Experiment 3 Mass Spectrometry

In this dry-lab, you must identify the unknown organic compound in your assigned mass spectrum, as well as identifying the listed fragments in the table.

All unknowns contain C and H, and may contain either N, O, Cl, or Br.

Unknowns cannot contain multiple different non-C/H atoms, but might contain two of the same non-C/H atoms.

i.e. an unknown cannot contain both O and Br, but could contain two Br atoms.

Fragments in your mass spectrum will be the result of breaking bonds in the parent unknown molecule. Formation of new bonds that were not present in the original compound is extremely rare.

The following isotopic ratios might be useful for analysing your spectrum:

Hydrogen: ¹H (100) : ²H (0.016) ²H can be completely neglected

Carbon: ¹²C (100) : ¹³C (1.11)

Nitrogen: ¹⁴N (100) : ¹⁵N (0.38) ¹⁵N can be completely neglected

Oxygen: ¹⁶O (100) : ¹⁷O (0.04) ¹⁷O can be completely neglected

Chlorine: ³⁵Cl (100) : ³⁷Cl (32.5)

Bromine: ⁷⁹Br (100) : ⁸¹Br (98)

Questions to ask as you work through your spectrum:

Do you have peaks at m/Z = 35 and 37 in a ~3:1 ratio?

If so, do you have three heavy peaks in a ~9:6:1 ratio?

Do you have peaks at m/Z = 79 and 81 in a ~1:1 ratio?

If so, do you have three heavy peaks in a ~1:2:1 ratio?

Do you have peaks at m/Z = 14 or 15? What organic fragments could these be? (hint: they do not contain nitrogen)

Identity of Assigned Unknown