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Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: SpectroKid1 on October 06, 2014, 05:14:24 PM
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Hi guys
As part of my degree I have to do a spectroscopy course which includes identifying organic compounds from their spectra.
I'm a little stuck so was hoping for some advice
Here's the spectra i have http://imgur.com/a/MkPvt
So from the DEPT 13C NMR i inferred the the 3 or 4(?) peaks at the left hand side of the spectra are quaternary carbons. The peak at ~77 is due to the solvent CDCl3. The peak at 0 is due to TMS
The IR, i thought the band at 3000 was due to an aromatic compound. But other than that i'm stumped
From the Mass Spec. Even Mass indicated even number of Nitrogen atoms. Absence of any M+2 peaks shows no Br, S or Cl. I was really confused by the lack of any sort of alkane branches. I thought maybe the loss of 31 came from lost of an alcohol group? Also, using the relative abundance of the M+1 peak as being ~9% I used the relative abundance of 13C (1.1) to calculate there are 8 carbons in the structure
Any help is greatly appreciated
Thanks
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Well, the 3600 cm-1 band tells you there's OH there. Given that, juggling with the numbers to get 112 suggests perhaps fluorophenol - the simplicity of the nmr would suggest para.
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Well, the 3600 cm-1 band tells you there's OH there. Given that, juggling with the numbers to get 112 suggests perhaps fluorophenol - the simplicity of the nmr would suggest para.
Excellent! I thought it might be some kind of phenol but kept blanking out on the 19 m/z I was missing. Would you be able to give me a hand on a couple more, if you don't mind?
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I can try; I promise nothing.
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I can try; I promise nothing.
Hi again
Could you have a look at this please?
http://imgur.com/a/oVNYe
Strong IR band at ~1700 indicates presence of carbonyl oxygen. In a Spectroscopy book I've got from the library, the band at ~1200 is supposedly indicative of a saturated ester. The band at ~2900 also suggests an ester
In the mass spec. The molecular ion peak is 154, with an M+2 showing a +2 isotope is present. The 3:1 peak ratio shows its Chlorine due to the 75:25 relative abundances of 35Cl& 37Cl. The peak at 118 is indicative of loss of HCl
There is a peak at 43 which I thought what a C-H group with two methyl groups and a C=O group attached. This is because there is a multiplet peak in the 1H NMR with 7 peaks and an integration of 1. So that would come from the H atom coupling to the two equivalent methyl groups.
The 13C NMR shows which environments are CH3, CH2, CH and quaternary C environments.
This is what I've got so far, so any help would be great
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This has got me stumped. Are you certain that 154 is the molecular ion?
I'm virtually certain there's an isobutyl group; (CH3)2CH-CH2- is consistent with the fragment 57 (and 43), and with the NMR. Likewise, 63/65 is consistent with COCl, and the frequency of ca. 1800 cm-1 is consistent with an acid chloride. The band at ca. 1200 must be C-O or C-F. But how to fit them together, and make up a MW of 154, I can't see.
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This has got me stumped. Are you certain that 154 is the molecular ion?
I'm virtually certain there's an isobutyl group; (CH3)2CH-CH2- is consistent with the fragment 57 (and 43), and with the NMR. Likewise, 63/65 is consistent with COCl, and the frequency of ca. 1800 cm-1 is consistent with an acid chloride. The band at ca. 1200 must be C-O or C-F. But how to fit them together, and make up a MW of 154, I can't see.
I think 154 is the molecular ion, given the evidence that there's Cl there, that's the only thing that makes sense for a Mass.
I agree with the isobutyl group, and the C=O. I was thinking that maybe it was an eater and then an alkyl halide, is there anything that suggests this isn't the case?
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Carbonyl frequency looks too high for an ester, C-O too high for an ether. Can you get a hemicarbonate chloride (dunno what the proper name would be) RO-CO-Cl?
Still have a problem getting 154/6. Are you sure that's the highest? How far up was the MW search extended?
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Carbonyl frequency looks too high for an ester, C-O too high for an ether. Can you get a hemicarbonate chloride (dunno what the proper name would be) RO-CO-Cl?
Still have a problem getting 154/6. Are you sure that's the highest? How far up was the MW search extended?
Everything that I've been given is what's attached in that post. I'm struggling to make it fit 154 too. I wouldn't worry about it though. I'll keep chipping away
If you could check this for me, that would be great
I think this is Benzaldehyde: http://imgur.com/a/uJCEf
C=O band in the IR, 1H peak at 10ppm aromatic carbons and a quaternary aromatic carbon too. Would you agree?
If Benzaldehyde is compound 1, compound 2 is a product of a reaction of compound 1 (if that makes sense) I can't figure out what it is. Here's the spectra i've got: http://imgur.com/a/fnpM1
So far I've got: must contain nitrogen, as the mass number is odd. The Aldehyde peak has disappeared from the 1H NMR so that suggests the reaction has occurred at the aldehyde site
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Carbonyl frequency looks too high for an ester, C-O too high for an ether. Can you get a hemicarbonate chloride (dunno what the proper name would be) RO-CO-Cl?
Still have a problem getting 154/6. Are you sure that's the highest? How far up was the MW search extended?
A chloroformate. 154/6 might be isobutyl chloroformate + water. Could that be an artefact of MS? I don't know enough about EI to be sure, but maybe if there's water in the system you could see isobutyl carbonic acid.HCl.
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Carbonyl frequency looks too high for an ester, C-O too high for an ether. Can you get a hemicarbonate chloride (dunno what the proper name would be) RO-CO-Cl?
Still have a problem getting 154/6. Are you sure that's the highest? How far up was the MW search extended?
A chloroformate. 154/6 might be isobutyl chloroformate + water. Could that be an artefact of MS? I don't know enough about EI to be sure, but maybe if there's water in the system you could see isobutyl carbonic acid.HCl.
I suspect you might be right. The carbon and hydrogen nmrs match what I would expect from that compound. Cheers for that! Any help with the benzaldehyde spectra in the post above?
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1 is benzaldehyde. For 2, I can think of a handful of things that would match 149, e.g. PhCONMe2, but not without introducing hydrogens that ought to appear in the IR and NMR, but don't.
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1 is benzaldehyde. For 2, I can think of a handful of things that would match 149, e.g. PhCONMe2, but not without introducing hydrogens that ought to appear in the IR and NMR, but don't.
That's where my confusion is coming from too. Obviously the aldehyde is the reaction site as the 10ppm 1H peak disappears. The only new Hydrogen environment that appears is the double with an integration of 1 at ~8ppm.
Here's the spectra for compound 3 and 4, so it might be possible to work backwards, since the reaction is 1->2->3->4
Unknown 3: http://imgur.com/a/tLYtK
Unknown 4: http://imgur.com/a/Di4EV
These seem to indicate more significant changes to the compound
Also, i realised where the extra mass was coming from from the fact NH3 was used as the ionising gas, so there was an M+NH4 adduct in the spectra, hence +18
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Carbonyl frequency looks too high for an ester, C-O too high for an ether. Can you get a hemicarbonate chloride (dunno what the proper name would be) RO-CO-Cl?
Still have a problem getting 154/6. Are you sure that's the highest? How far up was the MW search extended?
A chloroformate. 154/6 might be isobutyl chloroformate + water. Could that be an artefact of MS? I don't know enough about EI to be sure, but maybe if there's water in the system you could see isobutyl carbonic acid.HCl.
I suspect you might be right. The carbon and hydrogen nmrs match what I would expect from that compound. Cheers for that! Any help with the benzaldehyde spectra in the post above?
I think the M+18 peak arises because NH3 is used as the ionising gas, so there will be an M +NH4+ ion peak.
Could you take a look at the benzaldhye reaction sequence sectra?
Benzaldehyde -> 2 -> 3 -> 4
2: http://imgur.com/a/fnpM1
3: http://imgur.com/a/tLYtK
4: http://imgur.com/a/Di4EV
Any ideas on what these could be?
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I've been off sick for a while but I'll look at these when I've time. In the meantime:
Do you know what the reagents were?
Can you annotate the IR spectra with the frequencies of the major peaks? It's hard to read them off to better than 50-100 cm-1.
If you're going to post any more of these, please take care when scanning to get the original as flat as possible to avoid the plots appearing curved.
Did you run these spectra, or were you just given them? Better quality IR spectra, without all those negative peaks, would help.
Should I expect a M+NH4 peak in every MS? (I'm not an MS expert.)
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I've been off sick for a while but I'll look at these when I've time. In the meantime:
Do you know what the reagents were?
Can you annotate the IR spectra with the frequencies of the major peaks? It's hard to read them off to better than 50-100 cm-1.
If you're going to post any more of these, please take care when scanning to get the original as flat as possible to avoid the plots appearing curved.
Did you run these spectra, or were you just given them? Better quality IR spectra, without all those negative peaks, would help.
Should I expect a M+NH4 peak in every MS? (I'm not an MS expert.)
Hi, I hope you're feelings better soon!
In answers to your questions:
I don't know the reagents, only that 1->2->3->4
I don't have more accurate peak data for the IR, only the spectra as photographed, I can approximate some of the major peaks if that would help, but it will only be to a similar accuracy as to you can do
Sorry about the issues with the photos, if there are any in particular that you'd like to be clearer let me know and I can redo them
I didn't run these spectra, I was just given them. I'm very frustrated with the quality of the spectra, the nmr is poorly resolved and the IR has a lot of spurious peaks. I'll be complaining about this when I speak to someone at the university.
Nope, don't expect a M+NH4 peak in the mass spec, that was only for number 2, as it specifically stated on the mass spec, but I had overlooked it at the time.
As always, any help you can provide is hugely appreciated! Once again, hope you're feeling better soon
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Should I expect a M+NH4 peak in every MS?
Under CI (NH3) conditions,
if the gas phase basicity of NH3 is higher than that of M, you will generally see [M+NH4]+, while
if the gas phase basicity of NH3 is lower than that of M, you will generally see [M+H]+.
Under ESI (NH4OAc) conditions, you will generally see both [M+H]+ and [M+NH4]+; in fact the characteristic mass shifts of +17 (NH3), +22 (Na) and +38 (K) relative to [M+H]+ are used to confirm the MW.
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This is perplexing. The NMR of compound 4 (apart from a lone proton) looks very similar (but not identical) to the one given by Aldrich for 2-tetralone. But the MW is high (unless M+ is just absent for some reason) and where is the OH that the IR suggests is there? (Unless the sample is just wet of course.) But I don't see how this comes from benzaldehyde, or what 2 and 3 are.
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SpectroKid1,
There are several rules associated with using this forum.
1. We are not supposed to solve homework problems---merely nudge you in the right direction.
2. You are shooting yourself (and us) in the foot by not disclosing ALL of the analytical information. For example, it is vitally important to know the ionizing conditions used to generate the MS data (see my post of Oct. 18) right at the outset. You have also failed to take advantage of the C & H %-composition data provided on the mass spectrum.
That said, you are at least putting effort into the problems (which is nice to see) and are generally getting somewhere---but the devil is in the details, so tighten up your observational skills (point 2, above). Do not be discouraged---no one of us was born knowing this spectral interpretation---it does have to be learned the hard way.
3. The MS data for cpd. 2 contains some VERY characteristic m/z signals !!! You need to consider the structure and reactions of benzaldehyde, as well as doing some reading on MS interpretation (see Interpretation of Mass Spectra by McLafferty & Frantisek).
Good Luck !
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This is perplexing. The NMR of compound 4 (apart from a lone proton) looks very similar (but not identical) to the one given by Aldrich for 2-tetralone. But the MW is high (unless M+ is just absent for some reason) and where is the OH that the IR suggests is there? (Unless the sample is just wet of course.) But I don't see how this comes from benzaldehyde, or what 2 and 3 are.
Is it possible than the benzaldhye could react with an Azide (N3) and H+ to form a PhC(O)N3H type structure?
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SpectroKid1,
There are several rules associated with using this forum.
1. We are not supposed to solve homework problems---merely nudge you in the right direction.
2. You are shooting yourself (and us) in the foot by not disclosing ALL of the analytical information. For example, it is vitally important to know the ionizing conditions used to generate the MS data (see my post of Oct. 18) right at the outset. You have also failed to take advantage of the C & H %-composition data provided on the mass spectrum.
That said, you are at least putting effort into the problems (which is nice to see) and are generally getting somewhere---but the devil is in the details, so tighten up your observational skills (point 2, above). Do not be discouraged---no one of us was born knowing this spectral interpretation---it does have to be learned the hard way.
3. The MS data for cpd. 2 contains some VERY characteristic m/z signals !!! You need to consider the structure and reactions of benzaldehyde, as well as doing some reading on MS interpretation (see Interpretation of Mass Spectra by McLafferty & Frantisek).
Good Luck !
Hi
I'm not looking for people to do my work, just to show me where to go, as for compound 2, 3 & 4 I've no idea where I'm going. For 2 the mass increase, but theres no new carbon environments and nothing particularly characteristic in the Hydrogen NMR.
Is it possible that it could be Ph-C(O)N3H, like an Azide attached to the carbonyl carbon? But then you'd expect a carbon slightly further downfield than we're seeing
I am providing you with all the information I have. I've attached all the spectra I've been given, there's nothing missing
What peaks should I be looking for? The one at 91 is presumably C7H7?
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Yes, m/z 91 is C7H7+!!!!!!!!!!!, VERY characteristic of substd. phenyl.
What other low m/z signal signifies benzene ring ??
Let me give you a nudge, by telling you that m/z 149 does NOT contain nitrogen. m/z 149 is VERY VERY characteristic of a certain class of organic plasticizer. Once seen, never forgotten !!
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Yes, m/z 91 is C7H7+!!!!!!!!!!!, VERY characteristic of substd. phenyl.
What other low m/z signal signifies benzene ring ??
Let me give you a nudge, by telling you that m/z 149 does NOT contain nitrogen. m/z 149 is VERY VERY characteristic of a certain class of organic plasticizer. Once seen, never forgotten !!
Are you talking about Phthalates? I found one with Mass 149 ( http://i.imgur.com/QLEiR8A.png ), but it doesn't fit with the carbon or the hydrogen NMR structures that I have provided. There are too few Carbon environment in the phthalate structure, compared to the NMR spectra I have provided, there are also too few hydrogen environments too. Also, I'm not sure how, or if you can go directly from a benzaldehyde to that structure?
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I've been working on compound 3 and I now think it's phenylethylamine, can anyone check this? Not sure how I would go from Benzaldehyde-> X-> Phenylethylamine though?
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2-phenylethylamine or N-phenylethylamine?
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2-phenylethylamine or N-phenylethylamine?
N-phenylethyleamine: Ph-(CH2)2NH2
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That's 2-phenylethylamine
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That's 2-phenylethylamine
Well in that case I think Compound 3 is 2-phenylethylamine. Do you agree?
Out of curiosity, what is the structure of n-phenylamine? I though N- was the prefix denoting a straight chain molecule, i.e n-BuLi which is a straight Butane chain with an anion
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n- denotes a straight chain. N- denotes a group attached to nitrogen. N-phenylethylamine would be PhNHCH2CH3. 2-phenylethylamine would be more consistent with the nmr suggesting 2 CH2 groups.
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n- denotes a straight chain. N- denotes a group attached to nitrogen. N-phenylethylamine would be PhNHCH2CH3. 2-phenylethylamine would be more consistent with the nmr suggesting 2 CH2 groups.
Thanks
Ok, so i think i've solved the sequence
Benzaldehyde -> B-Nitrostyrene -> Phenylethylamine -> Tetrahydroisoquinoline
The one thing I'm missing is reagents.
For 1->2 i'm guessing a base and nitromethane
2->3 possible Hydrogen and palladium on a carbon support
3->4 I'm not sure
Any chance you have an idea of the reagents/conditions required to carry out the reactions?
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Benzaldehyde -> B-Nitrostyrene -> Phenylethylamine -> Tetrahydroisoquinoline
The one thing I'm missing is reagents.
For 1->2 i'm guessing a base and nitromethane
2->3 possible Hydrogen and palladium on a carbon support
These sound good
3->4 I'm not sure
This is a classic named reaction, and is a stepwise combination of two common reactions I'm sure you'll have seen before. I'll give you a hint: You need to add a CH2 between the N and the Ph groups. What kind of reactivity do amines and alkyl-substituted arenes show - nucleophilic or electrophilic - and what sort of reactions do they participate in? Can you think of any appropriate C sources based on that?
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Benzaldehyde -> B-Nitrostyrene -> Phenylethylamine -> Tetrahydroisoquinoline
The one thing I'm missing is reagents.
For 1->2 i'm guessing a base and nitromethane
2->3 possible Hydrogen and palladium on a carbon support
These sound good
3->4 I'm not sure
This is a classic named reaction, and is a stepwise combination of two common reactions I'm sure you'll have seen before. I'll give you a hint: You need to add a CH2 between the N and the Ph groups. What kind of reactivity do amines and alkyl-substituted arenes show - nucleophilic or electrophilic - and what sort of reactions do they participate in? Can you think of any appropriate C sources based on that?
I've had look around the web & literature. Is it a Pictet-Spengler reaction? I actually haven't came across this so far in my degree, hence I didn't recognise it. Given it used Aldehydes and acid for the reaction, I'd guess you need HCHO and a general inorganic acid like HCl?
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Is it a Pictet-Spengler reaction? I actually haven't came across this so far in my degree, hence I didn't recognise it. Given it used Aldehydes and acid for the reaction, I'd guess you need HCHO and a general inorganic acid like HCl?
Yes exactly. It's essentially an imine formation followed by an intramolecular Friedel-Crafts reaction.