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Projection formulae
- 1. SUBMITTED BY :-Kritika Chandel PROJECTION FORMULAE
- 2. A two-dimensional representationof a three- dimensional molecular structure that indicates the spatial arrangement of bonds; a stereochemical formula. Examples of stereoformulae are :- Flying Wedge projection Newman projection Sawhorse projection Fischer projection INTRODUCTION
- 3. FLYING WEDGE PROJECTION This kind of representation is usually done for molecules containing chiral centre. A solid Wedge ( ) represents a bond above the plane of the paper and a dashed wedge or a broken line represents a bond below the plane of the paper.
- 4. For example :- C H3 C H3H OH bonds in the plane of the paper bond bellow the plane of the paper bond above the plane of the paper (R) - Lactic acid
- 5. NEWMAN PROJECTION In theseFormulae the molecule is viewed from the front. The carbon atom away from the viewer is called 'rear' carbon and is represented by a circle. The carbon atom facing the viewer is called 'front' carbon and is represented by dot. The remaining bonds on each carbon are shown by small straight lines. Newman Projection Out of sight three groups emanating from circumfrance Rear Carbon Visible Front Carbon
- 6. The concept ofNewman projection for n - butane can be understood by the following drawings: These conformations arise due to free rotation about the carbon - carbon single bond (front and rear carbon atoms). Staggered Eclipsed H H H H3C CH3 H CH3 H H H H CH3
- 7. SAWHORSE PROJECTION Thebond between two carbon atoms is shown by a longer diagonal line because we are looking at this bond from an oblique angle. The bonds linking other substituent to these carbons are shown projecting above or below this line. Eclipsed Staggered CH3 H H H H H3C 1 4 3 2 H H H H CH3 H3C
- 8. FISCHER PROJECTION AFischer projection formula is an effective way to show a molecule having more than one chiral carbon atom. In Fischer Formula, if two like groups are on the same side, the molecule is called ‘Erythro” and if two like groups are on opposite side it is called ‘threo’ .
- 9. The vertical linerepresents bonds extending into the plane of the page, whereas the horizontal line represents bonds extending out of the plane of the page. or (I) CH2OH OH COOH H C Towards the veiwer Away from the veiwer (I) OH H CH2OH COOH
- 10. •Rotation of aFischer projection by an angle of 1800 about the axis which is perpendicular to the plane of the paper gives identical structure. • However, similar rotation by an angle of 900 produces non - identical structure.
- 11. Fischer D andL projection nomenclature Glyceraldehyde is used as a standard for assigning relative configurations.
- 12. The bottom mostcarbon far away from the oxidized end is then taken into consideration. If OH / NR2 group on that carbon is present on the right(dextro) the molecule is assigned D configuration and if present on the left (laevo) then L configuration.
- 13. R S SYSTEM Thissystem is based on certain rules called as sequence rules and also as CIP rules. Step I: Assign a sequence of priority 1,2,3 and 4 where number 1 is assigned to group of highest priority and 4 is assigned to the group of lowest priority. Step II: Move your eye from the group of priority number 1 to group of priority number 3 via the group of priority number 2. Step III: If during this movement your eye travels in the clockwise direction, the molecule under examination is designated as R and if it moves in the anticlockwise direction it is designated as S.
- 14. Our eye movesin clockwise direction, so the absolute configuration of (–)-2- butanol is R. CH2CH3 H3C OH (Third Highest) (Second Highest) (Highest) 1 3 2
- 15. SEQUENCE RULES 2 4 1 3 D H3C Br H Iftwo isotopes of the same element are attached to the chirality centre, the atom with higher mass number is given higher priority.
- 16. In case thegroup attached to the chiral carbon contains a double bond or a triple bond, both atoms joined by multiple bonds are considered to be duplicated (in case of a double bond) and triplicate (in case of a triple bond).
- 18. Conversion of FischerProjection into Sawhorse Projection. H OH HO H COOH COOH 1 2 3 4 Eclipsed HO H H OH COOH HOOC Rotation by 180o along C2 - C3 axis Staggered COOH H HO HO H COOH 1 2 3 4 Front carbon Rear carbon Fischer Projection Sawhorse Projection
- 19. Conversion of Sawhorseprojection into Fischer projection 180o Rotation by CH3 CH3 H Br Br H Rear carbon Front carbon Sawhorse Projection H Br H CH3 CH3 Br Eclipsed Fischer Projection CH3 Br H H Br Staggered Sawhorse Projection CH3
- 20. Conversion of Sawhorseto Newman to Fischer Projection Staggered Sawhorse Projection Ph OH Br H2 N Cl CH3 View through the front carbon Br OH CH3 Ph H2N Cl HO Br Ph Cl NH2 H3C Front carbon Cl Br Ph CH3 HO H2N Hold in vertical plane keeping front carbon as the lowest Rotate the front carbon along the central Staggered Newman Projection Eclipsed Newman Projection Front carbon bond by 180o Fischer Projection Rear carbon
- 21. Conversion of Fischerto Newman to Sawhorse Projection Rotate front carbon by 180o HOH2C H H OH CHO Cl Staggered Sawhorse Projection Staggered Newman Projection OH H CH2OH CHO H Cl View through central bond Eclipsed Newman Projection CH2OH Cl H OH H CHO H H CHO CH2OH Cl OH Front carbon Rear carbon Fischer Projection
- 22. Conversion of FischerProjection into Flying Wedge The vertical bonds in the Fischer projection are drawn in the plane of the paper using simple lines (—) consequently horizontal bonds will project above and below the plane. COOH CH3 Br H Br H3C COOH H When Br above the plane When H above the plane Br CH3 COOH H
- 23. Conversion of FlyingWedge into Fischer Projection The molecule is rotated (in the vertical plane) in such a way that the bonds shown in the plane of the paper go away from the viewer and are vertical. Rotate the model in vertical plane so that C—COOH and C—CH 3 go away from the viewer H CH3 COOH Br Br CH3 COOH H
- 24.