An EASY Way to Convert Fischer Projections into Bond Line Structures and Back

[@VictortheOrganicChemistryTutor]

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[@Alexis-qz9ci]

omg thank you for this, Fischer projections have been kicking my butt. You do an excellent job of explaining all of these topics. I've been recommending your channel to everyone in my orgo 1 class

[@VictortheOrganicChemistryTutor]

Aww, thanks! Fischer projections are a pain, but you got this! Glad my videos are helping you out-keep spreading the word, I really appreciate it!!!

[@peybak]

"We all float down here." That's a real neat trick.

[@andreaorellana264]

hi in example 2 (starting at 13:00), I was wondering why carbon 2 is in the R configuration. I put the aldehyde group as the first priority, then the alcohol as the second priority and then the group to the right as the third priority. I keep getting the S configuration, so I just wanted some clarification since its in the R configuration, thank you for your help!!

[@VictortheOrganicChemistryTutor]

How do we assign priorities? 😉 We gotta analyze the structure atom-by-atom. The -OH group has higher priority than the aldehyde b/c the very first atom connected to our chiral carbon is O from the alcohol vs C from the aldehyde, once you have your first difference, the rest of the group is irrelevant.

[@akrxmm]

the floating trick is such a game changer, thank u bro

[@VictortheOrganicChemistryTutor]

That's how I do it myself 😆

[@hemersoncarvalho8178]

wow, best projection fischer class ever!!!

[@VictortheOrganicChemistryTutor]

Thanks for the love! I'm thrilled you enjoyed the video.

[@HasanAl-Mosuli]

Hello, (at 6:10) Shouldn't carbon #2 have the S stereodescriptor? My thought process behind this is that: 1- OH group has the highest priority, 2- Carbon #1 with the aldehyde has the second highest priority, and 3- Carbon #3 has the third priority. Drawing the Newman projection, OH is on the top right, C #1, is on the top left, and C #3 is on the bottom, with hydrogen on the back. Am I doing this right 😅

[@VictortheOrganicChemistryTutor]

You forgot that the lowest priority needs to look away from us, so you have to rotate the molecule before you can assign the stereodescriptors.

[@andreypacik4558]

Thanks a lot!

[@SnuffIt]

5:53 could I draw the alcohol OH with a wedge line not down but up? So both alcohol groups are up with wedge lines?

[@VictortheOrganicChemistryTutor]

No you cannot do that, that would make no sense. I have a tutorial with do’s and don’t’s of the dash and wedge representations among other things on the site, you should check it out.

[@TalkswithS]

Does my direction when it comes to numbering of my bond notation matter since you started from the left , am I able to start numbering from my right as well

[@VictortheOrganicChemistryTutor]

It doesn't matter. Just make sure you're either "floating" in the appropriate direction or doing your R/S stereodescriptors correctly if you like that way better.

[@andimartinez3086]

Carbon 2 aand 5 are the same, so why is carbon 2 represented as dashed and carbon 5 represented as wedged; is it because one is facing up and the other is down?

[@VictortheOrganicChemistryTutor]

I assume you’re referring to the glucose example? Yes, they are twisted in space in a different direction, so they will end up looking at different directions when we convert them. That’s why I introduced multiple different ways how you can double check your group orientations including the R/S stereodescriptors which would be the most straightforward way if you’re having a hard time imagining the molecule in 3D.

[@amirkazemi5980]

Great video! Does the R/S method always work?

[@VictortheOrganicChemistryTutor]

For as long as you're assigning your R/S stereodescriptors correctly, yes, it does.

[@justdoesntmakesense]

Sorry to bother you, but I was hoping you could help clear something up for me. At 11min exactly, you label carbon 3 as 'S' but I do not understand why. I watched your very helpful R and S assigning video. And from what I can understand, The OH is priority 1, and H is priority 4, but then there are two carbon chains to comare. The upward facing Carbon (carbon 2) has H and OH as does the bottom facing (carbon 4). So we move another carbon along. So I am now comparing Carbon 1 to Carbon 5. Carbon 1 has a real O, a phantom O and an H. Carbon 5 has an OH and an H. So surely Carbon 1 is the higher priority, making the upwards carbon chain Priority 2, and downwards priority 4. Looking at the fischer, this means we have Priority 1 on the left, 2 on the top, 4 on the right and 3 on the bottom. How does this become S? We do not know the wedges and dashes yet, as that is the point. I feel that I am missing something... is this covered in another video I could watch? Any assistance much appreciated!

[@VictortheOrganicChemistryTutor]

In the Fischer, all vertical lines are dashes and horizontal lines are wedges. I've mentioned that at the beginning of the video. It's always like that. Now, if you follow the priorities carefully, -OH is 1, the top group is 2, the bottom is 3, the hydrogen is 4, just like you did (I assume there's a typo in your initial message in the middle when you said the one on the bottom is 4). Hydrogen and -OH are on the wedges, top and bottom are on the dashes. So, once you rotate your chiral carbon in space to make sure the lowest priority looks away (or do the double-flip trick that I teach in the R/S video), you'll get the S stereoconfiguration here.

[@justdoesntmakesense]

@@VictortheOrganicChemistryTutor sorry it was late at night here, yes that was a typo. Thanks for getting back to me! I forgot about the bow ties and was over focused on the thought that I had the priorities wrong. But I didn't I just had the 3D bits wrong. Thanks so much for clearing that up. I'm loving your videos they are amazing!!!