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. In 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