Cahn-Ingold-Prelog system for naming enantiomers | Organic chemistry | Khan Academy

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Cahn-Ingold-Prelog System for Naming Enantiomers. Created by Sal Khan.
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Organic Chemistry on Khan Academy: Carbon can form covalent bonds with itself and other elements to create a mind-boggling array of structures. In organic chemistry, we will learn about the reactions chemists use to synthesize crazy carbon based structures, as well as the analytical methods to characterize them. We will also think about how those reactions are occurring on a molecular level with reaction mechanisms. Simply put, organic chemistry is like building with molecular Legos. Let's make some beautiful organic molecules!
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[@panmaru101]

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.

[@oyeludejomiloju704]

My professor would have done the same. Like, just explain why.

[@khanacademy]

@prolarka We're rotating 1/3 of the way around a circle so it would be 360/3 or 120 degrees.

[@yeedoh]

"But its a different Cahn, its not me.." lol

[@F0A0Y0N0U0S]

@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.

[@NiallBucks]

So is Sal a robot or how is he so good at everything?!

[@saddamali666]

represent atk. that guy too

[@sameerakkad2120]

you have no idea how much you've helped me, thanks a million khan :)

[@darraghh6384]

this video is so well explained; good advice on how to reorient the molecule as well, which is the most difficult part.

[@chrismartin1985]

I think your tagline should be "Khan Academy: Better (and cheaper) than any MCAT prep course out there!"

[@Melthornal]

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.

[@sirleeeros7583]

WOW!!! Thanks a lot Khan, you are of a good help

[@Zay658]

THANK GOD for sal

[@norwayte]

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.

[@keysaysassah]

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

[@aviramwolfstein4443]

As always, thank you khan.

[@patrickcorcoran8183]

Rectus means "straight" not "right", dexter would be right

[@Mickster114]

"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🤣

[@MileyAshleyfan78]

OMB thxx a lot. U explained it soo well

[@TomNEEG]

You've been a great help

[@keine031]

Thanks, No Bromo.

[@DMMBX3]

keine031 lmao

[@jrbertot2010]

thank you the visualization clicked! helpful!

[@canaliscarpi]

Really good video, you obviously have talent for explaining, you helped me a lot for my future exam, thanks for that.

[@tomaa_sh]

Thanks really very beneficial videos

[@muskankapoor5085]

thank you, this really helped

[@philster00700]

You are correct.

[@curtpiazza1688]

Great! 👍

[@zahraaanas174]

thanks alot ,you explain the lessons very well , thanks from my heart❤

[@smuggecko]

Very enjoyable thank you

[@la-margriffiths2481]

watching this 20 minutes before exam lets go!

[@gunner199312]

Thank you so much!!!

[@minivaans]

Omg, I should've watched this before before my midterm ): Thank you so much!!!

[@s0m0c]

Gracias.

[@redhotpilgrim]

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.

[@tuberweba2052]

Thanks a lot !

[@arvindkumarm1927]

thank u khan

[@TheFischfreak]

thank you very much ;-) even for a german it is good to understand!

[@Airkilla09]

Hey Khan you should definately petition to have this system renamed to Khan-Ingold-Prelog System

[@RightCenterBack]

Thanks

[@sinethembaneliswa8131]

thanks a lot I was really lost

[@robertmz22]

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!

[@jigabi2085]

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.

[@elvismesa7306]

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".

[@MonkeyDLuffy-xr4fl]

Ooh, interesting. Thanks!

[@CitriReg]

Love u sal

[@TheMedhero]

they should have called it khan-alone system, because he is the only one who actually explained his stuff =P

[@FlashySenap]

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?

[@Mickster114]

for the molecule couldnt you just call it 1,1 bromofluroethane? or since its only 2 carbons cant u just also say bromofluoroethane?

[@ThePeterDislikeShow]

What happens if you have 2 different groups that have the same atom bonded to carbon?

[@CHeh-wv1sx]

C-H-A-N / K-H-A-N -----> Enantiomer! LOL, why did i find this hilarious.

[@SandFoxling]

+lone wanderer its a diastereomer sherlock

[@MonkeyDLuffy-xr4fl]

Actually, neither, it's not even a stereoisomer.

[@davecampbell892]

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?

[@deatheth5039]

We can.

[@ajaysalunke6288]

Will u please tell me configuration in reboxetine

[@Tnpscremembertricks]

Sir cahn - ingold - prelog priority rule Prelogs rule these two are same are not please tell me sir

[@skittless3949]

wait question, when you first named the molecule, what about the hydrogen??

[@olisho7251]

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?

[@gardening1049]

Thought of giving up an exam ,my friend let me know abt your channel,I think i can ,lets see

[@unknwn2312]

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.

[@dugudwn]

Can we also say 1,1 - Bromo-Flouro Ethane?

[@rcwcello5607]

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.

[@spectrum792]

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?

[@prolarka]

@khanacademy ture, 1st i thought fluorine is closer than the hidrogen, my fault

[@norcoboy]

wait....so when rotating the molecule we can just rotate the "tripod" and ignore the top constituent?

[@superfruit2]

my love for you is describable

[@deedrablevins2362]

If you have to do a swap of groups doesn't that change the original (R) to a (S)?

[@soneinspirit7]

+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.

[@MonkeyDLuffy-xr4fl]

No... He just changed the conformation

[@ciao_abhi]

when you rank them by atomic mass why do you only consider carbon in CH3? Why dont you consider the entire group CH3?

[@rcwcello5607]

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.

[@TheMiiirna]

Prelog is from Croatia. Actually, my org. prof. knew him.

[@otivaeey]

I use to remember (S)-Anticlockwise, so SANTI

[@prolarka]

6:30 not 120, its about 60

[@nihayaturrohmah4230]

#21

[@SuperAnju24]

@khanacademy

[@pujeetjha8265]

i love you

[@maitrithakur7130]

👍👍👍👍👍👍

[@corentinevezard4990]

For God's sake, thank you !!!

[@skembow]

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

[@danielpersaud7161]

what if all the atoms are hydrogen? eg methane

[@aggricor]

Daniel Persaud it ain't chiral...

[@Marinecorps1812]

Cahn-Ingold-Prelog System? Those silly chemists misspelled 'Khan"

[@unknwn2312]

Actually, I think I get it now... haha.

[@TeKNiQ50]

such a hot video.

[@bonitachica786]

marry meeeeeee

[@BlueUKLouis]

He takes too long to get o the point, it's so annoying.

[@MonkeyDLuffy-xr4fl]

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.

[@musicaperuana2380]

Rah L

[@skinlessboy]

Use this saying to remember: R rolls forwards, S spins backwards.

[@flirtatiousdisses]

sinister lol