LEC SEVEN THE CHEMICAL SHIFT PART III PROTON

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LEC SEVEN THE CHEMICAL SHIFT PART III PROTON
CARBON
HOW MANY DISTINCT METHYL SIGNALS? 3_____ 4______
5______ 6 ________
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CHEMICAL SHIFT EQUIVALENCE 13C 1H ISOPROP VS.
TERT-BUTYL
HOW MANY Me 13C 1H RESONANCES AT ROOM TEMP?
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1
1
3
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SYMMETRY EFFECTS ASSIGN RESONANCES
Q
D
Q
T
S
Q
1 6 3 2 6
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ASSIGN RESONANCES
2
4 5
3
1
6
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CHARACTERISTIC ?s1H 13C
MODEL COMPOUNDS CHARTS 3.1a 3.1i CALCULATED
SHIFTS TABLES 3.5- 3.11 SOFTWARE or WEBsites
What is your favorite?

• ALIPHATIC PROTONS
• 0.2 7.5 (CHART 3.1a) P68
• BUT 2-METHYL PENTANE ? 0.8 1.5

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FIRST ORDER
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SHOOLERYS RULES
P73
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USING SHOOLERYS RULES
C4 ?exp 2.01 ?calc X CCH- Z
CH2R 1.40 0.88 2.28 C3
?exp 1.6 ?calc 0.88 0.88
1.76
O
3
4
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TWO DIFFERENT STRUCTURES BUT, SAME NMR DATA!
pyrostatin B C6H10N2O2 J. Enzyme Inhibition 1995,
8, 223.
ectoine C6H10N2O2 Eur. J. Biochem. 1993, 214, 897.
177.0 (C)/ 161.5 (C)/ 53.6 (CH), 4.06 dd, J5.4,
5.4 / 38.0 (CH2), 3.28 ddd, J13.5, 8.4, 4.8/
23.6 (CH2), 2.11 m/ 19.1 (CH3), 2.22 s
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TWO DIFFERENT STRUCTURES BUT, SAME NMR DATA!
pyrostatin B C6H10N2O2 J. Enzyme Inhibition 1995,
8, 223.
ectoine C6H10N2O2 Eur. J. Biochem. 1993, 214, 897.
177.0 (C)/ 161.5 (C)/ 53.6 (CH), 4.06 dd, J5.4,
5.4 / 38.0 (CH2), 3.28 ddd, J13.5, 8.4, 4.8/
23.6 (CH2), 2.11 m/ 19.1 (CH3), 2.22 s
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ALIPHATICS CARBON SHIFTS GENERAL (SP3)
?10 100 UNFUNCTIONALIZED
?10 - 50 (CHART 3.1b)
21.9
31.7
29.7
11.4
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ALIPHATICS CARBON SHIFTS GENERAL (SP3)
?10 100 UNFUNCTIONALIZED
?10 - 50 (CHART 3.1b)
21.9

• SHIFTS ARE ADDITIVE
• ?para DOMINANT
• NON-LINEAR EFFECTS

31.7
29.7
11.4
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ADDITIVE PATTERNS
P76
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UNDERSTANDING TABLE 3.6
?
?
4
2
1
3
?
?
31

• 20 para
• 10 para
• -2 to -3 diam
• ? 0

3?
also
61
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P77
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TWO DIFFERENT STRUCTURES BUT, SAME NMR DATA!
pyrostatin B C6H10N2O2 J. Enzyme Inhibition 1995,
8, 223.
ectoine C6H10N2O2 Eur. J. Biochem. 1993, 214, 897.
177.0 (C)/ 161.5 (C)/ 53.6 (CH), 4.06 dd, J5.4,
5.4 / 38.0 (CH2), 3.28 ddd, J13.5, 8.4, 4.8/
23.6 (CH2), 2.11 m/ 19.1 (CH3), 2.22 s
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SUMMARY

• Chemical shift assignments require analysis of ?
  symmetry.
• 2. An (CH3)2CH- is a good reporter group, but a
  (CH3)3C- is a symmetrical top.
• 3. Shoolerys Rules (H) shifts somewhat useful
  for 1H shift prediction of XCH2-Y.
• 4. Table 3.6 increment values are useful for 13C
  shift prediction of aliphatics.
• 5. Commercial software is a best way to analyze
  both 1H and 13C shift trends.
• 6. Some important terms Concise approach
  tactic used in successfully solving in class Quiz
  Problems!