Diese Präsentation wurde erfolgreich gemeldet.
Wir verwenden Ihre LinkedIn Profilangaben und Informationen zu Ihren Aktivitäten, um Anzeigen zu personalisieren und Ihnen relevantere Inhalte anzuzeigen. Sie können Ihre Anzeigeneinstellungen jederzeit ändern.
Nächste SlideShare
What to Upload to SlideShare
What to Upload to SlideShare
Wird geladen in …3
×
1 von 19

ORGANIC INTERMEDIATES- CARBANIONS

6

Teilen

Herunterladen, um offline zu lesen

The slides contains the structural features, formation methods, stability and application of carbanion produces in organic reaction.

Ähnliche Bücher

Kostenlos mit einer 30-tägigen Testversion von Scribd

Alle anzeigen

Ähnliche Hörbücher

Kostenlos mit einer 30-tägigen Testversion von Scribd

Alle anzeigen

ORGANIC INTERMEDIATES- CARBANIONS

  1. 1. ORGANIC INTERMEDIATES CARBANIONS Presented by : Akshay kank (M Pharm First Year) Guided by : Dr. S.S. Pekamwar Sir SWAMI RAMANAND TEERTH MARATHWADA UNIVERSITY ( PHARMACEUTICAL SCIENCES), NANDED.
  2. 2. CONTENTS • INTRODUCTION • STRUCTURE OF CARBANIONS • FEATURES OF CARBANIONS • FORMATION METHOD • STABILITY OF CARBANIONS • SYNTHETIC APPLICATION • REFERENCES
  3. 3. INTRODUCTION • AN ANION IN WHICH CARBON HAS AN UNSHARED PAIR OF ELECTRONS AND CONTAINS A NEGATIVE CHARGE. • A CARBANIONS IS ONE OF THE REACTIVE INTERMEDIATES IN ORGANIC CHEMISTRY. • THE CONJUGATE BASES OF WEAK ACIDS, STRONG BASES, EXCELLENT NUCLEOPHILES.
  4. 4. INTRODUCTION • THE NEGATIVE CHARGE GIVES GOOD NUCLEOPHILE PROPERTIES AND IT CAN BE USED IN THE FORMATION OF NEW CARBON CARBON BOND. • BOND CLEAVAGE: HETEROLYTIC CLEAVAGE
  5. 5. STRUCTURAL FEATURES OF CARBANIONS • PYRAMIDAL- SP³ HYBRIDISED. • BOND ANGLE 109.28 • GEOMETRY IS THUS TETRAHEDRAL. • HAS EIGHT ELECTRONS. • STABILIZED BY RESONANCE OR BY INDUCTIVE EFFECT. • ACT AS BASE OR NUCLEOPHILE.
  6. 6. STRUCTURAL FEATURES • CARBANIONS UNDERGOES RAPID INTERCONVERSION BETWEEN TWO PYRAMIDAL FORMS. • THE ENERGY BARRIER IS DIFFERENT FOR DIFFERENT TYPES OF CARBANIONS. • THE HIGHER ENERGY BARRIER OF TRIFLUOROMETHYL CARBANIONS IS DUE TO THE MORE ELECTRONEGATIVITY OF FLUORINE ATOM WHICH IS MORE STABILIZING THAN A HYDROGEN ATOM.
  7. 7. FORMATION OF CARBANIONS • BY USING FOLLOWING WAYS: 1. PROTON ABSTRACTION 2. DECARBOXYLATION 3. ADDITION OF NUCLEOPHILE TO ALKENE 4. FORMATION OF ORGANOMETALLIC COMPOUND
  8. 8. FORMATION- PROTON ABSTRACTION • WHEN PROTON IS ABSTRACTED FROM A CARBON CENTRE THEN THE RESULTING ANION IS CALLED AS CARBANIONS • THE ACIDIC HYDROGEN OF AN ORGANIC SUBSTRATE CAN BE ABSTRACTED BY AN APPROPRIATE BASE FOR EXAMPLE CARBANIONS GENERATED FROM CARBONYL COMPOUND.
  9. 9. FORMATION – DECARBOXYLATION • DECARBOXYLATION OF CARBOXYLATE LEADS TO FORMATION OF CARBANIONS INTERMEDIATE.
  10. 10. FORMATION – ADDITION OF NUCLEOPHILE TO ALKENE • CARBANIONS ARE GENERATED BY THE ATTACK OF NUCLEOPHILES ON ONE OF THE CARBON OF AN ALKENE.
  11. 11. FORMATION – FORMATION OF ORGANOMETALLIC COMPOUND • METALS WHICH ARE LESS ELCTRONEGATIVE THAN CARBON(SUCH AS MAGNESIUM, LITHIUM, POTASSIUM, SODIUM, ZINC, MERCURY, LEAD, THALLIUM ETC.) • THUS, METALLATION REVERSE THE POLARITY OF THE CARBON FROM POSITIVE IN TO NEGATIVE IN ORGANOMETALLIC COMPOUND. • REACTION OF ALKYL HALIDE WITH LITHIUM FORM ALKYL LITHIUM HAVING NEGATIVE CHARGE ON CARBON.
  12. 12. STABILITY OF CARBANIONS • FACTORS WHICH CAN STABILIZE OR DISPERSE THE NEGATIVE CHARGE ON CARBON WILL STABILIZE A CARBANIONS • STABILITY DEPENDS UPON FOLLOWING FACTORS: 1. INDUCTIVE EFFECT 2. EXTENT OF CONJUGATION OF THE ANION 3. HYBRIDIZATION OF THE CHARGE BEARING ATOM 4. AROMACITY
  13. 13. 1. INDUCTIVE EFFECT • IF THE GROUPS ATTACHED TO CARBANIONS ARE ELECTRON RELEASING IN NATURE THEY WILL INCREASES THE NEGATIVE CHARGE ON CARBON AND THUS DISTABILIZE IT. • HOWEVER ELECTRONEGATIVE ATOMS(F, CL, BR) OR ELECTRON WITHDRAWING GROUPS (NO, CN, COOH, CO) ADJACENT TO THE NEGATIVELY CHARGED CARBON WILL STABILIZE THE CARBANIONS.
  14. 14. 2. EXTENT OF CONJUGATION OF THE ANION • IF NEGATIVELY CHARGED CARBON IS IN CONJUGATION WITH A DOUBLE BOND THE RESONANCE EFFECTS WILL STABILIZE THE ANION BY SPREADING OUT THE CHARGE BY REARRANGING THE ELECTRON PAIRS.
  15. 15. 3. HYBRIDIZATION OF THE CHARGE BEARING ATOM • STABILITY OF ANION WILL DEPENDS UPON THE ‘S’ CHARACTER OF CARBANIONS I.E MORE THE ‘S’ CHARACTER HIGHER WILL BE STABILITY OF ANION. • PERCENTAGE S CHARACTER IN THE HYBRID ORBITALS IS- SP(50%) > SP²(33%) > SP³(25%)
  16. 16. 4. AROMATICITY • IN SOME CARBANIONS THE LONE PAIR OF ELECTRON OF THE NEGATIVE CHARGE IS INVOLVED IN DELOCALIZATION TO ADD ON TO THE AROMATIC CHARACTER OF THE MOLECULE WHICH GIVES THEM EXTRA STABILITY. Cyclopentadienyl anion
  17. 17. SYNTHETIC APPLICATION OF CARBANIONS • CARBOCATION ARE STRONG LEWIS ACIDS WHILE CARBANIONS ARE STRONG BASES. SO THEY SHOWS MORE REACTIVITY TOWARDS EACH OTHER. • CARBANIONS ARE PART OF MOST OF THE COMMON REACTION TYPES SUCH AS- 1. DISPLACEMENT REACTION 2. ELIMINATION REACTION( E1 ) 3. CONDENSATION 4. ADDITION REACTION 5. REARRAGEMENT REACTION 6. POLYMERIZATION ETC.
  18. 18. REFERENCES • REACTIVE INTERMEDIATES IN ORGANIC CHEMISTRY STRUCTURE, MECHANISM AND REACTIONS BY MAYA SHANKAR SINGH, WILEY- VCH PUBLICATION. • ORGANIC CHEMISTRY AN INTERMEDIATES, TEXTBOOK, SECOND EDITION, BY ROBERT V. HOFFMAN, A JOHN WILEY AND SONS INC. PUBLICATION. • CARBANIONS AND FACTORS AFFECTING THEIR STABILITY, HTTPS://WWW.SLIDESHARE.NET/MOBILE/KOSKAL/CARBANIONS - 39935663 • ORGANIC CHEMISTRY TUTORIALS: CARBANIONS WWW.CHEM.UCLA.EDU/../CC.PDF • ORGANIC CHEMISTRY BY ROBERT MORRISON AND ROBERT BOYD, SEVENTH EDITION, PEARSON PUBLICATION
  19. 19. THANK YOU

×