Propose a reasonable structure of the molecule and briefly describe how you used

Question

Propose a reasonable structure of the molecule and briefly describe how you used the MS and the IR to come up with that structure. I need some help in understanding mass spectrometry to identify molecular formula. From the IR spectoscopy the compound has a c=o functional group, but I'm having trouble formulating a reasonable molecular formula from a parent peak 166m/z and base peak 87m/z.

An unknown organic molecule gives the following mass and IR spectra:

100 87 80 27 59 107 40 15 135 (166) 20 0 mt TTTTT TTT 40 TOTT 60TTTTTTTTTTTTT80 T 90nm10 TTTT110TTTTTTTTTTTTTTTTTTTTTT 40TTTTTTTTTTTTTTTTTTTT 17 m/z

Explanation / Answer

Hi,

In IR Spectrum the sharp peak around1700 cm-1 (between 1600-1700 indicates either amine or alkene) indicates the presence of carbonyl group (c=o).Now we need to narrow it down to which functional group is present.The large spectrum around

3000 cm-1 explains the compound formed is an acid.with the help of mass spectrometry we are able to identify the parent peak is 166.In mass spectrum the heaviest ion (the one with greates m/z value)is to be the molecular ion.Because the largest value is 166 that represents the largest ion going through the mass spectrometer and you can assume that this is the largest molecular ion with the relative formula mass of the compound 166.with this mass we come to an understanding that there are teriphthalic acid,isopthalic acid and dimethy arsinic cid.By comparing the three graphs we come to an understnding that the graphs fulfills the criteria of Terephthalic acid whose formula is (C8H6O4).The broken lines before and after base peaks are fragmentation of the compound nd differs for each compound.

Ans : Terephthalic acid

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