Chiral centres in a phthalimide-like structure..

[SuperSaiyan3]

There is a difference between chiral centres and chiral carbons.

Centres also constitute any chiral nitrogens, sulfurs.. etc.

What I wanted to ask was:

1. is a tertiary nitrogen in a CYCLIC structure chiral?

- I know that a tertiary nitrogen on its own is not chiral because the lone electron pair can invert freely, thus eliminating chirality. But if it's in a cyclic structure, would it not STUCK in that position, unable to invert? Therefore, would it not be considered a chiral centre? I ask this because a Kaplan question I did not too long ago (but can't find it) indicated that it was not a chiral centre.

2. consider the structure of a phthalimide. http://en.wikipedia.org/wiki/File:Phthalimide.png

- okay, so this isn't the structure that I want to discuss. But imagine that the aromatic ring is hydrogenated thus it is a cyclohexane, and not a benzene ring.
- with this new structure in mind, would you say that the carbon ALPHA (left of) to the carbonyl group's carbon is chiral? I don't see what it would not be... again, I thought this would be a chiral centre but it was not.. as indicated by kaplan. It would have a -H group, and 3 different carbon links, would it not??

Thanks guys.

SS3

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[loveoforganic]

1. Why are you thinking a cyclic amine could not invert?

2. Looks chiral to me.

 

[SuperSaiyan3]

wouldn't a cyclic ring essentially hold the structure in place?

From my knowledge, I know that methyl bridges are made in cyclohexanes to prevent ring flippage... I just assumed that a ring structure would prevent the nitrogen from flippping. Is this not valid?

I'm gonna try to find the structure that they showed me in kaplan. How do i post images on here?

 

[SuperSaiyan3]

hope you guys can see it

 

[SuperSaiyan3]

ahh... Okay so in regards to my inquiry #2, looks like I was genuinely wrong. The carbon I was looking at was a benzene carbon, so it's not chiral. But if it wasn't, it would be chiral eh?

In regards to my inquiry 2, take a look at the nitrogen atom (NH) in between the 2 carbonyl groups. Kaplan says that it will have the power to invert, but I thought otherwise because it was in a ring. Am I wrong?

 

[loveoforganic]

Well, I'm guessing here, but I'd say Kaplan is wrong in their explanation but right in their answer. I'd say that nitrogen is significantly less likely to invert at room temperature than an amine due to the fact that it's part of an imide functional group - the lone pair resonates between bonding to the two carbonyl carbons making the nitrogen essentially sp2.

 

[SuperSaiyan3]

Well, I'm guessing here, but I'd say Kaplan is wrong in their explanation but right in their answer. I'd say that nitrogen is significantly less likely to invert at room temperature than an amine due to the fact that it's part of an imide functional group - the lone pair resonates between bonding to the two carbonyl carbons making the nitrogen essentially sp2.

AH! you are right!

didn't even think about resonance.. darn.

Thanks,

I'll have to keep that in mind for peptide bonds for sure..