Question

Propose a molecular formula for a compound that exhibits the following peaks in its mass spectrum. (M)+· at m/z = 68, relative height = 100% (base peak). (M+1)+· at m/z = 69, relative height = 4.3%.

Answer 1

To determine the molecular formula of a compound with a given percent composition and molecular mass, we first calculate the empirical formula using the percent composition. Then we compare the empirical formula mass to the molecular mass to determine the molecular formula.

Step-by-step explanation:

To determine the molecular formula of a compound, we need to find the empirical formula first. We can use the percent composition and the molar mass to calculate the empirical formula. The percent composition of the compound is 49.47% carbon, 5.201% hydrogen, 28.84% nitrogen, and 16.48% oxygen.

Assuming we have a 100g sample of the compound, we can convert these percentages to moles: 49.47g C, 5.201g H, 28.84g N, and 16.48g O. Then we divide each mole value by the smallest mole value to get the ratios: C 1.0, H 12.1, N 4.1, O 2.8.

The empirical formula for the compound is C1H12N4O3. To determine the molecular formula, we need to compare the empirical formula mass to the molecular mass. The molecular mass is given as 194.2 amu. The empirical formula mass is the sum of the atomic masses: C 12.01 amu, H 1.008 amu, N 14.01 amu, O 16.00 amu. The empirical formula mass is 114.12 amu, which is smaller than the molecular mass. To find the molecular formula, we divide the molecular mass by the empirical formula mass: 194.2 amu / 114.12 amu = 1.70. We round this value to 2, which means the molecular formula is 2 times the empirical formula. Therefore, the molecular formula of the compound is C2H24N8O6.