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Problem: An unknown organic compound with the molecular formula C3H8O shows a molecular ion peak (M+) at m/z = 60 in its mass spectrum. It also shows a prominent fragment peak at m/z = 45. Determine the probable structure and explain the fragmentation. Step 1: Calculate the total molecular mass from the formula C3H8O to verify the molecular ion peak. Mass of Carbon = 3 * 12 = 36, Hydrogen = 8 * 1 = 8, Oxygen = 1 * 16 = 16. Total mass = 36 + 8 + 16 = 60 g/mol, which matches the M+ peak at m/z = 60. Step 2: Analyze the fragment peak at m/z = 45. Find the difference between the molecular ion and the fragment: 60 - 45 = 15. Step 3: Identify the lost piece of mass 15. A mass of 15 corresponds to a methyl group (-CH3, since Carbon=12 + 3 Hydrogens=3). Step 4: Propose the structure. The compound starts as CH3CH2CH2OH (propan-1-ol) or CH3CH(OH)CH3 (propan-2-ol). Losing a -CH3 group from the end leaves behind a fragment of mass 45, which corresponds to [CH3CH2O]+ or [CH(OH)CH3]+. Step 5: Conclude structure elucidation. The presence of these specific masses confirms it is an aliphatic alcohol with a straight or branched three-carbon chain.