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Introduction to chirality | Stereochemistry | Organic chemistry | Khan Academy

1767 ratings | 847674 views
Introduction to chirality (handedness), and how chirality is related to the groups bonded to a central carbon. Created by Sal Khan. Watch the next lesson: https://www.khanacademy.org/science/organic-chemistry/stereochemistry-topic/chirality-r-s-system/v/chiral-examples-1?utm_source=YT&utm_medium=Desc&utm_campaign=organicchemistry 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! About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. We tackle math, science, computer programming, history, art history, economics, and more. Our math missions guide learners from kindergarten to calculus using state-of-the-art, adaptive technology that identifies strengths and learning gaps. We've also partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content. For free. For everyone. Forever. #YouCanLearnAnything Subscribe to Khan Academy’s Organic Chemistry channel: https://www.youtube.com/channel/UCNKPjijOc0WEJ7DIV_Vay3g?sub_confirmation=1 Subscribe to Khan Academy: https://www.youtube.com/subscription_center?add_user=khanacademy
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Text Comments (156)
Mudassir Sayeed (24 days ago)
Your Orgo teaching skills are phenomenal Mr. Khan!
Surya Vikaas (2 months ago)
Sal, the mirror image to be produced is from the right hand( palm side) and not the left.
AK Gaming (3 months ago)
Death stranding.
Betsujin (4 months ago)
Kojima brought me here.
Tee Rex (4 months ago)
"I'm not going to write the whole thing" (Dead silence. No one arguing with you) "I'll just write the whole thing" hahaha Anyways this video/playlist is super helpful. Thanks.
Nguyễn Tiến (4 months ago)
A HIDEO KOJIMA GAME
IronVigilance Gaming (4 months ago)
I'm here to understand Death Stranding better lmao
雷KuZe (4 months ago)
IronVigilance Gaming 🙌
Mellissa Archer (5 months ago)
You are soooo Briliant....this made things super Clear, Big Thank You
VidaxTheDragonMage (5 months ago)
are chiral molecules always enantiomers?
Zarmin Khan (5 months ago)
Best 👏Thank you so much
Ron Zhang (7 months ago)
Thank evolution for inventing hands. Now I can take my hands to the exam and no one will punish me!
Hammad Hasan (7 months ago)
I always watch these videos at ×1.25 speed.
Aron Kibbelaar (7 months ago)
"I'm not gonna write the whole thing...." "Let me just write the whole thing."
David Townsend (8 months ago)
L-form and D-form, are how the molecule "bends light". R- and S- designation, are shorthand to distinguish between the two enantiomers, left or right handedness of molecule. Eg, when the smallest side group attached to a chiral carbon, is placed at rear of molecule, then the three other groups may rotate clockwise (R-), or anticlockwise (S-), going from heaviest side group, to second heaviest, then third. Oggston discovered that nature can tell the difference between 2 different, and two similar side groups, by the nature of attachment. The example Biochemists quote is cis-aconitate in TCA cycle. Might well apply to Glutamic acid, eg MSG. Hope it wasn't synthetically sourced, Chemists just don't get 100% Yields in such reactions (Racemisation)!!!
David Townsend (8 months ago)
Chiral centres are applicable in amino acids, though some are likely to be Oggston's 3-point attachment theorem. Hence, they are essential in enzymes (in nature L-form). So, primary, secondary, tertiary structures of enzymes would be altered by D-form, I believe.
David Townsend (8 months ago)
Imagine an enzyme as, a left hand glove on a right hand? Maybe, driving gloves?????
Aiza Saed (8 months ago)
"I am not gonna write the whole thing" "I m gonnna write the whole thing" 😂😂 SAL is the best💜💜
shakeela saeed (9 months ago)
Thank you so much....its so helpful
Juan Pablo (10 months ago)
Just one question, the hydrogen in the example( in between the other two groups) is in the centre it will still be in the centre which ever way it is rotated ???
Flying Spaghetti Monster (11 months ago)
I don't get the hands analogy, I can clearly overlap 2D hands.
xfactor139 (8 months ago)
letdomf I don’t think you are allowed to flip it. You can only rotate it clockwise or counter clockwise. You might get the fingers to over lap, but there is no way to get them100% lined up.
SIDDHARTH NANDIWADA (11 months ago)
You guys are doing a great job!!
焦雪源 (1 year ago)
actually i can still confused about why chirality exists
d pr (1 year ago)
thank you soooo much
CH3-CH2-CH=CH2 Is this a chiral compound?
An Nguyen (27 days ago)
i thought it would be chiral since it's asymmetric
school (1 year ago)
nope its not
Rashi Bhanot (1 year ago)
trumpo the president
Ilia Milan (1 year ago)
Thank you very much. Great
George M (1 year ago)
You need to stop repeating things over and over as you write... "4 different... 4... 4 different... different atoms". I love the videos, but this is quite irritating.
Bintou Waiga (1 year ago)
Studying for the MCAT! Ayy! Thank you! This really helped to refresh my memory!
Syed Moris (1 year ago)
Chiral is Greek for hand. Chiroptera is Bat with wings attached to its arms (ptera meaning wings like Archeoptra, Lepidopteron, Pterodactyl, Coleoptera). what I mean is cheir(chiros) means hand and its not a coincidence that hands are chiral(no plane of symmetry and all that) so we gave this name.
Keziah Niamh (1 year ago)
Isn't the CH3 supposed to be written in reverse on its mirror image?
Eason Rangarajan (1 year ago)
Keziah Niamh I think it's optional, as it represents a group
sathwik kumar (2 years ago)
what does super imposible mean?
damola muritala (2 years ago)
super imposable
TeaNcrumpets RS (2 years ago)
4:40 i think sal messed up the mirror image drawing of the molecule. the methyl group should have a dashed line and the hydrogen should have a wedged line
goclbert (2 years ago)
TeaNcrumpets RS That would be the same molecule. Sal drew the mirror image.
John C (2 years ago)
Superimposable***
mistree 000 (2 years ago)
after blackboard is full it looks so pretty with all those colors
señor shaman (2 years ago)
I was really worried: I've heard EVERYONE say how difficult oChem is. So when I heard of chirality, I was scared, but this concept comes extremely easy to me.
prateek gurjar (2 years ago)
if we rotate it in x axis 180° and then rotate it in z axis 180° we can superimpose anything...even.hands....why not molecules...they have rotational freedom in all three axes HELP
mistree 000 (2 years ago)
i was thinking the Same but i got it now
mistree 000 (2 years ago)
+themediawrangler i got the point ★ yas
themediawrangler (2 years ago)
try flipping your right hand so that it appears to be a left hand; now try grabbing something off a table with it...
shaminul loch (2 years ago)
hands are super imposible?
Umar Agraw (2 years ago)
No
Shot Dot (2 years ago)
Apparently this free drawing blackboard software is quite popular, as I have seen it used by Stanford online courses as well. Newsflash: it sucks. It is painful to watch instructor slowly handwriting words letter by letter. Look, there is a keyboard where you can type it. Or better yet, reveal the whole word or phrase at once. Like powerpoint slides do.
wish303 (2 years ago)
+Shot Dot I watch all the Khan lectures in 1.5 speed. It's much better at that speed.
Shot Dot (2 years ago)
+anna4tory Well, I just switched to competitor - AK Lectures. Whiteboard prepared in advance, good tempo, just as eloquent.
anna4tory (2 years ago)
I disagree. Love the blackboard approach.
Eric Terry (2 years ago)
Makes me think of a short story by Arthur C Clarke about a man who accidentally fell into a 4th dimension of space, resulting in all his molecules changing chirality. The result was that he could not attain nourishment from anything he ate and so started starving.
BLISS CINEMA (3 years ago)
you rock...
BLISS CINEMA (3 years ago)
you rock...
Maxwell (3 years ago)
Great video
Julien Prégent (3 years ago)
There's a spelling mistake in this video Sal!!! It's spelled superimposable not superimposible
Alexandra B (3 years ago)
if you take the mirror image of the chiral carbon, wouldn't the methyl group go toward the back and the hydrogen go toward us (the front)?
Oliver Isaac (2 years ago)
+andrew maldonado I was confused too but thanks, your explanation helped
andrew maldonado (2 years ago)
No but that's an easy mistake to make. Look closely at the planes in which each of the three groups below the carbon are in. If you looked at it from above (looking downward through the fluorine and carbon) you would see the molecules arranged methane, bromine, hydrogen (counterclockwise) on the left compound. If you looked down on the other it would be methane, hydrogen, bromine. If you rotated the left compound one "tick" counterclockwise, you would have the bromine in back and the hydrogen on the left.
Random Help (3 years ago)
Does he use a graphic tablet to write?
Eason Rangarajan (1 year ago)
Random Help Probably, its quite hard to write so accurately with a mouse
Ahmed Sameh (3 years ago)
*_* Super like (Y) (Y)
ThePieMan (3 years ago)
wow, I really can't thank you enough sooooo helpful! Thanks for taking time out of your day to make these videos, you help tons of students everywhere!
chemlover (3 years ago)
Why the carbon atom has to be surrounded by 4 diff. grps ? ie can't it be like ch3 | c / | \ f. br. ch3 Is this isn't chiral ?
chemlover (3 years ago)
+Gonçalo Policarpo kayy :) thanks a lot
Gonçalo Policarpo (3 years ago)
No, because later, to determine whether it's R or S, you have to choose priorities from 1 to 4, and you can't have 2 equal groups, because the priorities wouldn't work. 
Brenda Lu (3 years ago)
thank you!!!!
Redar Muhammad (3 years ago)
great illustration
fulufhelo nemutandani (4 years ago)
i am a south african student...just letting you know u helping even us who are so far away..thank you.
Wall9K (8 days ago)
Good to know this helps people far out anywhere.
Farhan Ahmed (11 months ago)
fulufhelo nemutandani I can totally relate with you. I'm from India and KhanAcademy is equivalent to a blessing here.
shao khan (2 years ago)
How dare you insult designated shitting areas
Maester Peemore (2 years ago)
+shao khan well you make nike trainers in india so i feel for you both
DOGE™ (3 years ago)
+shao khan don't let your dreams be dreams!!!!!!!!
HungryLioness (4 years ago)
i cannot express my love for this Organic chemistry videos. saving me in college :D
Jorn Van der Wal (4 years ago)
Chemistry, mathematics, or just hands in general  lmao
steve khan (4 years ago)
I'm a little confused, at 4:02 you mentioned carbon is bonded with CH 3 a methyl group ? isn't it an ethyl since it's two carbon and not one ? eth= 2 carbon, and meth=1 carbon ? or do i got it wrong ? 
Brian Joseph (4 years ago)
It's methyl.  When considering identifying a group you just identify what protrudes from the central Carbon...since only CH3 protrudes from the central Carbon than it is only a Methyl.  If you were to name the molecule though it would be Ethyl: 1-Bromo-1-Fluroehtyl (the rules for naming molecules IUPAC and naming groups can be a bit tricky and requires work to learn)
akshan1107 (4 years ago)
Sal's everyone's favourite uncle :)
metropolan (4 years ago)
I defy anyone to make sense of this. It seems like double-talk to me.
metropolan (4 years ago)
+Poliphodiles UniteI Oh, Alright!
metropolan (4 years ago)
+emcvagina123 Thank you!
Poliphodiles UniteI (4 years ago)
Get off youtube and read a book then.
krez (4 years ago)
visualising this with a set of model molecules is maybe a little easier to understand. The main point I see is the emphasis on a plausible product created in a mirror image, perhaps even structurally exactly the same, however, because of its orientation spatially (3D) it can not be placed (superimposed) back onto the original substance no matter how you try to spin it around etc. These differences lead into important theories relative to reactivity and R and S configurations
Keisha Pickrell (4 years ago)
I always look up your vid so I can understand organic chemistry. Thank you so much!
fung ben (4 years ago)
You r awesome!
Amy Thomson (4 years ago)
Thank you Khan Acad! Finally makes sense.
iman nasser (4 years ago)
i love you khan academy :') you make my life simpler. i like your handwriting 
leonardo vincent (4 years ago)
HEISENBERGGGG
Rajendra Chaturvedi (4 years ago)
Thanks....
Colette (5 years ago)
now i feel like I can teach others organic chemistry! A nice refresher course, wish I continued with organic chemistry in my degree...
famguy218 (5 years ago)
I have an orgo exam in 2 days; I was super pissed until I saw your videos.
bobagopaa (5 years ago)
BASED KHAN
Jeno Taengyai (5 years ago)
When I give a speech on my med graduation day, I will say 'I would like to thanks those who has always been there for me, and those are, Mr Google, KhanAcademy and Mr YouTube'.
Em A (5 years ago)
SOOO HELPFUL. Thank you so much for taking the time to make all these videos!
ABDALLA ABDRABOU (5 years ago)
how do i rotate the molecules ....i mean if o have rotated 180 degree it woulf fit and become superposable...plz explain it drives me crazy this rotation part
Charles Mehtanza (5 years ago)
My name is Chiral.
Nicole Hilton (5 years ago)
Thank you for this! definitely saved me from flunking the exam
kru1552 (5 years ago)
It is also called a stereogenic carbon.
dddownsu (5 years ago)
Anyone else here for tomorrows chemistry exam? (EDEXCEL)
jenniferelisa (5 years ago)
You are litterally saving me with these videos. I don't get anything in Chemistry but this is wow. So thank you!!
knucklescapricorn31 (5 years ago)
Thank you so much, this helped me out heaps!!!
amaan sawrar (5 years ago)
the dislikes are from bitter teachers.....lol u rock and make chemistry a cakewalk for me...thanks...
wigglesza (5 years ago)
I feel like that's how much of chemistry works
john hug (5 years ago)
your explanation is fantastic thank you alot!
Pouria Ghavami (5 years ago)
Dear Salman Khan, We shall throw out all the other crapy teachers let them flip burgers and give their salaries to you. God Belss You
aya delfi (5 years ago)
thank Mr khan!!!! your a star!
pinkhue (5 years ago)
I LOVE YOU this makes sense
meduzzaZA (6 years ago)
lol, I think the only people who can possibly dislike the video would be my prof and TA.
VinnyMartello (6 years ago)
I sit in class for 1 hour and 20 minutes hearing the droning of a refrigerator and learn nothing. I sit here for 6 minutes and it starts to make sense.
Quintinohthree (6 years ago)
Depends on what symmetry they have. Even chiral molecules can have symmetry of some sorts.
Dunkusbunkus (6 years ago)
Wait so are only asymmetrical molecules chiral, or can symmetrical molecules be chiral?
Persiancat (6 years ago)
my brain hurts when i'm trying to visualize :(
Electrohin (6 years ago)
i did not get it!!..whaaa!!
Skand Tripathi (6 years ago)
shouldn't be the me be at the back an h at front in the mirror image
mashnbangers22 (6 years ago)
cutest friggen hand drawing evah
ChaoticSerenity (6 years ago)
Thank you sir for helping to simplify the only chemistry I've taken where I can feel the air stir above me as the entire lesson flew over my head.
DaKingCobra11 (6 years ago)
@DaKingCobra11 The hand example is a 2 dimensional figure so I can rotate it to be superimposable.. But if it was SP3 molecule you couldn't superimpose them.... am I seeing this right?
DaKingCobra11 (6 years ago)
But if u rotate the left hand 360 degrees u CAN superimpose them to be identical... they just face the the opposite direction... am I seeing this wrong...???
def4983 (6 years ago)
OH MY GOD THIS PROFESSOR FUCKED MY GIRLFRIEND I AM SO PISSED OFF UGH!!!
s0m0c (6 years ago)
Gracias.
Belieber BU (6 years ago)
OMB thaxx a looooot!! You don´t how much u´ve helped me ;)
getsmarter82 (6 years ago)
@geeca85 I see what you did there...
VitaminMePlease (6 years ago)
@Casowsky i didn't catch that but that's why I love him. So patient lol.
Alex Bertsch (6 years ago)
Some hands on learning, going on here.
Jules (6 years ago)
@TheLonghairraven Think about your own hands and not the drawing... if you were to put your left hand on your right hand, your nails on one hand would be towards you, and your nails on your other hand would be away from you.
Andy Tuck (6 years ago)
So the two carbons in the top right are chiral? But they are bonded to the same four groups, just in a different 3D shape...
Areeb Asifee (7 years ago)
Sal I hope you know that you are an inspiration to millions of students around the world watching your videos everyday. I really wish you the best and may you succeed in everything you wish to accomplish
tubeyou1901 (7 years ago)
i used to watch random useless failblog videos when i was procrastinating. but now i watch Sal's videos when im bored and dont feel like studying!!

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