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Topic: Structure Prediction for unknown compounds  (Read 17336 times)

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Offline AWK

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Re: Structure Prediction for unknown compounds
« Reply #15 on: March 13, 2007, 02:24:55 PM »
Probably I was mistaken - CH2CHO should show coupling. There was now coupling with -CHO group
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Offline Dolphinsiu

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Re: Structure Prediction for unknown compounds
« Reply #16 on: March 14, 2007, 11:18:34 AM »
o..Actually I don't understand NMR very much!

Then what is the actual correct answer??Is my answer really correct?
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Offline AWK

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Re: Structure Prediction for unknown compounds
« Reply #17 on: March 14, 2007, 11:40:17 AM »
Very often only elemental analysiss and NMR data are insufficient to get the full structure. Just check in tables for your possible structures and take this one with the closest chemical shifts to your data.
The tentative possibilites are, eg:
-CH2Cl -CH2CH2N(CH3)2 and -CHO with C6H3
or -CH2N(CH3)2 -CH2CH2Cl and -CHO with C6H3
or -Cl-, -CH2CH2N+(CH3)2CH2-(condensed ring) and -CHO with C6H3
Multiplicity for H aromatic may suggest 1,2,3 substitution of ring in any case
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Offline Dolphinsiu

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Re: Structure Prediction for unknown compounds
« Reply #18 on: March 14, 2007, 11:47:50 AM »
So many possible structures, is it possible for 1,2,4 and 1,3,4 substitution in aromatic ring (C6H3) ??

Also as fragmentation involved is 51, -CH2Cl is being isolated from the cpd

Can I say that the only possible structure is

-CH2N(CH3)2 -CH2CH2Cl and -CHO with C6H3 where site of subsitution can be 1,2,3,1,2,4 and 1,3,4?
« Last Edit: March 14, 2007, 12:19:39 PM by Dolphinsiu »
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Offline AWK

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Re: Structure Prediction for unknown compounds
« Reply #19 on: March 14, 2007, 01:50:26 PM »
Compare your suggestion to possibility of coupling constants of hydrogens in different thrice substituted benzenes
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Offline Dolphinsiu

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Re: Structure Prediction for unknown compounds
« Reply #20 on: March 15, 2007, 01:50:27 PM »
But there is no coupling constant provided in this problem. Is there more possibility in structure diversity in unknown cpd (I) due to deficient information?
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Offline AWK

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Re: Structure Prediction for unknown compounds
« Reply #21 on: March 15, 2007, 02:58:43 PM »
It does not matter numbers are missing. But you have information such as: singlet, triplet, multiplet - this is information on possible couplings
« Last Edit: March 16, 2007, 02:08:28 AM by AWK »
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Offline mir

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Re: Structure Prediction for unknown compounds
« Reply #22 on: March 15, 2007, 05:12:43 PM »
I made a chart over the losses in the MS-spectra. I hope it helps. It is a diagonal matrice, that represent all possible ways of losses.
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Offline mir

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Re: Structure Prediction for unknown compounds
« Reply #23 on: March 15, 2007, 05:22:06 PM »
Have you thought about saturated aliphatics? The formula (CnH2n+1)+, seems to fit quite well with the ions.
« Last Edit: March 15, 2007, 05:35:43 PM by mir »
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No single thing abides, but all things flow.
Fragment to fragment clings, and thus they grow
Until we know and name them.
Then by degrees they change and are no more
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Offline Dolphinsiu

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Re: Structure Prediction for unknown compounds
« Reply #24 on: March 16, 2007, 07:41:26 AM »
Do you mean that

-Cl-, -CH2CH2N+(CH3)2CH2-(condensed ring) and -CHO with C6H3

or -CH2Cl-, -CH2N+(CH3)2CH2-(condensed ring) and -CHO with C6H3


are the most possible structure for cpd (I) ?
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Offline AWK

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Re: Structure Prediction for unknown compounds
« Reply #25 on: March 16, 2007, 09:50:24 AM »
I mean this two
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Offline Dolphinsiu

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Re: Structure Prediction for unknown compounds
« Reply #26 on: March 16, 2007, 01:00:22 PM »
o i see. I think the right hand side one is the most possible one as it satisfy MS(Mass spectrum)
The main fragmentation is
-CH3 (210)
-CHO (196)
-CH2Cl (176)
« Last Edit: March 16, 2007, 01:23:42 PM by Dolphinsiu »
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Offline Dolphinsiu

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Re: Structure Prediction for unknown compounds
« Reply #27 on: March 21, 2007, 10:03:44 AM »
Actually I want to confirm one more thing. Does the structure  -Cl-, -CH2CH2N+(CH3)2CH2-(condensed ring) and -CHO with C6H3 fit the fragmentation in mass spectrum?
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Offline AWK

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Re: Structure Prediction for unknown compounds
« Reply #28 on: March 22, 2007, 02:25:07 AM »
For condensed ring you probably do not find CH2Cl in MS spectrum
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