5.6 Amine Inversion and Chiral Molecules without Chiral Centers

5.6 Amine Inversion and Chiral Molecules without Chiral Centers | Organic Chemistry

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Chad covers a couple of unique topics involving chirality. The first is amine inversion. Many amines undergo inversion of configuration at room temperature which leads to them technically be classified as achiral. The second is chiral molecules without chiral centers. Chad shows how certain allenes and ortho-substituted biphenyls have the unique property of possibly being chiral without having any chiral centers.
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00:00 Lesson Introduction
00:38 Amine Inversion
03:07 Chiral Molecules without Chiral Centers: Allenes
07:49 Chiral Molecules without Chiral Centers: Biphenyl
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Пікірлер: 17

@shivamehra4420 2 сағат бұрын

Sir that means the compounds which are symmetrical about any axis But not optically Inactive are Chiral without chiral centre.

@MiaClare-sn8cc 9 ай бұрын

Going back and reviewing my ochem. Where were you those years I was taking it!😂 great videos! Thank you!

@ChadsPrep 9 ай бұрын

Thanks - glad the channel is helping you now!

@user-pj5bk7ds8u 4 ай бұрын

Thank you for the explanation with 3D drawing of allene.

@ChadsPrep 3 ай бұрын

You're welcome

@sciencenerd7639 2 жыл бұрын

fascinating

@ChadsPrep 2 жыл бұрын

Good!

@watchgoon9 Жыл бұрын

Did u mean odd number of allenes?

@olaholvik6510 Жыл бұрын

realy thanks i stopp to see all other Chanels. can you please say how many chiral is in the second drawing, and which one ? the drawing is on minutt 08:00.

@ChadsPrep Жыл бұрын

Are you asking how many chiral centers there are? In those cases we have chiral molecules without chiral centers (remember chiral centers have four different groups attached) since all atoms have double bonds.

@user-vo5qb8cn5e 5 ай бұрын

Hey, thanks for the video. I have a question about chirality and symmetry breaking. In the video you say that amines, because they can invert, are not chiral molecules. However, in other contexts I have read about other molecules that are chiral by definition but can still invert. My question is whether chiral molecules definitely cannot invert and if so, why? Does it have anything to do with the presence of a chirality center?

@ChadsPrep 5 ай бұрын

The difference between amine inversion (pyramidal inversion) and inversion of other chiral compounds is the energy barrier associated with it. Amines have a low energy barrier for inversion and so do invert rapidly at room temperature even which prevents optical activity due to the rapid racemization. Other chiral compounds have higher energy barriers for inversion dependent on multiple factors and so they can be inverted by reactions or energy input. However, as they are naturally found they are optically active and so considered to be chiral. Hope that helps!

@user-vo5qb8cn5e 5 ай бұрын

Thank you very much! Could then theoretically every chiral molecule be inverted by energy input? Or are there also cases where it is only possible through reactions? Or cases where it is completely impossible?@@ChadsPrep

@ChadsPrep 5 ай бұрын

Pyramidal inversion is only possible for tetrahedral species having 1 lone pair of electrons on the central atom. Whereas for nitrogen the energy barrier is low, it is higher for phosphorus and separate enantiomers of chiral phosphines can be isolated. But such inversion does not generally occur for chiral centers that do not have a lone pair of electrons, but there are notable exceptions such as the alpha carbon of a carbonyl containing compound. Depending upon acidity/basicity, such a species may be in equilibrium with its enol or enolate form in which the alpha carbon is sp2 hybridized and trigonal planar. When it converts back to its carbonyl form, it becomes sp3 hybridized and could potentially form a different stereoisomer if it is a chiral center. So this is not an energy barrier per se, but a reaction. Hope this helps!

@user-vo5qb8cn5e 5 ай бұрын

Thank you@@ChadsPrep

@ChadsPrep 5 ай бұрын

@@user-vo5qb8cn5e Very welcome