Practice Questions for Mass Spectrometry
Question 1:
While running a new reaction, a chemist notices the evolution of a gas. A sample of this gas gave a mass spectrum in which the molecular ion (m/z = 44) was the largest ion peak. The only other significant peaks were observed at m/z = 28 & m/z = 16. What is this gas?
| Enter a formula (without subscripting numbers) or a name in the answer box. | Hint: Consider the mass differences between these ions. |
Question 2:
A liquid compound gave a mass spectrum showing a strong molecular ion
at m/z = 156. The only fragment ions are seen at m/z = 127 & 29.
Suggest a structure for this
compound.
| Enter a formula (without subscripting numbers) or a name in the answer box. | Hint: Consider the mass differences between these ions. |
If you don't know the entire structure but would like to propose a fragment to verify that you are on the right track, fill in the fragment or fragments below:
Fragment ion mass 29:
Fragment ion mass 127:
Question 3:
A liquid compound gave a mass spectrum in which the molecular ion
appears as a pair of equal intensity peaks at m/e = 122 & m/z = 124.
Small fragment ion peaks are seen at m/z = 107 & 109 (equal intensity),
and at m/z = 79, 80, 81, & 82 (all roughly the same size). Large fragment
ions are seen at m/z = 43 (base peak), 41 & 39.
Suggest a name for this compound.
| Enter a name in the answer box. | Hints: What element is indicated by equal intensity ions
differing by 2 amu? What mass remains if the isotopic mass of this element is subtracted from the molecular ion mass? |
If you don't have a final answer but would like to verify that you are on the right track, fill in the fragment or element below:
An element having equal intensity isotopic ions differing by 2 amu:
Remaining mass after subtraction of that element's mass (enter a number):