N and chirality

[Xtian]

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N atoms bonded to three different substituents are chiral because of the geometry of the orbitals. Why is this true?

I'm guessing that this is because of N's sp3 hybridized state. So does the lone pair count as a different substituent, and help rotate light?

-Xtian

 

[Xtian]

anybody know about this? Thanks in advance,

Xtian

 

[PinkDDS]

The three different groups are non-superimposable mirror images due to the pyramidal structure of the tertiary amine.

The lone pairs do count as a substituent.

 

[Xtian]

how can N with three different constituents be chiral?

 

[PinkDDS]

The lone pairs are counted as substituents so the nitrogen has 4 different groups. These groups are non-superimposable mirror images. This is the definition of chirality; as a result a tertiary amine is chiral, but it's not optically active because of inversion.
I hope this helps🙂

 

[Xtian]

that does help, thanks!

FYI to anyone else...Kaplan says this is due to the geometry of the orbitals. Certain amines can be optically active if the inversion is hindered by the structure .