Amino Acid Stereochemistry R and S vs D and L Configuration

leah4sci.com/a... presents: Amino Acid Stereochemistry finding R and S or D and L on Fischer Projections and linear molecules.
📺Watch Next: Amino Acid Stereochemistry R&S vs D&L • Amino Acid Stereochemi...
Is your MCAT just around the corner? Grab a free copy of my ebook "MCAT Exam Strategy - A 6 Week Guide To Crushing The MCAT" at leah4sci.com/M...
This is video 4 in the MCAT amino acids tutorial video series. How to determine if amino acids are R/S or D/L from linear and Fischer forms and how to quickly convert between them.
Referenced in this video:
Chirality tutorial series: leah4sci.com/c...
Catch this entire video series along with my amino acid cheat sheet, tutorials and practice quiz on my website:
leah4sci.com/a...
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[@vivekkrishna340]

This video should be obligatory viewing in any organic chemistry/biochemistry class that teaches L vs D orientation. Amazing

[@Leah4sciMCAT]

Haha glad it helped

[@aref6561]

Definitely the best

[@maggiephillips3579]

Four years later and this video is still helping students! Thank you for helping me with Fischer projections of amino acids, something I was really struggling with!

[@Leah4sciMCAT]

You're very welcome, glad it helped!

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I never comment on public place but you so much worth a complement. You are an amazing teacher.

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Compliment*

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[@persistentconsistency]

Paused my biochem reading for lecture to learn a bit more about L & D since I never saw this in O-chem. Appreciate the thorough lesson!

[@Leah4sciMCAT]

So glad I could help!

[@Leah4sciMCAT]

My prof never went into this either, glad the video helped

[@AlanPhasavath]

I like the detail you went into they usually don’t teach this into depth, they just scratch the surface and move on. Thanks for the vid it helps even 5 years later 👍

[@Leah4sciMCAT]

Glad it was helpful!

[@ACDBunnie]

6:32-7:43 Literally, in less than a minute and a half you taught me such an easy way to tell apart an L and D Fischer projection. I thought it would take forever for me to learn how to tell them apart! Thanks again!

[@Leah4sciMCAT]

Oh wow! So glad I helped you understand it so quickly!

[@TheCelticBomb]

I love you so much. You are so unbelievably helpful. Not only do you explain things super well, and make everything really clear, but you also maintain an animated voice which makes all the difference. The inflections and "enthusiasm" in your speech (whether feigned or genuine) really helps to pay attention and pick up the information. You are a godsend.

[@Leah4sciMCAT]

Thank you very much! My goal is to always make it as fun as possible :)

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good luck to all of those studying for the MCAT

[@Leah4sciMCAT]

Yes!

[@Leah4sciMCAT]

💯

[@fujoshipeanut5074]

This is perfect, thank you! This is the only resource I've found that explains how to determine L and D

[@Leah4sciMCAT]

Happy to help!

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This woman got me a 95% in organic chemistry 2 , and now she's carrying me in biochemistry

[@Leah4sciMCAT]

Awesome! Glad to help!

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[@Leah4sciMCAT]

You're very welcome!

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[@Leah4sciMCAT]

You're welcome, hopefully no more panicking!

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[@Leah4sciMCAT]

You're very welcome!

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[@Leah4sciMCAT]

I'm so glad to hear that you understand!

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I am from india and i really loved and actually just grasped everything u said in minutes rather then spending hours with books and then the books made sense thanks ma'am it was really very helpful

[@Leah4sciMCAT]

Glad to help! :)

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This was so good! It really helped explaining what my professors or book could't, right before my exam. I quite enjoy the amount of examples.

[@Leah4sciMCAT]

I'm glad that it helped!

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[@Leah4sciMCAT]

oh wow! good to know that! Congratulations! Thank you for the nice feedback. Always glad to help :).

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Oh wow congrats on acing orgo! Hope you aced your MCAT as well

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[@Leah4sciMCAT]

You're welcome! :)

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YAY!!! So happy this helped you get a clear grasp on it!

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[@Leah4sciMCAT]

Glad I could help!

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i'm from Argentina and i couldn't find this exactly explication in spanish, i'm so glad to have found your video thank you very much

[@Leah4sciMCAT]

You're very welcome!

[@Leah4sciMCAT]

Glad you were able to understand in english

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Whenever i feel complications in understanding chemistry concept i refer MCAT. You are great ma'am❤ I love the way you crack the hardest topics in the most simplest manner💐 Kudos to you ma'am🙏

[@Leah4sciMCAT]

Aww, thanks for that! I'm glad my resources help you to understand!

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[@Leah4sciMCAT]

Thank you very much. Glad you enjoyed it

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[@Leah4sciMCAT]

You're welcome 😊

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[@Leah4sciMCAT]

You're very welcome and thank you for your kind words. A lot of work goes into this, but I love doing it!

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[@Leah4sciMCAT]

You are very much welcome! Glad to have helped and thanks for sharing the video :)

[@Leah4sciMCAT]

You're very welcome! Hope watching it a second time helped it all click

[@kavyakothalanka5242]

awesome!!!! i just lost my stress on covering this part of aminoacids. thankuuu soo muchhh!!!

[@Leah4sciMCAT]

Yay! I'm so happy to hear that, and you are very welcome!

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so glad this video helped reduce your stress

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[@Leah4sciMCAT]

Thanks!

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[@Leah4sciMCAT]

You are very welcome; so glad it was helpful!

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Thank you so much for making this video! You have helped me understand this topic more than 3 years of university could🥴

[@Leah4sciMCAT]

You're welcome! Glad it was helpful!:)

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[@Leah4sciMCAT]

Glad I could help!

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So glad it helps!

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Better late than never? glad it helped

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Thank you for your kind words!

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Good video for quick exam prep but not very much for learning chemistry tbh. The principle and logic behind this chemistry are not explained (which is not required if you just want to pass exams especially for premeds). But I appreciated the effort. Thanks.

[@Leah4sciMCAT]

You're welcome

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[@Leah4sciMCAT]

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Always glad to help!

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Glad you enjoyed it!

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[@Leah4sciMCAT]

You are so welcome!

[@nicolasbaroni9053]

Can you reiterate how exactly you know when to change the direction of our loop when connecting 1,2&3? Is It only when the hydrogen is coming out of the paper?

[@Leah4sciMCAT]

Go back to this series: leah4sci.com/chirality/

[@Leah4sciMCAT]

I cover this extensively here: leah4sci.com/chirality

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[@Leah4sciMCAT]

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[@Leah4sciMCAT]

You're very welcome

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Wow, thanks for the offer, but I'd rather you not have to do that :)

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Glad it finally clicked :)

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[@Leah4sciMCAT]

Thank you!

[@rajithadhanu4181]

Thank you for your videos. You are a best teacher ever.I have followed your materials to improve my knowledge. I have a question in Stereochemistry. There are some few videos in youtube that they mention III ry amine have a chiral center. There is a problem because when I do the ACS questions they not accepting it as a correct answer. please give me an answer If you have a free time to attend with this matter. Thank you

[@Leah4sciMCAT]

I'm sorry, but I don't offer tutoring through KZbin comments. For help with questions like this and more, I recommend joining the MCAT Study Hall. For more details visit join.mcatstudyhall.com/ or contact me through my website leah4sci.com/contact/

[@Leah4sciMCAT]

This is a tricky question, Tertiary amines are technically chiral due to their shape, but the 4th group is a lone pair which is constantly inverting and so you won't ever have just R or S. Quaternary amines on the other hand can have 4 unique subs for a proper chiral center

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Very well explained! Save me so much time!

[@Leah4sciMCAT]

Glad it helped!

[@Leah4sciMCAT]

You're very welcome!

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[@Leah4sciMCAT]

You're welcome! Glad you got it :)

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Too easy is hopefully a good thing

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[@Leah4sciMCAT]

You're welcome! Glad I could help

[@Leah4sciMCAT]

You're very welcome and thank you :)

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This video is really amazing! And excellent explanation..

[@Leah4sciMCAT]

Glad you liked it!

[@Leah4sciMCAT]

Thank you

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Great explanation, great explainer.

[@Leah4sciMCAT]

Thank you :)

[@faithomosor1744]

I think you meant to say that oxygen has more priority than nitrogen since we are going by atomic numbers not the other way around. So the carboxylic group will be number 1 and the ammonia will be number 2.

[@Leah4sciMCAT]

The carboxylic group has a carbon (not an oxygen) directly attached to the chiral center, and carbon is lower in priority than the nitrogen in the amine.

[@Leah4sciMCAT]

Oxygen outranks Nitrogen, however in a carbonyl group it's the Carbon we're comparing to Nitrogen and so the amine outranks the carboxylic acid

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you're an amazing teacher!!!

[@Leah4sciMCAT]

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Thank you

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Thank you :)

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[@Leah4sciMCAT]

You're very welcome!

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Very clear explanation..thank you!

[@Leah4sciMCAT]

You are welcome!

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You're very welcome

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this is so helpful, wish I had found the video earlier

[@Leah4sciMCAT]

Glad it was helpful!

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You're very welcome! Better late than never, right?

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Thank you so much this was great Leah

[@Leah4sciMCAT]

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[@Leah4sciMCAT]

You're very welcome

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[@Leah4sciMCAT]

You are so welcome!

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You're very welcome

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A very useful video!

[@Leah4sciMCAT]

Glad you liked it!

[@TheACLP]

for the S-Aspartate question at 21:15 if we used the guess and check method, even if we place the +NH3 on the right side for D configuration it would still be an S, so no matter the L or D conformation it will both be S, so how can you use this method if you're trying to compare the S configuration of the line and wedge to both the L and D conformation if both are S?

[@Leah4sciMCAT]

I'm confused by your question. If we swapped the NH3 group with the Hydrogen and had the NH3 on the right side of the Fischer, we would have an R configuration to the stereocenter. Making a swap like this changes the configuration of the chiral center. For help with questions like this and more, I recommend joining the MCAT Study Hall. For more details, visit join.mcatstudyhall.com/ or contact me through my website leah4sci.com/contact/

[@GreenOnionBrother]

Thanks, you are a life saver! Now I have to move on and deal with E/Z, though. -.-

[@Leah4sciMCAT]

Glad I could help! Is this what you are referring to? leah4sci.com/cis-trans-and-e-z-geometric-isomers/

[@GreenOnionBrother]

Ah, yeah, exactly! Thank you :D

[@Leah4sciMCAT]

You're very welcome! I cover that in detail as well

[@BattleHaven1185]

Here I am studying for my 2nd biochem test and this is the first time I'm learning R & S aren't the same as D & L? my professor literally told us that they were - that L was R and D was S. Gotta love paying thousands of dollars to be given wrong infomation D:

[@Leah4sciMCAT]

Ouch! Sorry to hear that!

[@Leah4sciMCAT]

Oh wow, yeah my biochem professor also tripped up on R/S basics, we had to correct him

[@garthswaney5439]

Well done explanation!

[@Leah4sciMCAT]

Glad it was helpful!

[@Leah4sciMCAT]

thank you

[@jacquelineleiman250]

Splendid video!

[@Leah4sciMCAT]

Glad you enjoyed it!

[@ajinkyajadhav3424]

Maam my question is, in last ex.of aspartate you have shown that hydrogen atom in front to the observer but as the (Fisher projection formula) but a/c to Fisher projection rule it should be at left side of horizontal bond as it is back side of the plane, how it is possible

[@Leah4sciMCAT]

I'm sorry, but I don't offer tutoring through KZbin comments. For help with this and more I recommend joining the MCAT study hall. Full details: join.mcatstudyhall.com

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I'm glad you like it!

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[@Leah4sciMCAT]

Thank you for your kind words!

[@Leah4sciMCAT]

You're very welcome

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[@Leah4sciMCAT]

You're welcome!!

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You're welcome!

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[@Leah4sciMCAT]

Thanks! I'll take the compliment. :)

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Thank you SO much!

[@Leah4sciMCAT]

You're very welcome!

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[@Leah4sciMCAT]

You're very welcome

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[@Leah4sciMCAT]

Thank you

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Thank you for the kind words and for subscribing

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Thanks ma'am

[@Leah4sciMCAT]

You're welcome! :)

[@Leah4sciMCAT]

you're welcome

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This was an amazing video! Thank you so much!!

[@Leah4sciMCAT]

You're so welcome!

[@Leah4sciMCAT]

You're very welcome

[@alexcooper-hohn4259]

Can you explain how you know the H is coming "forward" even though it just appears to be in the plane?

[@Leah4sciMCAT]

If speaking about the Fischer projection (looks like a flat cross molecule), then groups on the horizontal line are coming out of the page, by convention. While groups on the vertical line are going into the page, by convention. For more about Fischer projections, what they mean and how to draw them, make sure to see my free tutorial series at Leah4sci.com/Fischer

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That was just WOW

[@Leah4sciMCAT]

Thanks!

[@Leah4sciMCAT]

Thank you :)

[@ayleenc.205]

Can somebody explain why she does the second swap (during 10:32) ? I know she said to "maintain the chirality," but can somebody explain that please! Thank you:)

[@Leah4sciMCAT]

At this point in the video, we are trying to transform the Fischer projection of R-alanine into proper form where all carbons would be along the vertical backbone of the molecule. That means we need to swap our carboxyl group to the top-most position, so that it falls along the vertical. When we make that swap, we also need to swap two other groups in order to maintain an R configuration at the chiral center. If we didn't make a second swap, we would then have the S configuration of alanine. Which is a different stereoisomer of our original molecule.

[@hookem3768]

Why did you skip the two hydrogens of the CH2-SH group? Wouldn't the Carboxyl group have higher priority due to the amount of bonds to oxygen?

[@Leah4sciMCAT]

Both Sulfur and Oxygen are directly bonded to a carbon on the chiral center. If Sulfur outranks Oxygen with its atomic number, the number of bonds to Oxygen are irrelevant. Sulfur is the winner and would be higher priority.

[@Farhan-co9he]

you are great..thanks

[@Leah4sciMCAT]

Thanks, and you're welcome!

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You are the best ... thank you so much

[@Leah4sciMCAT]

You're very welcome!

[@Leah4sciMCAT]

You're very welcome

[@بثينةبوتي-س8ن]

Thanks

[@Leah4sciMCAT]

You're welcome!

[@hitensingh6629]

I came looking for non coded Amino Acids. But I don’t think this is about that. But u could help me. So the line is - amino acids having D-Configuration or which aren’t alpha amino acids are Non coded. What does this D configuration mean ?

[@Leah4sciMCAT]

To be non-coded simply means that the amino acid was not coded for by the DNA sequence. It must have been synthesized by some other process, outside of the body. All of the amino acids derived from natural (human-made) proteins are of the L configuration. D-amino acids are found in nature.

[@bittukumarjha5244]

Thanks ❤

[@Leah4sciMCAT]

you're welcome

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Thanks a looooot!!!!

[@Leah4sciMCAT]

You're very welcome!

[@unicorn9957]

You go girl, this is amazing! Thank you!

[@Leah4sciMCAT]

Glad to help! You're welcome :)

[@Leah4sciMCAT]

You're very welcome

[@michelleprince7832]

Very very helpful!

[@Leah4sciMCAT]

thank you!

[@Leah4sciMCAT]

Thank you

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Thanks a lot.

[@Leah4sciMCAT]

you're very welcome

[@benphung4315]

Love this video! I love how you encourage understanding, not just memorization. I struggled with this topic a lot but you made it understandable! Thank you!

[@Leah4sciMCAT]

You're so welcome! I'm glad it was helpful!

[@Leah4sciMCAT]

Thank you! and absolutely YES to understanding before you attempt to memorize. If you memorize you forget, and then what? If you understand you can reason your way through it because of what you truly GET

[@winsenken]

So if I change the stereochemistry of specific amino acid from R to S or S to R, the the L and D configuration will also swap automatically right??

[@Leah4sciMCAT]

I'm sorry, but I don't offer tutoring through KZbin comments. For help with this and more, I recommend joining the MCAT study hall. Full details: join.mcatstudyhall.com/

[@Leah4sciMCAT]

exactly, yes

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if I could give you a hug I so would. thank you!!!!!!!!!!!!!!

[@Leah4sciMCAT]

Virtual hug accepted and reciprocated :)

[@saiei]

Thank you soo much

[@Leah4sciMCAT]

You're welcome!