LEC EIGHT THE CHEMICAL SHIFT PART IV USING

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LEC EIGHT THE CHEMICAL SHIFT PART IV USING
INTERPRETING COUPLING CONSTANTS PART I
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DONT FORGET DIAGNOSTIC Me SHIFTS (pp 78-81)
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DONT FORGET DIAGNOSTIC Me SHIFTS (pp 78-81)
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UNSATURATED MOLECULES

• Fungus Pyrenophra teres morphogenic substance A
  C10H10O4
• 13C/ 1H NMR Data from 1980 (no 2D NMR possible
  then!)

192.8 S 166.5 S 145.7 D 134.5 D 133.4 D 128.6 D
66.1 D 60.8 D 54.6 D 16.3 Q
6.75 1H D 17, 6 6.62 1H D 12 6.12 1H DD
17, 1.0 6.08 1H D 12 5.55 1H DQ 2, 7 3.78
1H DDD 6, 4.5, 1.0 3.20 1H DD 4.5, 2.0 1.5
3H D 7
3. Lets deduce a correct structure! 4. What
first?
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UNSATURATED MOLECULES

• Fungus Pyrenophra teres morphogenic substance A
  C10H10O4
• 13C/ 1H NMR Data from 1980 (no 2D NMR possible
  then!)

192.8 S 166.5 S 145.7 D 134.5 D 133.4 D 128.6
D 66.1 D 60.8 D 54.6 D 16.3 Q
195 164 147 143 124 127 67 63 57 16
6.75 1H D 17, 6 6.62 1H D 12 6.12 1H DD
17, 1.0 6.08 1H D 12 5.55 1H DQ 2, 7 3.78
1H DDD 6, 4.5, 1.0 3.20 1H DD 4.5, 2.0 1.5
3H D 7
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UNSATURATED GROUPS
PROTON SHIFTS ?4.3-6.4 CHART 3.1c (p82), 3.1e
(p86)
6.9
5.8
8.5
N
5.9 5.75 7.27
5.0
5.59
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SELECTED TRENDS
gt4.0
3.5
5.82 4.27
6.0 7.0
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UNSATURATED GROUPS
CARBON SHIFTS ?100 - 150 (CHART 3.1d (p84), 3.1f
(p89)
106
126
150
128.5
138.7
126, 124
125.6 149.5
197
162
129.8 150.6
106 152
144 99
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PROBLEM SOLVING
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SP C H (ALKYNE ALLENE)
1H RC?C-H 2-3 SPECIAL SHIELDING
MECHANISM RCCCHR 4.5 VINYL LIKE SHIELDING
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SP C H (ALKYNE ALLENE)
13C RC?C-H 70-90 SPECIAL ?para SHIELDING
RCCCHR gt200//70 ?para VINYL LIKE SHIELDING
FINAL CONSIDERATION UNUSUAL SHIELDING AT C?
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CO
1H R-CO(H) 9.4-10.5 13C R-CO(H/C)
195/gt200 ALDEHYDE 203 KETONE 205 AMIDE
175 ESTER 175 CARBOXYLIC ACID 180 O-C(O)-O
160 O-C(O)-N 150-160 N-C(N)-N 160
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CZ
NOTE ODD NUMBER OF SP2 CS 1H NONE 13C -C?N
110 -N?C 150-160 CUMULENES CNO
121 CNS 120-130 OTHERS CS 225
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USING INTERPRETING COUPLING CONSTANTS PART I
vs
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J THE MOST IMPORTANT NMR PARAMATER

• J SUPPORTS ESTABLISHING
• CHN-CHM CHAINS
• C HYBRID TYPE
• Z ATOMS AT C
• RING SIZE
• SYMMTERY
• DYNAMIC PROCESSES

I ½ I 0 I gt ½
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CONDITIONS FOR J-COUPLING
FOUR CASES

• N1 RULE APPLIES FIRST ORDER
• SUCCESSIVE APPLICATION OF N1 RULE
  COMPLEX 1ST ORDER
• N1 RULE NO GOOD NON-1ST ORDER
• N1 RULE NO GOOD CHEM EQUIV / MAG NON-EQUIV

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UNDERSTANDING SPECTRA
NH RESONANCES EXPLAINED
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UNDERSTANDING SPECTRA
NH RESONANCES EXPLAINED
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UNDERSTANDING SPECTRA
P104
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C8H802 UN 5
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SUMMARY

• Aliphatic Chemical alpha values useful in
  functional group ID.
• 2. C?C-R unusual upfield shift very diagnostic
  for this functionality.
• 3. Unsaturated Z 1H shift values useful for CC
  geometry assignement. Computer calc values also
  good!
• 4. Increment values are useful for 13C shift
  prediction of vinylic aromatic carbons.
• 5. J-coupling analysis is important 4
  situations.
• 6. N1 rule is often violated More examples
  to come.