July 04, 2022, 07:24:08 AM
Forum Rules: Read This Before Posting


Topic: nmr interpretation  (Read 10779 times)

0 Members and 1 Guest are viewing this topic.

Offline AMARACHUKWU

  • Regular Member
  • ***
  • Posts: 10
  • Mole Snacks: +0/-0
nmr interpretation
« on: May 09, 2018, 06:44:35 AM »
i am a postgraduate student of organic chemistry with little knowledge of characterisation and interpretations of nmr spectra . i need help.

Offline sjb

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 3641
  • Mole Snacks: +220/-42
  • Gender: Male
Re: nmr interpretation
« Reply #1 on: May 09, 2018, 06:58:57 AM »
How did you study this at undergraduate level - e.g. what were your course books, what did you cover (just proton and carbon, or other nuclei as well?)

Offline AMARACHUKWU

  • Regular Member
  • ***
  • Posts: 10
  • Mole Snacks: +0/-0
Re: nmr interpretation
« Reply #2 on: May 09, 2018, 07:11:34 AM »
just proton and carbon.

Offline AMARACHUKWU

  • Regular Member
  • ***
  • Posts: 10
  • Mole Snacks: +0/-0
Re: nmr interpretation
« Reply #3 on: May 09, 2018, 04:55:47 PM »
I need help in identifying the molecule

Offline Babcock_Hall

  • Chemist
  • Sr. Member
  • *
  • Posts: 5262
  • Mole Snacks: +303/-22
Re: nmr interpretation
« Reply #4 on: May 09, 2018, 05:32:25 PM »
It is a forum rule that you must show your attempt before we can help you.  What are your thoughts?

Offline wildfyr

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 1718
  • Mole Snacks: +191/-10
Re: nmr interpretation
« Reply #5 on: May 09, 2018, 09:20:03 PM »
That proton nmr is poorly phased. Secondly is this a real reaction where you synthesized something? If so, you should state the starting materials and desired product. It makes interpretation much easier. And it a forum rule that you must give us your attempt.

Offline wildfyr

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 1718
  • Mole Snacks: +191/-10
Re: nmr interpretation
« Reply #6 on: May 09, 2018, 09:21:38 PM »
Looking again, I don't think this nmr is locked. The peaks are in an unusually downfield part of the spectrum, and poorly resolved. It's in cdcl3 and I see no clean cdcl3 singlet.

Offline hypervalent_iodine

  • Chemist
  • Full Member
  • *
  • Posts: 261
  • Mole Snacks: +33/-1
Re: nmr interpretation
« Reply #7 on: May 09, 2018, 09:26:48 PM »
Looking again, I don't think this nmr is locked. The peaks are in an unusually downfield part of the spectrum, and poorly resolved. It's in cdcl3 and I see no clean cdcl3 singlet.

Look at the carbon. I don't think that's CDCl3. Looks like someone locked to the wrong solvent. Maybe CD3OD?

Offline AMARACHUKWU

  • Regular Member
  • ***
  • Posts: 10
  • Mole Snacks: +0/-0
Re: nmr interpretation
« Reply #8 on: May 10, 2018, 06:17:02 AM »
That proton nmr is poorly phased. Secondly is this a real reaction where you synthesized something? If so, you should state the starting materials and desired product. It makes interpretation much easier. And it a forum rule that you must give us your attempt.
this is a product I got from the isolation of camwood extract. (Baphia nitida) using the traditional column.

Offline hypervalent_iodine

  • Chemist
  • Full Member
  • *
  • Posts: 261
  • Mole Snacks: +33/-1
Re: nmr interpretation
« Reply #9 on: May 10, 2018, 06:32:30 AM »
That proton nmr is poorly phased. Secondly is this a real reaction where you synthesized something? If so, you should state the starting materials and desired product. It makes interpretation much easier. And it a forum rule that you must give us your attempt.
this is a product I got from the isolation of camwood extract. (Baphia nitida) using the traditional column.

What solvent did you use to prepare the NMR sample?

Offline AMARACHUKWU

  • Regular Member
  • ***
  • Posts: 10
  • Mole Snacks: +0/-0
Re: nmr interpretation
« Reply #10 on: May 10, 2018, 06:50:41 AM »
What solvent did you use to prepare the NMR sample?
chloroform

*MOD EDIT - monster quote*
« Last Edit: May 10, 2018, 05:01:52 PM by Arkcon »

Offline wildfyr

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 1718
  • Mole Snacks: +191/-10
Re: nmr interpretation
« Reply #11 on: May 10, 2018, 09:04:47 AM »
I have trouble believing there is no alkyl content to this molecule as is implied by the NMR. Thats why I suspect its poorly locked. It just looks like a generally poorly taken NMR. Try asking someone who is experienced in using it to lock and shim it. Also... when you say chloroform, you mean CDCl3 right?

Offline AMARACHUKWU

  • Regular Member
  • ***
  • Posts: 10
  • Mole Snacks: +0/-0
Re: nmr interpretation
« Reply #12 on: May 10, 2018, 03:11:02 PM »
*MOD EDIT - monster quote*
yes. i just spoke with the lab where the analysis was done and they said thats the much they can do.
« Last Edit: May 10, 2018, 05:00:48 PM by Arkcon »

Offline wildfyr

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 1718
  • Mole Snacks: +191/-10
Re: nmr interpretation
« Reply #13 on: May 10, 2018, 03:30:02 PM »
I just can't get your proton, carbon, and IR to jibe. Proton shows broad, polymer-like peaks, all above 5. Carbon shows a bunch of clean singlets, and only about half of them are in the aryl. FTIR shows a peak at 2952 cm-1 which indicates alkyl content, but no carbonyl is seen. However the carbon shows what looks like an ester at 175ppm.

My definitive response to the claim that no one screwed up is that there is no triplet at 77.2 ppm on the 13C NMR, which is characteristic of CDCl3. So ask them to run it again, and this time not be lazy jerks and actually lock and shim it.

Offline AMARACHUKWU

  • Regular Member
  • ***
  • Posts: 10
  • Mole Snacks: +0/-0
Re: nmr interpretation
« Reply #14 on: May 10, 2018, 03:34:08 PM »
 thank you. i will tell them to run it again and get back with thr results

*MOD EDIT - monster quote*
« Last Edit: May 10, 2018, 05:00:22 PM by Arkcon »

Sponsored Links