To identify the unknown compound X, we will first analyze the given information and then deduce the possible structure based on the fragmentation pattern observed in the mass spectrum.Given information:1. Molecular formula: C8H10O22. Molecular ion peak M+ at m/z 1503. Base peak at m/z 77The molecular ion peak at m/z 150 confirms the molecular formula of the compound as C8H10O2. Now, let's analyze the base peak at m/z 77.A base peak at m/z 77 is characteristic of a benzyl cation C7H7+ . This suggests that the compound has a benzyl group attached to it. Since the molecular formula is C8H10O2, the remaining part of the molecule should be CH3O2 methoxy group . Combining the benzyl group and the methoxy group, we can deduce the structure of the compound as follows:The structural formula of the compound X is: O "C6H5 - CH2 - O - CH3This compound is known as Benzyl methyl ether.Now, let's explain the fragmentation pattern observed in the mass spectrum. The base peak at m/z 77 is formed by the cleavage of the C-O bond between the benzyl group and the methoxy group. This generates a stable benzyl cation C7H7+ and a methoxy radical CH3O . The benzyl cation is responsible for the base peak at m/z 77, while the molecular ion peak at m/z 150 corresponds to the intact compound.In summary, the unknown compound X is Benzyl methyl ether, and its fragmentation pattern in the mass spectrum can be explained by the cleavage of the C-O bond between the benzyl and methoxy groups, generating a stable benzyl cation and a methoxy radical.