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Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: jestquim on February 17, 2021, 12:57:05 PM

Title: Determine the structure of an organic compound from its mass spectrum.
Post by: jestquim on February 17, 2021, 12:57:05 PM
We know that the mass spectrum of compound A, whose empirical formula is C5H6O, is as follows:

(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2FC5H6O.png&hash=9b5c92117d11bd59df5b09f14a870bb3)

From the spectrum, I know that the molecular mass is approximately 80 g/mol. But little else. Could the structure be deduced from this data?
Title: Re: Determine the structure of an organic compound from its mass spectrum.
Post by: AWK on February 17, 2021, 01:44:05 PM
You can suggest a sensible structure. But it takes some work.
Title: Re: Determine the structure of an organic compound from its mass spectrum.
Post by: jestquim on February 17, 2021, 02:52:09 PM
You can suggest a sensible structure. But it takes some work.

What strategy should I follow to be able to do so? For example, in NMR spectroscopy I look at the chemical shift, but here I don't know what to base it on. As I said the only thing I know, for the moment, is the molecular weight and the degree of unsaturation, which is three.
Title: Re: Determine the structure of an organic compound from its mass spectrum.
Post by: AWK on February 17, 2021, 05:01:26 PM
In mass spectrometry, we start with the analysis of the summary formula, e.g. C6H6 can be an aliphatic compound with 4 double bonds (see eg formula proposed for benzene by Archibald. S. Couper in 1858), a ring compound (1 ring) with three double bonds, etc.

Then we match the mass ions from our spectrum to the probable structures from our summary formula analysis using the fragmentation laws of mass spectrometry.
It takes a lot of hard work to start with.

And then it will take you a few seconds to decode such a simple mass spectrum. Once you have a reasonable structure proposal, you can compare it with the spectra in the databases.
Title: Re: Determine the structure of an organic compound from its mass spectrum.
Post by: kriggy on March 04, 2021, 04:57:49 AM
The structure can be deduced from the spectra.

https://www.youtube.com/watch?v=FCCFiyoDTaM&ab_channel=Knowbee

this might be usefull for you to watch
Title: Re: Determine the structure of an organic compound from its mass spectrum.
Post by: Babcock_Hall on March 04, 2021, 08:41:56 AM
Did you calculate the degrees of unsaturation?