MASS SPECTROSCOPY

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MASS SPECTROSCOPY
R W Grime Ripon Grammar School
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(No Transcript)
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• HIGH RESOLUTION MASS SPECTROSCOPY

• Molecular ion formed M ? M. e
• m/z value for M. gives the Mr.
• High resolution measures m/z to enough accuracy
  to find the molecular formula.

e.g. Mr 60 CH3COOH 60.02112 molecular formula
C2H4O2 NH2CONH2 60.03235 molecular formula
CH4N2O CH3CH2CH2OH 60.05751 molecular formula
C3H8O CH3CH(OH)CH3 60.05751 molecular formula
C3H8O
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• FRAGMENTATION

• Molecular ion fragments due to covalent bonds
  breaking M. ? X Y.
• Much information from fragmentation patterns
  can often work out structure.
• Relatively stable ions such as carbocations R
  and acylium ions R-CO are common.
• The more stable the ion, the greater the peak
  intensity.

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butane CH3CH2CH2CH3
C4H10 ? C4H10. e m/z 58
C4H10. ? CH3CH2CH2 .CH3
m/z 43
C4H10. ? CH3CH2 .CH2CH3 m/z 29
CH3CH2CH2
CH3CH2
C4H10.
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• ISOTOPES

• Ions with different isotopes produce different
  signals.
• Most important for Br and Cl.

Br 50 79Br 50 81Br Cl 75 35Cl
25 37Cl

• If two or more Br/Cl atoms, then spectrum is more
  complicated.
• Often small peaks at m/z 1 due to 2H and 13C.

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bromomethane CH3Br
CH381Br ? CH381Br. e m/z 96
CH379Br ? CH379Br. e m/z 94
CH3Br. ? CH3 .Br m/z 15
CH381Br.
CH379Br.
CH3
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chloroethane CH3CH2Cl
CH3CH237Cl ? CH3CH237Cl. e
m/z 66
CH3CH235Cl ? CH3CH235Cl. e
m/z 64
CH3CH237Cl. ? CH237Cl .CH3
m/z 51
CH3CH2
CH3CH235Cl. ? CH235Cl .CH3
m/z 49
CH3CH235Cl.
CH3CH2Cl. ? CH3CH2 .Cl
m/z 29
CH237Cl
CH235Cl
CH3CH237Cl.
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dichloromethane CH2Cl2
37Cl 35Cl 1 3
37Cl2 35Cl37Cl 35Cl2 1 6 9
CH235Cl
CH235Cl2.
CH237Cl35Cl.
CH237Cl
CH237Cl2.
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dibromomethane CH2Br2
81Br 79Br 1 1
81Br2 81Cl79Br 79Br2 1 2 1
174 CH281Br79Br.
95 CH281Br
93 CH279Br
172 CH279Br2.
176 CH281Br2.
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butanone CH3CH2COCH3
CH3CH2COCH3 ? CH3CH2COCH3. e
m/z 72
CH3CH2COCH3. ? CH3CH2CO .CH3
m/z 57
CH3CH2COCH3. ? CH3CO .CH2CH3
m/z 43
CH3CO
CH3CH2COCH3. ? CH3CH2 .COCH3
m/z 29
CH3CH2
COCH2CH3
CH3COCH2CH3.
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CH3CH2CH2COOCH3 ? CH3CH2CH2COOCH3. e
m/z 102
methyl butanoate CH3CH2CH2COOCH3
CH3CH2CH2COOCH3. ? CH3CH2CH2COO .CH3
m/z 87
CH3CH2CH2COOCH3. ? CH3CH2CH2CO .OCH3
m/z 71
CH3CH2CH2COOCH3. ? COOCH3 .CH2CH2CH3
m/z 59
CH3CH2CH2
CH3CH2CH2COOCH3. ? CH3CH2CH2 .COOCH3
m/z 43
CH3CH2CH2COOCH3. ? CH3CH2 .CH2COOCH3
m/z 29
CH3CH2CH2CO
COOCH3.
CH3CH2CH2COO
CH3CH2
CH3CH2CH2COOCH3.
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propyl methanoate
methylethyl methanoate
ethyl ethanoate
methyl propanoate
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propyl methanoate
m/z 59
OCH2CH2CH3
m/z 29
HCO
m/z 43
CH2CH2CH3
m/z 45
HCOO
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methylethyl methanoate
m/z 59
OCH2(CH3)2
m/z 29
HCO
m/z 43
CH2(CH3)2
m/z 45
HCOO
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ethyl ethanoate
m/z 45
OCH2CH3
m/z 43
CH3CO
m/z 29
CH2CH3
m/z 59
CH3COO
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methyl propanoate
m/z 31
OCH3
m/z 57
CH3CH2CO
m/z 29
CH2CH3
m/z 59
CH3OCO