Cahn-Ingold-Prelog system for naming enantiomers | Organic chemistry | Khan Academy
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- Опубликовано: 8 фев 2025
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Cahn-Ingold-Prelog System for Naming Enantiomers. Created by Sal Khan.
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You know what i like about you? you don't assume your students know everything. Where you noted the reason its 1-Bromo-1-Floroethane and not 1-Floro-1-Bromoethane, my Ochem professor would have just named the molecule and if you didnt know why then it just leaves the students confused. Everything is explained as you go when you teach. Its a great way to teach, I really appreciate it.
My professor would have done the same. Like, just explain why.
"But its a different Cahn, its not me.." lol
@prolarka We're rotating 1/3 of the way around a circle so it would be 360/3 or 120 degrees.
"its a different khan, its not me" i was waiting for it, i was fully expecting it, but idky that still cracked me up way more than it should have lmaooo i was sittin here laughing to myself for like a minute straight🤣
So is Sal a robot or how is he so good at everything?!
represent atk. that guy too
I think your tagline should be "Khan Academy: Better (and cheaper) than any MCAT prep course out there!"
you have no idea how much you've helped me, thanks a million khan :)
@unknwn2312 Remember to think of these molecules as "tripods." It really helps when it comes to understanding the rotations. In this particular case think of the Bromine as the spot where the camera goes and the rest of the groups as the legs. No matter how many degrees you rotate the molecule the Bromine will always be on top. If you have a tripod get it out and give it a try.
Sweet video. Also, on a semi-related note, I believe the negative meaning of Sinister comes from Hebrew. In ancient Hebrew culture the left hand was a symbol of personal power and authority, which many leaders didn't like for obvious reasons. This meaning eventually traveled around the ancient world and went from a symbol of power to a symbol used to mock or otherwise threaten those in power. Christianity came along and associated it with disbelievers in God and His authority.
KA, I wanna thank you for saving my life. Honestly, grades are my life and I actually because seriously depressed when I didn't understand my poorly written text book :'( KA, my heroes
You said it here and there in this and the other videos... in subordinate clauses...WHY we are doing naming things "chiral" and more.... Could you gather the reasons and motivations for all the chiral "things"?
Excellent video. Keep on going.
THANK GOD for sal
this video is so well explained; good advice on how to reorient the molecule as well, which is the most difficult part.
As always, thank you khan.
WOW!!! Thanks a lot Khan, you are of a good help
watching this 20 minutes before exam lets go!
Really good video, you obviously have talent for explaining, you helped me a lot for my future exam, thanks for that.
OMB thxx a lot. U explained it soo well
Omg, I should've watched this before before my midterm ): Thank you so much!!!
Rectus means "straight" not "right", dexter would be right
thanks alot ,you explain the lessons very well , thanks from my heart❤
Thanks, No Bromo.
keine031 lmao
You've been a great help
thank you the visualization clicked! helpful!
Hey Khan you should definately petition to have this system renamed to Khan-Ingold-Prelog System
Great! 👍
thank you, this really helped
Thanks really very beneficial videos
There is a shortcut! in this case the lowest priority was in front of the molecule-- skip any rotation steps, and go from 1st to 2nd to 3rd priority. What you get (S) or (R) is simply the opposite of whatever you get! ONLY if 4th priority starts in front though.
Very enjoyable thank you
they should have called it khan-alone system, because he is the only one who actually explained his stuff =P
Thank you so much!!!
In the past, to be left-handed was considered touched by the Devil. As Wikipedia notes:
Historically, the left side, and subsequently left-handedness, was considered negative in many cultures. The Latin word sinistra originally meant "left" but took on meanings of "evil" or "unlucky" by the Classical Latin era, and this double meaning survives in European derivatives of Latin, and in the English word "sinister".
Ooh, interesting. Thanks!
You are correct.
Thanks a lot !
thank you very much ;-) even for a german it is good to understand!
Hi there, and may I congratulate you for your excellent teaching. Question, from min. 5:00 -> You say that we have to rotate the arrangement so that the lowest group "sits" behind the molecule, and you rotate it using the Br - Carbon bond as an axis... now, would it be possible to use the Methil - Carbon bond as an axis (so that CH3 stays fixed and Br, and H rotate) ? And if possible, would this implicate different results ? Thanks in advance for both your answer and videos!
thank u khan
C-H-A-N / K-H-A-N -----> Enantiomer! LOL, why did i find this hilarious.
+lone wanderer its a diastereomer sherlock
Actually, neither, it's not even a stereoisomer.
Thanks
thanks a lot I was really lost
Gracias.
So their tetrahedral orientation, determines how they will react. The r would react differently to the s orientation. Because of their ''atomic positions'' they would have different reaction. Maybe because of how these same molecules will react to each other based on how they were situated.
In my chemistry book - the latin word for left and right is Laevus (left,) and Dexter (right). They put D and L in front of the names... It seems both names stand for the same thing. Is these used differently depending on country?
Love u sal
my love for you is describable
Thought of giving up an exam ,my friend let me know abt your channel,I think i can ,lets see
What happens if you have 2 different groups that have the same atom bonded to carbon?
Hey Sal! Great video as always :) I am a little confused about why this molecule is 1-bromo-1-fluoroethane though. Why cant we just call it bromofluoroethane?
We can.
for the molecule couldnt you just call it 1,1 bromofluroethane? or since its only 2 carbons cant u just also say bromofluoroethane?
How do you have stereoisomers for an alkAne, is the sigma bond not able to rotate, thus eliminating the possibility for an isomer for a 2 carbon molecule?
Will u please tell me configuration in reboxetine
I use to remember (S)-Anticlockwise, so SANTI
Sir cahn - ingold - prelog priority rule
Prelogs rule these two are same are not please tell me sir
Prelog is from Croatia. Actually, my org. prof. knew him.
If you have to do a swap of groups doesn't that change the original (R) to a (S)?
+Deedra Blevins I thought the same thing, but he didn't swap the groups. He rotated the molecule. So it wouldn't change the R/S configuration.
No... He just changed the conformation
wait question, when you first named the molecule, what about the hydrogen??
Can we also say 1,1 - Bromo-Flouro Ethane?
Yes, but it would be written as 1,1-bromoflouroethane. You can also leave off the numbers and it would be assumed that it is bonded to the first carbon, making it bromoflouroethane.
How can you say CH3 is #3 just because of the C(12) is No.3 in serial?
Cz It's just not the C rather CH3.
Why didn't you count the 3 H?
If H shouldn't be counted then why did you count H at #4?
And then, how can you call the middle Carbon a chiral Carbon if it's connected to another just Carbon(as u didn't count those Hydrogens)?
..
Or did you count as CH3(15) as a whole & then called it called it #3 as it's also #3?
Okay, when we're rotating the molecule and are finished rotating the molecule at 6:44... shouldn't the methyl group be on top and the Bromine be coming out of the page?! OMG.
I AM SO CONFUSED.
@khanacademy ture, 1st i thought fluorine is closer than the hidrogen, my fault
wait....so when rotating the molecule we can just rotate the "tripod" and ignore the top constituent?
when you rank them by atomic mass why do you only consider carbon in CH3? Why dont you consider the entire group CH3?
The carbon in the methyl group is the only atom bonded to the chiral carbon. You only look the one atom that is the first point of difference from the chiral carbon.
6:30 not 120, its about 60
@khanacademy
For God's sake, thank you !!!
I'm from Croatia and I was sad when I herd you say Prelog wrong. Please, check pronunciation before saying such names.
Thank you very much for everything! :D
👍👍👍👍👍👍
#21
i love you
what if all the atoms are hydrogen? eg methane
Daniel Persaud it ain't chiral...
Cahn-Ingold-Prelog System?
Those silly chemists misspelled 'Khan"
Actually, I think I get it now... haha.
such a hot video.
marry meeeeeee
He takes too long to get o the point, it's so annoying.
He's drawing it literally, and a lot of people tend to find his style useful apparently. Just increase the speed, that's what I do, and stop complaining. Instead thank him for being God-sent. Seriously.
Rah L
Use this saying to remember: R rolls forwards, S spins backwards.