LECTURE 17 FRAGMENTATION MECHANISMS

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LECTURE 17FRAGMENTATION MECHANISMS
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EI - INDUCED FRAGMENTATION
WHERE IS THE ODD e- LOCALIZED? R-R
R-R.
3
p244
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PROBLEM SOLVING
M
FRAGMENT IONS
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PROBLEM SOLVING
M
FRAGMENT IONS
1. Br 2. 73 C5H13 (R-135/8) 3. MS Calc
C6H13OBr
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PROBLEM SOLVING
M
FRAGMENT IONS

• Br 2. 73 C4H9O (OR,-CH4) 3. MS Calc
  C6H13OBr
• 
  C5H9O2Br

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THREE TYPES OF FRAGMENTATIONS

• ? - CLEAVAGE AT ONE BOND
• ? - CLEAVAGE AT TWO BOND OR REARRANGEMENT
• COMPLEX REARRANGEMENTS

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P243
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ONE BOND ?-CLEAVAGE
P244
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ONE BOND ?-CLEAVAGE
MW 45
P248
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?-CLEAVAGE
P249
12
P243
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TWO BOND ?-CLEAVAGE
P250
14
P251
McLAFFERTY REARRANGEMENT
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NO SIMPLE RULE BOOK HERE!
P243
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ODD EVEN RULE IN FRAGMENTATION
P246
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ODD EVEN RULE IN FRAGMENTATION
REMEMBER EI ? M
odd soft ESI or CI ? MH
even
P246
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OTHER IMPORTANT RULES

• LOSS OF M/Z 14 NOT POSSIBLE
• M-CH2 OR F-CH2
• 2. ORDER OF R OR R LOSS 3gt2gt1gtMegtH
• LOSS OF LARGEST ALKYL CHAIN PREFERRED
• 3. FRAG ION STABILITYgtRADICAL FRAG STABILITY
• 4. LOSS OF NOT FAVORED

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USING ALKANES TO REVISIT FRAGMENTATION MECHANISMS
P253
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USING ALKANES TO REVISIT FRAGMENTATION MECHANISMS
Ref 1 (pp52-54)
P253
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USING ALKANES TO REVISIT FRAGMENTATION MECHANISMS
43 / 57 / 71 / 85 / 99 C3H7/ C4H9/ C5H11/ C6H13/
C7H15/
P253
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too big 71 127
85 99 113 127
43 / 57 / 71 / 85 / 99 /113 / 127 C3H7/ C4H9/
C5H11/ C6H13/ C7H15/ C8H17 / C9H19
P253
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43 / 57 / 71 / 85 / 99 C3H7/ C4H9/ C5H11/ C6H13/
C7H15/
P247
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43 / 57 / 71 / 85 / 99 /113 / 127 C3H7/ C4H9/
C5H11/ C6H13/ C7H15/ C8H17 / C9H19
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(No Transcript)
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PROBLEM SOLVING
M
FRAGMENT IONS
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THE MS PLUS NMR DATA
M180?M-H179 ?MS 180 79
101 C5H9O2 C6H13O1
C7H17 NMR 2(CH2)2(CH2)CH C5H9
O2-3 C5H9BrO2 180
C5H9BrO3 196
D T T T
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THE MS PLUS NMR DATA
M180?M- H179 ?MS 180 79
101 C5H9O2 C6H13O1
C7H17 NMR 2(CH2)2(CH2)CH C5H9 O2-3
C5H9BrO2 180
C5H9BrO3 196
D T T T
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THE MS PLUS NMR DATA
M180?M- H179 ?MS 180 79
101 C5H9BrO2 C6H13O1
C7H17 NMR 2(CH2)2(CH2)CH C5H9 O2-3
C5H9BrO2 180
C5H9BrO3 196
UN 1
D T T T
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WORKING STRUCTURES
FOUR CARBON TYPES D T/T T T
Ds 2 1
1 2
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WORKING STRUCTURES
FOUR CARBON TYPES D T/T T T
Ds 2 1
1 2
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WORKING STRUCTURES A DECISION
C2H4Br 107
M-28 -C2H4
M-43 -C3H7
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WORKING STRUCTURES
FOUR CARBON TYPES
C2H4Br 107/109 C3H5O2 73
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SUMMARY

• EI fragmentation EI ? M consider where e- is
  localized.
• EI fragmentation EI ? M consider three
  mechanisms
  (a) one bond ?-clevage,
  (b) two one bond ?-clevage (RDA)
  (c) complexMcClafferty (featured in Chem
  112)
• EI fragmentation EI ? M consider four
  important rules HTL no loss of 14 by CH2.
• MS-calculator or Frag-calculator (MS calc
  pro) needed to interpret the data.
• EI-MS fragments NMR great combo for problem
  solving.