An amino acid contains 52.2% carbon, 9.3% hydrogen, 8.7% nitrogen and 29.8% oxygen by mass and has a relative molecular mass of 161 g/mol. What is its molecular formula? What functional groups must it have?
In 100g of compound, the amount of each element is given by: C: n = 52.2/12 = 4.35 H: n = 9.3/1 = 9.3 N: n = 8.7/14 = 0.621... O: n = 29.8/16 = 1.8625 Dividing through by the smallest amount (0.621) gives: C: 7.0048..., H: 14.9758..., N: 1, O: 2.9991... These are all very close to whole numbers so the empirical formula is C7H15NO3. This has a relative formula mass of 161 so the molecular formula is also C7H15NO3. As this compound is stated to be an amino acid it must contain both an amine and a carboxylic acid group.
