Mass Spectroscopy Elemental isotopic and molecular analyses. (March 2010)

2 Spectroscopy Mass Spectroscopy combined with IR and NMR are very powerful techniques in structure determination UV/Visible (older more limited information) spectroscopy is not used as much these days – the other techniques superseded it.

3 1) Mass spectroscopy. Lister and Renshaw (New Understanding Chemistry)

4 elemental analysis mass spec contd. – elemental analysis Lister and Renshaw (New Understanding Chemistry)

5 elemental analysis mass spec contd. – elemental analysis Lister and Renshaw (New Understanding Chemistry) e.g. for Neon… Note take care with s.f. Answer should b given in the same No of S.F. as was given in in the data.If data = and as well as and for the %’s then the answer would be If No of s.f. in data vary e.g and 22.0 then the answer is reported to the same s.f. as the least accurate data e.g i.e. answer is reported to 3 s.f. Note 3 s.f. is very common for A-level.

6 elemental analysis mass spec contd. – elemental analysis Mass spec revealed: No. of isotopes and can be used to calculate relative atomic mass Lister and Renshaw (New Understanding Chemistry)

7 MOLECULAR analysis mass spec contd. – MOLECULAR analysis Molecule fragmented next to the functional group !! MOLECULAR analysis

8 MOLECULAR analysis mass spec contd. – MOLECULAR analysis Lister and Renshaw (New Understanding Chemistry) Molecule can rearrange to produce exotic fragments once it ionizes/turns into a radical

9 MOLECULAR analysis mass spec contd. – MOLECULAR analysis In the M.S. shown, what name is given to the peak at m/z= 72? 43? Try and assign peaks at m/z= 29, 43, 57 and 72 What does the height of the peak tell us about the stability of the species? After, go back to slide 7 – Jim Clarke

10 MOLECULAR analysis mass spec contd. – MOLECULAR analysis m.s. of 2-Chloropropane

11 MOLECULAR analysis mass spec contd. – MOLECULAR analysis – Jim Clarke

12 MOLECULAR analysis mass spec contd. – MOLECULAR analysis

13 MOLECULAR analysis mass spec contd. – MOLECULAR analysis

14 MOLECULAR analysis mass spec contd. – MOLECULAR analysis

15 MOLECULAR analysis mass spec contd. – MOLECULAR analysis

16 MOLECULAR analysis mass spec contd. – MOLECULAR analysis

17 MOLECULAR analysis mass spec contd. – MOLECULAR analysis (single nucleus) Aromatic m.s. of Benzaldehyde

18 MOLECULAR analysis mass spec contd. – MOLECULAR analysis (again) m.s. of Napthalene

19 MOLECULAR analysis mass spec contd. – MOLECULAR analysis

20 MOLECULAR analysis mass spec contd. – MOLECULAR analysis

21 MOLECULAR analysis mass spec contd. – MOLECULAR analysis Deduce the molecule and assign labeled peaks A,B,C and D

22 MOLECULAR analysis mass spec contd. – MOLECULAR analysis Clue?...This organic compound contains at least one halogen.

23 MOLECULAR analysis mass spec contd. – MOLECULAR analysis Clue: Molecule not featured earlier. The empirical formula is C 2 H 3 O 1

24 MOLECULAR analysis mass spec contd. – MOLECULAR analysis That’s all folks !!!