Problem 1

A good starting point for structural determination is the molecular formula. Since no elemental analysis or high resolution mass spectrum is provided, we cannot determine it directly, but this is not necessarily an impediment to solve the structure. The few signals of the NMR spectra suggest that the molecule is small and, luckily, the mass spectrum provides valuable information. Indeed, the MS shows two peaks at m/z 122 and 124 with the same relative intensity that probably correspond to the molecular ion since they are the greatest m/z values in the spectrum, and the following ones respond to a loss of 15 mass units, usually the loss of a methyl group. The pattern consisting of two peaks of the same intensity differing by 2 mass units (M⁺ and M + 2) indicates that it is a monobrominated molecule. The presence of this medium-heavy atom whose isotopes,⁷⁹Br and⁸¹Br, are in a ratio of 51 : 49, would explain the molecular ions of the molecule. Moreover, the base peak at m/z 43 corresponds to the loss of bromine atom from the molecular ion and, therefore, supports our suspicion and confirms the small size of the carbon skeleton.