[Babcock_Hall]

https://organicchemistrydata.org/hansreich/resources/nmr/?index=nmr_index%2F13C_shift#cdata84

Good Morning,

We made (EtO)₂P(O)CH₂C(O)N(-CH₂CH₂OCH₂CH₂-), where the amide is the morpholine group.  As expected, four of the carbon atoms showed coupling to phosphorus.  There are two signals, 47.3 ppm and 42.4 ppm, that I believe to be -NCH₂- groups.  Given that there is restricted rotation around the amide (-NC(O)-) bond, seeing two peaks is understandable (see link for a couple of examples).  However, the peak that I assigned to -OCH₂- at 66.7 ppm is the only signal in this region other than the CH₃CH₂[/sub]O- peak, which is one of the doublets.  I am a little puzzled why restricted rotation would affect one carbon atom and not the other.

Later I may post a little bit about the H-1 spectrum as well.

[rolnor]

To see the effect off restricted rotation the atom needs to get two different environments magneticaly, mayby one off the atoms does not have this?

[Babcock_Hall]

A colleague of mine suggested something similar, which is that the difference in the two environments of the CH₂O groups may be small enough to put these two nuclei into the fast-exchange regime.  I need to refresh my memory on chemical exchange to make sure that I understood correctly.

[rolnor]

Its at least possible, can you maybe cool the probe? Or look at proton-nuclei?

[Babcock_Hall]

I just looked at the H-1 NMR.  The 8 hydrogen atoms of the morpholine group form a multiplet centered near 3.68 ppm.  It looks like a triplet in which each of the three signals is further split into two or three signals.

When I went to Hans Reich's site, I found a few examples of amides in which the two carbon atoms directly attached to the nitrogen atom had C-13 chemical shift differences around 2-3 ppm.  I have not searched extensively for morpholine-containing compounds specifically.

[rolnor]

Great! You have plain DMF with large differences in shift...

[Babcock_Hall]

I am sorry, but I do not follow you.  Do you mean that DMF is a model compound?  One of the models at Hans Reich's site is N,N-dibenzyl-2(triphenylsilyl)acetamide.  The benzylic -CH₂- groups are found at 48.2 and 50.7 ppm.

[rolnor]

Yes, I mean that the compound you have can be more prone to restricted rotation than DMF because its a larger molecule. Maybe its not a very important observation. You have been working on these compounds for some time now, how are you doing, do you see any more bio-activity? Do you have any progress?

[Babcock_Hall]

I have seen some astonishing results in whole cell assays.  I need to raise my game synthetically.

[rolnor]

Great! Please let me now if I can help you. That explaines why you continue the work then.

[wildfyr]

At this point you should consider giving Rolnor the lowest priority authorship if you write a paper

[rolnor]

Aaaahhh, that was nice wilfyr, I give you a molsnack!