So the product is 1,2-dimethoxy-4-nitrobenzene, consistent with the melting point.
The melting point of the semicarbazide derivative of compound A was found to be 224-225 C, which means that compound A is likely to be o-chloro-benzaldehyde or p-hydroxy-benzaldehyde. According to the 1HNMR spectrum, with benzene proton peaks around 7 ppm and aldehyde proton singlet, the second functional group should also contain one proton, showing up as a singlet. Therefore, the second functional group is a hydroxy-group, so compound A is p-hydroxy-benzaldehyde. This hydroxyl-group also gives the possibility to from the bicyclic structure of compound B.
The H atom of NH will exchange with solvent, so if D2O is added it may be replaced with D. This only influences the peak of the H of NH, which will become a doublet with the second peak (of D) at lower intensity and at higher field (lower ). ...Show more