FISCHER AND NEWMAN PROJECTIONS

In 1891,Emil fischer devised a method of representing the 3D structures of
molecules in 2D Structures on a plane (Paper) by convention, horizontal line
represent bonds projecting from the plane of paper towards the observer and
vertical line represent away from the observer

1. TUMKUR UNIVERSITY DEPARTMENT OF STUDIES AND RESEARCH IN ORGANIC CHEMISTRY  Seminar on FISCHER AND NEWMAN PROJECTIONS Presented By Rakshitha S (P11AZ22S104037) I MSC, I Sem Department of studies and research in Organic Chemistry Tumkur University, Tumkur . . 1

2. CONTENTS INTRODUCTION DEFINITION AND RULES OF FISCHER PROJECTION ADVANTAGES AND DISADVANTAGES SOME STEREOCHEMISTRY ASPECTS DEFINITION AND RULES OF NEWMEN PROJECTION ADVANTAGES CONCLUSION REFERENCES 2

3. INTRODUCTION   Projection formulas: The molecules can be visualized and represented on a paper by several projection formulae 1.Wedge-dash projection 2.Newman projection 3.Fischer projection 4.Sawhorse projection 5.Haworth projection 3

4. Rules for showing the arrangement around the asymmetric carbon In this representation, bonds are solid lines, The bonds are placed vertical and horizontal to each other Fischer projection: In 1891,Emil fischer devised a method of representing the 3D structures of molecules in 2D Structures on a plane (Paper) by convention, horizontal line represent bonds projecting from the plane of paper towards the observer and vertical line represent away from the observer . 4

5. The intersection of vertical and horizontal line is called stereocenter Maximum number of the carbon chain is present in vertical line(Longest carbon chain) Horizontal line is coming out of the plane of the paper(towards the observer) and vertical line is going back behind the plane of paper( away from the observer) In fischer representation most oxidized carbon atom is placed on top of the vertical line Ex:1 5

6. 2. Advantages To represent chairal molecule It is used to represent molecules and compounds , especially structure of monosaccharides and amino acids To differentiate between pair of enantiomers To differentiate between D and L molecules 6

7. Disadvantages These projections can be rotated only in certain specified way Fischer projection represent only in the eclipsed form In compound more than one stereocenters , fischer projection implies an eclipsing relationship of group attached to stereocenter but staggered is more stable than eclipsed Some stereochemical aspects when rotate the fischer projection In 180 degree rotation in the plane gives the same stereo chemistry It allowed and identical 7

8. I n 90 degree rotation in the plane gives the inverted stereochemistry It is not allowed and not identical Exchanging any two position gives the inverted stereochemistry 8

9. Newman projection In 1952,Newman devised a way to draw chemical conformational and views a carbon-carbon chemical Bond from front carbon is represented as dot and back carbon is represented as circle. It easy to assess the dihedral Angle between two bonds one at each carbon atom Rules for representing the molecules in newman projections In this representation molecule is viewed along the bond joining the two carbon atoms The front carbon shown by three solid lines that is “Y” 9

10. The back carbon is shown by a circle with a three bonds pointing out from it Combining the front and back carbon results in the eclipsed newman projection which on rotating through 180 degree results to get staggered newman projection 10

11. The three groups on the carbon atoms are shown as being to bonded to dot or circle by an angel 120 degree to each other In newman projection formula all the parallel bonds are eclipsed But in case of all anti parallel bonds are staggered The dihedral angel in eclipsed is zero degree The dihedral angel in staggered is 180 degree or 60 degree Example 1: Ethane 11

12. Advantages Newman projection is that they are easy to draw and clearly show the relationship among substituents on the different carbon atom 12

13. CONCLUSION Fischer projection formula are used to represent the molecules from the 3D to 2D To the chirality of a molecule and distinguish between o pair of enantiomers Newman projection is useful to visualizes the conformation of a chemical bond from front to back 13

14. REFERENCES 1.Stereochemistry conformation and mechanism(8 th edition) by P S kalsi 2.Stereochemistry by Alex v , Ramani,Leo A,Stanley 14

15. THANK YOU