Stereochemistry - A Simple Trick for Determining R and S
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- Опубликовано: 9 янв 2025
- Simple trick to figure R and S when number 4 substituent is not in the back.
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thank you sooo much! just saved 4 hours of sleep bc of this vid
You are so welcome!
Best trick is this: switch H with whatever is in the back ("wedged") then determine R/S. The "true" R/S will be the opposite of that.
+Master organic chemistry I have a question sir, I was taught that even number of rotations in a molecule doesn't affect it...but you made 3 rotations(in the longer method)....so does that change the optical activity of the original molecule?
Wouldn't the back be on a dash instead of on a wedge?
Please can you show an example of one where H is in the plane of the pledge. I read your comment below about it, but didn't quite understand.
You're saving my chemistry exam, thanks!
You are so welcome!
You are the best. All ur videos help so much, I dont know how to thank great tutors like you!!
Thanks! Upvotes and shares are always appreciated : - )
Jij! Bent echt heel lief :)
(you are really sweet ;)
dude you're the GOAT, literally made this concept so much easier. Thanks man!
Thank you!
what if it was in the side
Literally...very helpful. Thank you is a small word to say.
Glad it was helpful!
So so helpful! I wish I'd found your page sooner!
Samantha Kennett glad you found it helpful!
You deserve a medal seriously amazing!
Thank you!
Omg most useful Ochem video I have so far seen :) great job, thank youuu
Thank you!!!!!! This looks so much simpler now that I'm not under pressure to learn this! I'm still retaking my Chem 112 class to hopefully boost my GPA by bettering my Chem grade. I get this now! Yayay! I've struggled with Chem for a year now and am just now breaking through. Whew!
You are so welcome!
Thank you! But what if H is in the plane of the molecule? Is there like a more general approach to this trick?
You may find our membership useful, here's a short video it's only a few minutes. Hope this helps - bit.ly/2YctxPb
Man, I missed one day of class to have a wisdom tooth pulled and it gives me hours of trouble. You have saved me.
Hope you feel better with the tooth! Glad the video is helping with the missed class
you saved me! thank you soooo much
What if H is not in the front? What would you do if hydrogen was in the side position like where -CH3 and -Cl are in the example?
At that situation there's come two methods ,it depends on you whichever method you will find more convenient. Here I will discuss both .
(1)As we all know hydrogen atom has lowest in priority so we rotate the H-atom till it reaches to dashed line. After that ,we simply rotate arrow from high priority group to low priority group . If the movement of an arrow is towards
(a)clockwise direction=R
&for (b) anticlockwise direction =S
(2) Whatever H -atom be carried position we simply rotate the arrow from higher to lower priority group and hence we get either R or S. If H-atom is not at the dashed position then we have to reverse our previous nomenclature result.
he already answered to Kaustubh Tandon : Best trick is this: switch H with whatever is in the back ("wedged") then determine R/S. The "true" R/S will be the opposite of that.
This is so clear. Thank you
Wow thank you so much!! Bond rotations are so tricky you've helped so much
You're so welcome!
Thank you this helped me a lot, much appreciated!
You are so welcome!
Thank you so much for this! I was confused for hours and now I understand! :)
Glad it helped!
Could you please explain why Cl-C bond stayed the same during rotation?
Try imagining the C-Cl bond as the axis about which the molecule is rotated.
@@ddk1018 but how do you know when to keep one of them the same and which one?
@@anonanon-rc7ib in the case given in the video we have the H above the plane, and for determining whether the compound is R or S the group with the lowest priority (in this case, hydrogen) should be below the plane. So to do that we consider the C-Cl bond as an axis and we rotate the compound around it, so the C-H bond gets moved from above the plane to below the plane.
Again we only did this rotation because we wanted to take the H behind. We wouldn't have to do that if the lowest priority group is already below the plane
In brief, the bond which we select as the axis for the rotation of the compound remains the same
@@ddk1018 Thank you👍🏻🏆✨
Wow this was very helpful, I now know how to assign s and r configuration 🙏
Thank you so much! :) So you can really just redraw the skeleton of the bonds and rotate the substituents around until the lowest priority is in the back? That seems too good to be true lol.
You are so welcome!
Please answer whoever know!!
Will this trick work even if the number 4 atom is not wedged but rather on a line ( on the plane of paper?)
Usually i see people use this trick when the number 4 atom is on a wedge but what if it was on a straight planar line?
Thank you in advance!
Same doubt
Thanks a lot !!!
Very Helpful
What do we do if group 4 is not on a wedge or dash? I have my DAT in 2 weeks and need to know in case it pops up , thanks in advance!
I am taking the DAT in a year and a couple of months from now. How was it? I am really nervous to take it, how did you do on it?
@@mblackops2 hello! you're doing good by being ahead of the game and thinking of the DAT a year in advance. tbh, it wasn't too bad. Practice is key. It's dependent on which subjects you are stronger in. For example, I really suck at chem and math - the exam was mainly Orgo, gen chem, math, bio. So I had to study a ton / practice since math and chem are my weakest. Bio was not too bad since it was my strongest. I got an 18 on bio the first time. Study tools I reccommend : DAT Bootcamp (helps get the basis/foundations down for like every subject- this is where I based my study notes off of) --- DAT Booster - for the PAT (especially) and I think its closer to the DAT than any other study tool tbh ---last thing : DAT Destroyer for the math and sciences (mainly math) . I believe with these 3 you will do really well. also, try to maintain a good diet during. my major mistake studying for the first DAT I took was not exercising like usual - it made me more stressed. Give yourself time to breathe and good luck! let me know if you have any other q's!
@@Sarahh_ Thank you!! For the information, it’s really good to see what other people have to say about things I will have to do in the future. Makes you feel not alone and I appreciate that. And tbh I’m not thinking about it too much I just seen your comment on this video Becuz I have my first Orgo Exam tmrw and I was watching R/S configuration videos to help me 😂 May I ask did you get into Dental School? My sister is about to graduate college this semester but she’s taking a year off school after graduating to build her resume to apply at Medical school, it’s really a tough process
@@mblackops2 Orgo is not as bad as I thought it was when I was init undergrad! its actually just repetition. I wish I can go back and redo those classes to get better grades cause I took gen chem's 1 and 2, Orgo lab, Orgo 1 and 2 in my university and it was harsh. studying them again for the DAT made life easier , and things clicked (that didn't previously) you will do great on ur exam iA! actually, no I have the chance to get in now, but I decided to not continue my dental journey after working in it for 1 year - hands on experience is much diff than just studying it , so I think I actually saved myself the hassle in the long run (even though I wasted a lot of money and time for the exam :(
Thx bro it it's still useful ❤
This is awesome. I get it now
amazing, thank you so much!
That was really great
thanks a lot❤
Thanks , it was really helpful 😃
Glad it helped!
this helped me a lot :)
The trick is very good sir... Hats off... :)
this is very helpful!! thanks!
You are so welcome!
Neat trick....thanx!
You're welcome!
This is the best 🙈🙈
Thank you!
I love your videos, i would fail my organic chemistry exam if it wasn't for you!. THANK YOU!!
Thank you! You are so welcome!
really helpful!!! thank you!!
You are so welcome!
You are amazing! Thank you.
we trace the line based on what? if it is 1,2,3,4 in order then it's R?
Great video thanks a looooooooooot.🖤
thank you!!
You're welcome!
What if there is another atom in the back and ranked 2 or 3, do you need to flip it over from S to R or what ?!
Nice, thanks. But you did not change the position of Cl and methyl group when you flipped the compound.
I didnt get sleep last night and I passed out in class so thank you for explaining this
You're very welcome!
very helpful, thank you
You are so welcome!
you saved me dude
Much love ....
Glad it helped! I would like to invite you to check out our monthly (no long term commitment) membership with over 1500 quizzes, flashcards the reaction guide and more. Here's access: bit.ly/2YctxPb
Sooo good thanks 👍
So I'm guessing this doesn't work if the hydrogen is in the plane of the page, only when it's in front/towards you?
Correct - in the case where H is in the plane of the page I would recommend swapping the H with whatever is the dash, and then determining R/S normally. Your "real" R/S will then be the *opposite* of that. This always works!
Yes. In practice, however, it's fairly rare to have hydrogen in the plane of the page, as the alkyl chain is usually in these positions.
Thank you.
hey thanks for the vid. are there exceptions in for wich the fast way does not work because i use it lot of time and sometimes it doesn't fit with the slow way. Thank you greetings from Switzerland. (My test is next week)
what if H is just on a normal line, do we still switch?
to this day, nobody seems to answer the question to Hydrogen being on the plane.
You may find our membership useful, here's a short video it's only a few minutes. Hope this helps - bit.ly/2YctxPb
@@MasterOrganicChem thanks but no thanks. An answer is all I need.
Nice video sir
Than you so so much
You're welcome!
The wedge on the hydrogen is pointed the other way, does that make any difference or was it just drawn funny?
Also what, we ignore the chlorine when moving things around but now all of a sudden when counting its included?
Put least priority group in the back,if it is not determine the configuration and reverse it
Bless you.
You need to be shown in which direction they go, or to be told that the stereocenter is R or S. If you are not given this information then it is typically assumed that the molecule is a "racemic mixture" with equal amounts of both configurations.
lovely, thanks a lot
So why on the bottom molecule you couldnt go clockwise at the beginning before you just flip it? because CH3 is just a line and so is CL. so why did you go counterclockwise going from 1-2-3-4? couldnt you go clockwise 1-2-3-4?
how to locate wedge and dash if we dont konw about them
Thanks
You're welcome! If you found this video helpful, Our MOC membership has a lot to offer. Check it out here: bit.ly/2YctxPb
Neat trick!!!
if you don't move the methyl group, but move all the other groups it doesn't work. In the video you moved all the groups except the chlorine group and it worked. Is it just trial and error?
Hi sir why aren't you uploading the videos pls try uploads atleast 1 video for 1 week because it will be helpful for many students of iit aspirants
Thank you
From India 🇮🇳
Will upload soon
@@MasterOrganicChem thanks for replying sir :)😊
On my homework, which is significantly harder than any example I can find online or which was given in class, all we are given is a name. (3R,6R)-3-bromo-6-methylcyclohex-1-ene. How in the world do you determine which is forward? IDK lost.
Amazing
that was very helpfull !!! :)
You are so welcome!
Skip to 3:45
Thankyou!!
You're welcome!
Subscribed
What if the H is in the plane of the page?! Plz help I have an exam in 2 days
I'm not sure I understand what you mean. Could you explain in more detail?
question again what if hydrogen is not above or below the plane of paper but on it ???
Are you saying that the "front" and "wedge" are the same thing?
Wedge refers the back, front is just front.
omg I finally understand this shit! Thank you!
You are so welcome!
What if #4 is in the plane?
What is r and s
i'm confused a little bit. I try to draw fisher projections for this example and everything goes wrong...😂
In fisher projection vertical line represents backward direction away from us which is simply equivalent to a dash bond... So if 4 th group is in vertical line ur answer will be according to clockwise or anticlockwise direction as normal case... But if 4th group (H) is in horizontal line jusy flip the direction and ur answer will be not the same... If it's coming r normally and 4th grp is in horizontal line the answer will be s not r...
Although I'm telling u this a little late like 2 years late😂👍
@@Mfsitsmatz hey should we flip it when 4th group is in horizontal line or only when it is forward/dark wedged?
It doesn't work if you fix the CH3 and rotate the rest
Thnx siR
ResPecT frOm INDia
But what if H is in the plane
You may find our membership useful, here's a short video it's only a few minutes. Hope this helps - bit.ly/2YctxPb
What if its in the side this is the so important here
hahaha. I went to a school called RNS. I wonder why we never made that joke when we were learning this XD because R and S sounds like R n S which is RNS LOOOOL
Why did I not just think of this?? Loll
you can skip the first 4 min it's just background
Clearly u should tell about ple I can't understand.. can u tell start from basic..ple 😁
It would be better, if you actually showed us...
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Wht the fuch this is really annoying version of you tube
Angrejiii ....kyoo hindii bolo naa
A North Indian asking an American to speak in Hindi lmaooo
thank you- very helpful video
You are so welcome!
Thank you for this!!
You are so welcome!
thank you!!!