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2.12 Mass Spectroscopy

Elemental isotopic and molecular

analyses.(March 2010)

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Spectroscopy

Mass Spectroscopy combined with IR andNMR 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spectroscopy is not used as much these days the other techniques superseded it.

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1) Mass spectroscopy.

Lister and Renshaw (New Understanding Chemistry)

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mass spec contd.elemental analysis

Lister and Renshaw (New Understanding Chemistry)

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mass spec contd.elemental analysis

Lister and Renshaw (New Understanding Chemistry)

e.g. forNeon

Note take care with s.f. Answer should b given in the same No of S.F. as was givenin in the data.If data = 20.00 and 22.00 as well as 100.0 and 10.00 for the %s

then the answer would be 20.18.

If No of s.f. in data vary e.g 20.00 and 22.0 then the answer is reported to the sames.f. as the least accurate data e.g. 22.0 i.e. answer is reported to 3 s.f.

Note 3 s.f. is very common for A-level.

2018.201010010*22100*20

rA

heightpeakTotal

intensity)(orabundanceits*peakisotopeEachr

A

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mass spec contd.elemental analysis

Mass specrevealed: No. ofisotopes and can beused to calculate

relative atomicmass

Lister and Renshaw (New Understanding Chemistry)

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mass spec contd .MOLECULARanalysis

Lister and Renshaw (New Understanding Chemistry)

Molecule can rearrange to produce exotic fragmentsonce it ionizes/turns into a radical

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mass spec contd .MOLECULARanalysis

In the M.S. shown,what name is given

to the peak at m/z=72?

43?

Try and assignpeaks at m/z= 29,

43, 57 and 72

What does theheight of the peaktell us about thestability of thespecies?

After, go back to slide 7

www.chemguide.co.uk Jim Clarke

http://www.chemguide.co.uk/http://www.chemguide.co.uk/

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mass spec contd .MOLECULARanalysis

m.s. of 2-Chloropropane

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mass spec contd .MOLECULARanalysis

www.chemguide.co.uk Jim Clarke

http://www.chemguide.co.uk/http://www.chemguide.co.uk/

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mass spec contd .MOLECULARanalysis

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mass spec contd .MOLECULARanalysis

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mass spec contd .MOLECULARanalysis

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mass spec contd .MOLECULARanalysis

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mass spec contd .MOLECULARanalysis

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mass spec contd .MOLECULARanalysis

(single nucleus) Aromatic m.s. of Benzaldehyde

CHO

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mass spec contd .MOLECULARanalysis

(again) m.s. of Napthalene

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mass spec contd .MOLECULARanalysis

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mass spec contd .MOLECULARanalysis

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mass spec contd .MOLECULARanalysis

Deduce the moleculeand assign labeledpeaks A,B,C and D

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mass spec contd .MOLECULARanalysis

Clue?... This organic compound contains at leastone halogen.

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mass spec contd .MOLECULARanalysis

Clue: Molecule not featured earlier. Theempirical formula is C2H3O1

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mass spec contd .MOLECULARanalysis

Thats all folks !!!