The beta diastereomer of the cyclic form of glucose is shown below in three different depictions, with the Haworth projection in the middle.
An alternative way to represent stereochemistry is the Fischer Projection, which was first used by the German chemist Emil Fischer. So this line right here means a bond to an aldehyde. So right here, let's draw in our carbon. To find the enantiomer of a molecule drawn as a Fischer projection, simply exchange the right and left horizontal bonds.
In a Fischer projection, the carbon atoms of a sugar molecule are connected vertically by solid lines, while carbon-oxygen and carbon-hydrogen bonds are shown horizontally. So we represent that with a wedge. On a Fischer projection, the penultimate next-to-last carbon of D sugars are depicted with hydrogen on the left and hydroxyl on the right.
If a Fischer projection of this type can be divided into two halves that are mirror images than the molecule may be identified as a meso isomer. The cross image to the right of the arrow is a Fischer projection. So here's our aldehyde going down into the right, and then this would be your left side.
I like to imagine this carbon as being in the plane of the page. This is the way that I usually use. So we write oxygen, oxygen, hydrogen. When creating a Fischer projection for a carbohydrate with more than three carbons, each down carbon that would project away from you as viewed from the top in the Zig-Zag model must be turned around and oriented as towards your view.
So now we would represent that with a dash. The hydrogen is now going away from us in space. I'll show you the two that I like to use.
So let's assign priority to our four groups. D-glucose chain All nonterminal bonds are depicted as horizontal or vertical lines. The OH here is coming out at us in space. Instead of using the ethane shown in Figure A and B, we will start with a methane.
And so the only way to do that would be to put our eye right here and to stare at our chiral center this way.
L sugars will be shown with the hydrogen on the right and the hydroxyl on the left. So let me put an OH here. That means a bond that's coming out of the page. And then we have our CH2OH going down and to the left. The Fischer Projection represents every stereocenter as a cross. Same thing with this vertical line here to the CH2OH.
To show both conformation and stereochemistry, you must draw the ring in the chair form, as in structure C above.The Fischer Projections allow us to represent 3D molecular structures in a 2D environment without changing their properties and/or structural integrity.
Fischer Projections Introduction to Fischer Projections The wedge and dash representations of stereochemistry can often become cumbersome, especially for large molecules which contain a. A Fischer projection or Fischer projection formula is a convention used to depict a stereoformula in two dimension To determine the absolute configuration of a chiral center in a Fisher projection, use the following two-step procedure.
However, with care, they can be applied to Fischer projections containing any number of chiral centers. Fischer projections are convenient for comparing the stereochemistries of molecules that have many chiral centers.
But these projections have their own sets. Fischer Projections. Fischer Projections are abbreviated structural forms that allow one to convey valuable stereochemical information to a chemist (or biochemist) without them having to draw a more detailed 3D structural representation of the molecule.
Fischer projections are just another way of drawing compounds contacting chirality centers. They are used for drawing molecules containing multiple chirality centers with the main idea of not having to draw the wedge and dash lines for every single chiral center.Download