Chiral Tertiary Amines?

[justadream]

So are tertiary amines (with 3 unique substituents) technically chiral? I know they undergo nitrogen inversion, making the two enantiomers (or diasteromers, if the amine is attached to some other chiral centers) not resolvable?



My textbook (Wade Organic Chemistry) calls the two possible structures from nitrogen inversion of isolated (by that I mean, not connected to anything else) tertiary amines “enantiomers”.

So they should be considered chiral but racemic?

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[NextStepTutor_1]

So are tertiary amines (with 3 unique substituents) technically chiral? I know they undergo nitrogen inversion, making the two enantiomers (or diasteromers, if the amine is attached to some other chiral centers) not resolvable?



My textbook (Wade Organic Chemistry) calls the two possible structures from nitrogen inversion of isolated (by that I mean, not connected to anything else) tertiary amines “enantiomers”.

So they should be considered chiral but racemic?

Let's look at what a tertiary amine looks like:

http://en.wikipedia.org/wiki/Amine

The nitrogen in a tertiary amine is bound to 3 carbon substituents (represented in the table as R groups).
Chirality exists when two structures are non-superimposable mirror images of each other - the quintessential example being your left and right hand. However, for the purposes of the MCAT, you can also take chirality to mean that there exists a carbon bound to 4 different substituents. Under this context-specific definition, the nitrogen of a tertiary amine is not chiral. HOWEVER, that is not the same as saying the compound itself is not chiral - if it has at least one chiral carbon then it is a chiral compound (i.e. if one of those R groups in the table represented a chiral carbon then the amine molecule would be chiral).

I hope this clears up your confusion some.



http://forums.studentdoctor.net/forums/next-step-mcat-tutor-office-hours.970/

 

[justadream]

@NextStepTutor_1

So then this wouldn't be chiral because here, the 2 R-groups are achiral?

 

[NextStepTutor_1]

Your chemistry book is providing more detail than you need to know.
With regards to the scope of chirality that is tested on the MCAT, the ethylmethylamine you provided in the diagram is NOT a chiral compound because there is no chiral carbon. Your reasoning is spot on.