Fischer Projection Stereochemistry R S Chirality for one or more chiral centers

[@studygroupprepusmle]

Thank you, this was very clear and straight to the point. I am currently studying for the MCAT and I found this to be excellent refresher.

[@Leah4sciMCAT]

Glad to help! When are you testing?

[@prokokex1365]

I was so obsessed with making even exchanges in fischer projections And left all the questions in my tests which had more than one chiral centers with least priority group not on base .... But now that short trick is gonna help me a lot .. Thanks a lot.

[@Leah4sciMCAT]

Glad I could help!

[@AquaticLogic]

This method is clearer and simpler than any other I have seen, which is easy to understand, and saves time. What more could you want? Thanks so much for your investment in these videos.

[@Leah4sciMCAT]

Oh wow, thanks for your kind words, I'm so glad to have helped!

[@csivila]

You clarified it so well and i appreciate your organized style of teaching. Excellent work

[@Leah4sciMCAT]

+christopher sivila Thank you! glad to help

[@dominogirl09]

This is the best explanation that I have ever heard! You're awesome! Million thanks for saving me before my exam

[@Leah4sciMCAT]

You are so welcome! So glad it helped you on your exam!

[@vidurangasathsarana7338]

Thank you madam. I understood it clearly. So are there any video regarding mechanisms of reactions of organic compounds?

[@Leah4sciMCAT]

I have an entire channel on that leah4sci.com/youtube

[@isaacmolina5500]

One question. In the first example (2:40 minutes) why did you put 3 oxygens when there are only 2?

[@Leah4sciMCAT]

This has to do with the Cahn-Ingold-Prelog rules for prioritizing groups. Pi bonds count as 2. I explain this in my Cahn-Ingold-Prelog video in this series: Leah4sci.com/chirality

[@queennmo]

@@Leah4sciMCAT sis you dont get the question...like why are there 3 oxygens instead of 2.

[@alisonstarr]

@@Leah4sciMCAT Hi Leah, I really love your videos. I have the same question as above. I've watched all the chirality videos but I'm still unsure. Do you have an easy lesson to explain it? I've watched the Sigma/Pi video but I'm more confused.

[@chavakavitha1368]

@@alisonstarr it is based on CIP rule Search for this rule in KZbin if you don't understand

[@alisonstarr]

@@chavakavitha1368 Thank you, another very helpful lesson. But... I still don't understand where the third O came from. Also why a single bond on the third O?

[@DrReagge]

What if of the 4 substitutes two of them are CH2, in a ring for example, how do I know if it spins R or S??

[@Leah4sciMCAT]

+DrReagge if they are EXACTLY the same then the carbon will be achiral. See leah4sci.com/chirality

[@DrReagge]

Thanks a lot!

[@ayeshaarslan1381]

I am 9 years late but could you please explain how you got the lower part of the atom's configuration to be R and then S because it was going in the left direction so wouldn't it be S ? i got it

[@Leah4sciMCAT]

When we traced a path from 1 to 2 to 3, we initially got R. Then, we have to remember that group 4 must be towards the back of the molecule in order to assign configuration. So we flip the configuration from R to S to accommodate for Hydrogen being in the front of the molecule. You can learn more about the Swap Method by visiting my full Chirality and Stereochemistry series at Leah4sci.com/Chirality

[@briannafraser6084]

6:52, but the direction the arrow is in is going to the left, so that's S, but you have to switch it, and when you switch it, it'll be R. So how did she get the apparent configuration as R and the real configuration as S? NVM. I got it.

[@Leah4sciMCAT]

Glad you figured it out!

[@ayeshaarslan1381]

wait how did you figure it out, I'm confused with the exact same thing

[@leorachapman679]

Would this work if you had three stereocentres or more?

[@Leah4sciMCAT]

+Leora Chapman of course! See the 6-carbon sugar on the Fischer quiz

[@shimonyehudaommatyar8834]

Hello! First off, your lectures have helped immensely. Thank you! Quick question - when looking at fisher projections, aren't you supposed to do the opposite of the R and S? Like if it is S (assuming H is on the dashed line) then it should really be R? Thanks!

[@Leah4sciMCAT]

If H is right or left then you have to apply the rule for 'group #4 forward' so yes.

[@Q-Bits8]

So what's the difference between R,S and D,L?

[@Leah4sciMCAT]

R and S is used to rank based on atoms as drawn on paper, D and L has to do with the Fischer Projection structure initially discovered by how one specific set of enantiomers each rotated plane polarized light

[@Q-Bits8]

@@Leah4sciMCAT bro I have doctors degree now, you are 7 years too late. Thanks anyways!

[@CheeseBallBouncers]

Thanks so much!

[@Leah4sciMCAT]

You're very welcome!

[@AndrewHeaton_]

unshaired electron pairs is a lower priority than hydrogen

[@Leah4sciMCAT]

+Andrew Heaton correct! My examples only compare atoms though

[@zetrixcsgo]

❤❤THANKS

[@Leah4sciMCAT]

You're very welcome