![]() ![]() ![]() How to draw the enantiomer and a diastereomer of a Fischer projectionįischer projections make it easy to draw different stereoisomers. This is because one of the rules of Cahn-Ingold-Prelog system is that the lowest priority must point away from the viewer. However, this is where you need to remember that the horizontal groups (Cl and H) are pointing towards you, therefore, the configuration must be switched from R to S. The arrow goes clockwise which indicates R configuration. Next, draw the arrow going from priority 1-2-3: In this molecule, for example, we need to assign the priorities of the groups on the chiral center based on the atomic numbers: To determine the absolute configuration of chirality centers in a Fischer projection, we need to follow the same steps as we do for any other representation such as Bond-line or Newman, according to the Cahn-Ingold-Prelog rules. ![]() In this case, as well, the horizontal groups have to be pointing towards you.ĭetermining the absolute configuration (R, S) of Fischer projections Or, you look at the Fischer projection like you are in the gym and need to grab the molecule. Well, you can remember that Fischer projections like you and they are coming to give you a hug with open arms: So, how do you remember which ones are pointing towards you? This, however, is not the Fischer projection yet, since, remember, we said the main idea was to avoid showing wedge and dash lines yet being able to convey absolute configuration of the chirality centers ( R, S).įor this, we are going to draw the molecule and simply show all the bonds with plane solid lines, keeping in mind that the horizontal groups are pointing towards you and the ones on the vertical line are pointing away from you: There are two wedge and two dash lines which may look strange to you since we always have one of each and then the two solid lines but it is okay-it all depends on the direction we are looking at the molecule. We will show the ones on the sides with wedge lines and the others with dashed lines: If you look at the molecule from the top, you will see the following representation where the two groups on the side are pointing towards and the ones on the top and on the bottom are pointing away from you. Remember, numbering carbons will always be helpful no matter what you need to do with an organic structure. Suppose you have this compound with one chirality center:īefore getting to drawing its Fischer projection, lets number the carbons in any order (no IUPAC rules needed). This is especially applicable and used mostly for drawing sugars. They were initially proposed by Emil Fischer for making it easier to draw the structures of compounds containing multiple chirality centers with the main idea of not having to draw the wedge and dash lines for every single chiral center. Fischer projections are just another way of drawing compounds contacting chirality centers. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |