Fischer Projections!!!

[yalla22]

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I am totally confused about fischer projections-what is this business about 180 degrees in the plane?! I keep turning the thing to compare chirality but im totally wrong..like you cant flip it but so how is that different from turning it 180 in the plane of the paper? was anyone else confused about this and see where im coming from? i think its one of those things that once you see you're like "oooh"..
please help!!🙂

 

[musiclink213]

get models. this confused me too, until i got models. then, put a different color ball on the end of each b0ond to indicate priority. if your prof is nice like mine, she;ll let you use them on the test. i use #1 to be red, then blue, than white, and green is the lowest priority. once u compare the fisher projections with the model, than you can turn them any way you want.

the reason you can only turn them 180 in the plane is cause of the way they stick out. you have to remember that the horizantal stick out of the plane and the vertical go behind the plane. if you flip them over, than even if you keep the groups in the same 2-D area, they will be in diff. positions in the 3-D, the horizantal go behind the plane, and the vertical go out of hte plane, and then you get messed up.

hope this makes sense, and didn't confuse u too much, it's easier to explain when someone is explaining it in person. i also hope this is all factual info.

 

[DSM]

Think of a pin wheel with 3 blades, each pin wheel is on the opposite end of a stick. Each blade is a different color. Rotate each blade a third of the way around until each color has had a turn on top. Remember the pin wheel on the other end may or may not turn. That is a Fischer projection in it's simplest form.

Also get a really good model set. They really do help. You will be ooooooing and aaaaahhhhing before you know it!🙂

 

[chaeymaey]

I don't understand. When do we need to rotate Fisher projections?

 

[ATPase]

You may need to rotate them or switch pairs to determine whether two different Fischer projections represent the same configuration or if they are enantiomers.

That sounds confusing, but there's a really good explanation of Fischer projections in the Kaplan MCAT review book.

 

[Noeljan]

I would rotate Fishers to make comparisons between the two(ex are they enantiomers, diastereomers, identical, etc) You are trying to figure out relationships....Also are they superimposable=same Remember that horizontal is coming towards you and vertical is behind you. Thats what I do anyways. Use model kits, Use model kits!!!! It helps.......
Oops ATPase answered🙂

 

[yalla22]

okay guys i totally get it now!

 

[Hemichordate]

Sorry for bumping an old thread, but would the easiest way to determine if a number of fisher projections are equal, enantiomers, or diastereomers just be by determining the R/S configurations of each chiral carbon and comparing those between molecules?

 

[GoSpursGo]

Sorry, but the SDN forums are not an appropriate place to be asking for homework help. If this is a question pertaining to studying for the MCAT, you might want to ask your question in MCAT Discussions in the Study Questions Q and A subforum. This thread is now being closed.