of Applied Sciences 4 Faculty of Pharmacy © Ramaiah University of Applied Sciences 4 Faculty of Pharmacy © Ramaiah University of Applied Sciences 4 Faculty of Pharmacy Structure & characteristics
- 5. © Ramaiah University of Applied Sciences 5 Faculty of Pharmacy © Ramaiah University of Applied Sciences 5 Faculty of Pharmacy © Ramaiah University of Applied Sciences 5 Faculty of Pharmacy © Ramaiah University of Applied Sciences 5 Faculty of Pharmacy • 3 bonds with one lone pair • Sp3 hybridised • Trigonal pyramidal structure • Bond angles 109.4° Characteristics • Electronic configuration – 1s2, 2s2 2p6 • Complete octet in outermost shell of carbon • Formed by heterolytic bond fission • Diamagnetic because all electrons are paired • Reactive towards electrophiles
- 6. © Ramaiah University of Applied Sciences 6 Faculty of Pharmacy © Ramaiah University of Applied Sciences 6 Faculty of Pharmacy © Ramaiah University of Applied Sciences 6 Faculty of Pharmacy © Ramaiah University of Applied Sciences 6 Faculty of Pharmacy Classification • Methyl carbanion • Primary carbanion • Secondary carbanion • Tertiary carbanion
- 7. © Ramaiah University of Applied Sciences 7 Faculty of Pharmacy © Ramaiah University of Applied Sciences 7 Faculty of Pharmacy © Ramaiah University of Applied Sciences 7 Faculty of Pharmacy © Ramaiah University of Applied Sciences 7 Faculty of Pharmacy • Allyl carbanion • Vinyl carbanion
- 8. © Ramaiah University of Applied Sciences 8 Faculty of Pharmacy © Ramaiah University of Applied Sciences 8 Faculty of Pharmacy © Ramaiah University of Applied Sciences 8 Faculty of Pharmacy © Ramaiah University of Applied Sciences 8 Faculty of Pharmacy • Benzylic carbanion • Phenylic carbanion
- 9. © Ramaiah University of Applied Sciences 9 Faculty of Pharmacy © Ramaiah University of Applied Sciences 9 Faculty of Pharmacy © Ramaiah University of Applied Sciences 9 Faculty of Pharmacy © Ramaiah University of Applied Sciences 9 Faculty of Pharmacy Stability
- 10. © Ramaiah University of Applied Sciences 10 Faculty of Pharmacy © Ramaiah University of Applied Sciences 10 Faculty of Pharmacy © Ramaiah University of Applied Sciences 10 Faculty of Pharmacy © Ramaiah University of Applied Sciences 10 Faculty of Pharmacy • Electron donating groups – alkyl, -OH, -NH2, R-O-R etc. decreases stability due to electron-electron repulsion • Electron withdrawing groups – CHO, COOH, CONH2, halogens (Cl¯,Br¯, F¯, I¯), R-CO-R etc. increases stability due to negative inductive effect.
- 11. © Ramaiah University of Applied Sciences 11 Faculty of Pharmacy © Ramaiah University of Applied Sciences 11 Faculty of Pharmacy © Ramaiah University of Applied Sciences 11 Faculty of Pharmacy © Ramaiah University of Applied Sciences 11 Faculty of Pharmacy Carbanion formation • By heterolytic fission CH3—H + ¯OH ¯CH3 + H2O • By addition reaction
- 12. © Ramaiah University of Applied Sciences 12 Faculty of Pharmacy © Ramaiah University of Applied Sciences 12 Faculty of Pharmacy © Ramaiah University of Applied Sciences 12 Faculty of Pharmacy © Ramaiah University of Applied Sciences 12 Faculty of Pharmacy Reactions involving carbanion intermediate • Aldol condensation – two aldehydes or ketones having alpha- hydrogen condense in presence of strong base to give ß- hydroxy aldehyde or ß-hydroxy ketone called aldol products. Reaction
- 13. © Ramaiah University of Applied Sciences 13 Faculty of Pharmacy © Ramaiah University of Applied Sciences 13 Faculty of Pharmacy © Ramaiah University of Applied Sciences 13 Faculty of Pharmacy © Ramaiah University of Applied Sciences 13 Faculty of Pharmacy Mechanism
- 14. © Ramaiah University of Applied Sciences 14 Faculty of Pharmacy © Ramaiah University of Applied Sciences 14 Faculty of Pharmacy © Ramaiah University of Applied Sciences 14 Faculty of Pharmacy © Ramaiah University of Applied Sciences 14 Faculty of Pharmacy • Crossed aldol condensation – between an aldehyde & ketone takes place in presence of base. • four products are formed- two cross & two direct products. Reaction
- 15. © Ramaiah University of Applied Sciences 15 Faculty of Pharmacy © Ramaiah University of Applied Sciences 15 Faculty of Pharmacy © Ramaiah University of Applied Sciences 15 Faculty of Pharmacy © Ramaiah University of Applied Sciences 15 Faculty of Pharmacy Summary • Carbanions are moiety having negative charge. • They are unstable & act as nucleophile. • Carbon is SP3 hybridised & have pyramidal structure. • They are stable in presence of EWG groups like NO2, CHO,COOH etc. & unstable with EDG like OH, NH2, -O- etc. • They are involved in many nucleophilic reactions like aldol condensation.
- 16. © Ramaiah University of Applied Sciences 16 Faculty of Pharmacy © Ramaiah University of Applied Sciences 16 Faculty of Pharmacy © Ramaiah University of Applied Sciences 16 Faculty of Pharmacy © Ramaiah University of Applied Sciences 16 Faculty of Pharmacy References • ‘Organic chemistry’ by Solomens.