[idis]

hey guys, can anyone tell me if this multiplete is a doublet of triplet (dt) or triplet of doublets (td)? i'm confused because in the book says it's dt (7,40, dt, 1H, J1 = 0,97 Hz, J2 = 7,74 Hz, Harom.) but to me it looks like a td, and when i calculate the coupling constants (for td) i get 0,97 and 7,74 Hz.

[Arkcon]

It would probably be best to give us some context -- show us more of the scan, and give us some idea of what the sample is.

[hypervalent_iodine]

It would be useful to know some more structural information on the compound. You could also make a case that it is a ddd, with overlapping signals in the middle (I see a lot of these in the aromatic systems I work with), but it's hard to know what it is without knowing where it comes from.

In any case, I am not sure I would confidently report it as being anything in particular. You cannot clearly see the splitting in the middle peak, and you can only report what you see. If it were me, I would have reported it as a multiplet and just given a range. 

[Irlanur]

ehm... a doublet of a triplett is the same as a triplett of a doublet, given that the coupling constants for each of the two remains the same.

[hypervalent_iodine]

ehm... a doublet of a triplett is the same as a triplett of a doublet, given that the coupling constants for each of the two remains the same.

They are certainly very closely related, but not the same. If you consider a system -CH(a)-CH(b)-CH₂(c)-, The peak for (b) will either be a td or dt, depending on whether J(b)-J(c) coupling is bigger or smaller than J(b)-J(a). You could not call it a td / dt interchangeably.

If you absolutely had to choose between the two for the peak in the OP, and having only as much information as they have given, I would be inclined to go with td as they did. However, peaks can overlap and make it hard to really tell what's going on. Knowing more about the structure would give an indication as to which J coupling would be greatest, and therefore whether or not it is a td or dt.

[Irlanur]

you have a triplet with a certain coupling and a doublet with a certain coupling. There is no way in telling which of the ones "splits first". There might be conventions where you put the bigger coupling first, but it simply doesn't matter.

You could not call it a td / dt interchangeably

Yes, you can, if you give the coupling constant for d and the constant for t.

I could start with math but let's not do that for a moment.

[idis]

Hi, this is the 1H NMR spectra of 2-cyanomethyl-N-methylbenzimidazole, there are 4 aromatic protons on the benzimidazole ring: 1H(DMSO, 300MHz): 7,63 (dd, J₁=1,47 Hz, J₂=7,41 Hz), 7,55 (dd, J1=1,47 Hz, J2=7,50 Hz), 7,27 (dt, J1=1,38 Hz, J2=7,50 Hz), 7,22 (dt, J1=1,39 Hz, J2=7,45 Hz) Why are the two signals on the right doublets of triplets? aren't they tiplet of doublets? coupling constants values are matching to td.


**mod wildfyr** split into a new topic, this had nothing to do with the original post.

[clarkstill]

You're right, in the sense that the triplet is the higher J-value coupling so according to convention should come first, but the coupling constants are also written in the reverse order so at least it is clear (i.e. the peak at 7.27 should be td, J1 = 7.5, J2 = 1.4).

[Arkcon]

Hi there, idis:, I've merged your two posts into one thread, and I apologize to you and everyone else for the doing that makes of the thread.

Its useful, sometimes, to have everything that a person knows, and more important, everything our regulars have told them recently, in one thread, so we know what to say next.

Some housekeeping:  Please don't post a new question in someone else's thread.  Create your own New Post:, with a good title, and give us a good description of what you know, and what you need help with.