using nmr spectra to identify unknowns
DESCRIPTION
Using NMR Spectra to Identify Unknowns. Identifying Unknowns. The Markovnicov product is the expected product Predict a proton NMR for the product:. What Product Was Formed?. Proton NMR not consistent Further analysis indicates C 5 H 9 ClO formed What is the structure?. - PowerPoint PPT PresentationTRANSCRIPT
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Using NMR Spectra to Identify Unknowns
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Identifying Unknowns
• The Markovnicov product is the expected product
• Predict a proton NMR for the product:
O HCl
Cl
O
expected
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012345PPM
1H
2H3H
3H
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What Product Was Formed?
• Proton NMR not consistent• Further analysis indicates C5H9ClO formed• What is the structure?
01234PPM
2H 2H
2H
3H
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Step 1: Make data table
01234PPM
2H 2H
2H
3H
Signal Shift (ppm) Integration Splitting
A 3.7 2 Triplet (n=2)
B 2.7 2 Triplet (n=2)
C 2.5 2 Quartet (n=3)
D 1.1 3 Triplet (n=2)
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Step 2: Pieces
• Based on integration, MF• Degrees of unsaturation
for C5H9ClO = 1
Signal Shift (ppm)
Integration Splitting
A 3.7 2 Triplet (n=2)
B 2.7 2 Triplet (n=2)
C 2.5 2 Quartet (n=3)
D 1.1 3 Triplet (n=2)
A = -CH2-B = -CH2-C = -CH2-D = -CH3
C
O
Cl
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Step 3: Link pieces together
• Use Splitting• Use shift
• Piece A must be connected to –Cl because of shift• Piece A must be connected to methylene because
of n=2
Signal Shift (ppm)
Integration Splitting
A 3.7 2 Triplet (n=2)
B 2.7 2 Triplet (n=2)
C 2.5 2 Quartet (n=3)
D 1.1 3 Triplet (n=2)
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Step 4: Test proposed structure
• Does proposed structure match data?O
Cl
Signal Shift (ppm)
Integration Splitting
A 3.7 2 Triplet (n=2)
B 2.7 2 Triplet (n=2)
C 2.5 2 Quartet (n=3)
D 1.1 3 Triplet (n=2)
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Problem 1: C5H10O2 ester
012345PPM
2H
3H
2H
3H
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Problem 2: C10H12O2
024681012PPM
s, 3
m, 15
t, 6
t, 6
qn, 6
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Problem 3: C10H14O ether
• What should you do with 7ppm and 7.3ppm?• Signal at 1.9ppm: hard to tell how many peaks
012345678PPM
2H
3H 2H
1H
6H
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Problem 4: C7H12Cl2
0123456PPM
s, 1H
q, 2H
s, 3H
s, 3H
t, 3H
020406080100120140PPM
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Problem 5: C10H14
012345678PPM
1H
1H
2H
4H
6H
020406080100120140PPM