Question

Use the mass spectrum to answer the questions below

1. Does the compound contain chlorine or bromine or neither? Explain.
2. Give the m/z value for the molecular ion peak.
3. Give the m/z value for the base peak.
4. The base peak is a common fragment – what is the most likely chemical formula for the base peak?
5. Does the compound contain chlorine or bromine or neither? Explain.
6. Give the m/z value for the molecular ion peak.
7. Give the m/z value for the base peak.
8. An alkyl group was lost from the molecular ion to give the species that is circled on the spectrum. Which alkyl group was lost?

100 HS-N-0069 80 60 40 20 C 25 50 75 100 125 m/z Relative Intensity - 100 MS2015-05121CW 80 60 40- 20 0uttrt 25 50 75 100 125 175 m/z aTsuaauI ATaTo

Answer 1

1) a) M+ ion peak is at 126 and M+2 is at 128 with ratio of 3:1 Thus the peaks are conformation of presence of Cl atom as the relative abundance is 35CI is 100% and 37CI is 32.5% The molecule contains Cl atom b) Molecular ion peak m/z = 126 c) Base peak m/z = 91 d) As the base peak is 91, it is most likely corrosponding to tropylium ion. This peak results due to loss of hydrogen or methyl group of alkyl substituted benzene ring present in the molecule 2) e) M+ ion peak is at 178 and M+2 peak at 180 with ratio of almost 1:1 This is characteristic ratio found in bromine containing compound due to relative abundance of 79Br is 100% and 81 Br is 98%. Thus molecule contains Br atom f) Molecular ion peak m/z = 178 g) Base peak m/z h) 178-149 29 this is corrosponding to ethyl group. Thus the alkyl group lost in the fragmentation is ethyl group. 137