Before spectroscopy was invented...
a) Draw the structures of these two isomers.
b) A turn of the 20th century chemist isolated an aromatic compound...
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Xylene is a disubstituted benzene with methyl groups on the ring. Ortho-xylene, therefore, is composed of a benzene ring with methyl groups on positions 1 and 2 of the ring. In other words, the two methyl groups are side by side.
Therefore, when you add one nitrate group, NO2, two possible isomers can form. Let's just keep the numbering system we started above, i.e. that the 2 methyl groups are on carbons 1 and 2. Therefore, one isomer could have nitrate group on carbon 3 or carbon 6. Either way, it would look the same. Draw them out so that you can see this.
The other isomer would have the nitrate group on either carbons 4 or 5. Either way, those compounds would look the same.
Therefore, the two isomers formed are 1,2-dimethyl-3-nitrobenzene
See the attached file for ...
The solution involves explanations for how compounds were determined before spectroscopy was invented, along with calculations for determining a compound with spectroscopy.