Transcript Introductory NMR 101 - University of Minnesota

 Chemical Shift
Introductory NMR 101
 Chemical Shift
 Peak Intensity
 Spin-spin Coupling
 Sample Preparation: Deuterated Solvents
 Spin-spin Coupling
Karplus (Garbisch) Relationships: Correlation of Magnitude of J Value w/ Geometry
147
6.5
12
6
10
5.5
J (Hz)
5
8
4.5
64
3.5
4
3
2
2.5
02
0
45
90
angle
135
180
 Spin-spin Coupling
Protocola-c for Computational/NMR Strategy
1.
Determine as many experimental coupling constants Jexp( 3J and 4J)
as possible.
2.
Subject each diastereomer to multiconformational search (e.g., Monte
Carlo in MacroModel) to identify the family of stable conformational
isomers and then compute the Boltzmann weighted coupling constants
Jcalc for each diastereomer.
3.
Calculate 2’ between the experimental Js and the computed Js. The
isomer with smallest 2’ (best fit) is the proposed structure.
2’ = ∑(Jexp-Jcalc)2
 Spin-spin Coupling
Extracting Coupling Constants from First Order Multiplets
4096
J. Org. Chem. 1994, 59, 4096-4103
A Practical Guide to First-Order Multiplet Analysis in
1H NMR Spectroscopy
Thomas R. Hoye,* Paul R. Hanson,1a and James R. Vyvyan1b
Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
Received March 11, 1994
The ability to deduce the proper set of coupling constant (J) values from a complex first-order multiplet in a 1H
NMR spectrum is an extremely important asset. This is particularly valuable to the task of assigning relative
configurations among two or more stereocenters in a molecule. Most books and treatises that deal with
coupling constant analysis address the less useful operation of generating splitting trees to create the line
pattern from a given set of J values. Presented here are general and systematic protocols for the converse--i.e.,
for deducing the complete set of J values from the multiplet. Two analytical methods (A. systematic analysis
of line spacings and B. construction of what can be called inverted splitting trees) are presented first. A
reasonably thorough and systematic set of graphical representations of common doublet of doublets (dd's),
ddd's, and dddd's are then presented. These constitute a complementary method for identification of J's
through visual pattern recognition. These approaches are effective strategies for extraction of coupling
constant values from even the most complex first-order multiplets.
 Spin-spin Coupling
Table 7. dddd's Where Jz = J y and J x = J w (app tt's).
Jz = Jy
entry
a
Multiplet Appearance
1
b
2
3
1
2
c
1
d
3
2
1
e
2
1
4
5
6
4
5
6
3 4
5
6 7
3/4
5
6/7
7
J14 = J14'
7
8
8
9
8
8
2 4 3 5 7 6 8
9
9
9
9
f
1
2/4 3/5/7 6/8

Spe cial
J12 = J12' J's Re lations hips
Jx = Jw
8=8
2=2
20
6=6
2=2
16
5=5
2=2
14
4=4
2=2
12 J14 = J 12 + J12'
3=3
2=2
10
2=2
2=2
8
1=1
2=2
6 J12 = J 14 + J 14'
0=0
2=2
4
9
g
1 4 2/7 5 3/8 6 9
h
1/4/7 2/5/8 3/6/9
-10
-8
-6
-4
-2
0
2
J14 = J 12
4
6
8
10H z
 Spin-spin Coupling
Extracting Coupling Constants from NMR Multiplets: An Addendum
H
H
OH OH
H
OPMB
Me
H
Me
H
Me
Me
H
OH
OH
OPMB
H
"A Practical Guide to First-Order Multiplet Analysis in 1H NMR Spectroscopy,"
Hoye, T. R.; Hanson, P. R.; Vyvyan, J. R. J. Org. Chem. 1994, 59, 4096-4103.
"A Method for Easily Determining Coupling Constants. An Addendum to …"
Hoye, T. R.; Zhao, H. J. Org. Chem. 2002, 67, 4014-4016.
 Spin-spin Coupling
 Spin-spin Coupling
Two Steps to Identify all J’s in a Multiplet
1. Assign each peak in the multiplet one or more component numbers
from 1 to 2n (arbitrarily) from left to right by analogy to the examples shown below.
a) ddd
1 2 3 4
5 6 7 8
b) ddd
1
2
3
4
6
7
8
5
c) dddd
1
2
3
45
6
9 1213 14
7
10
8
11
15
16
 Spin-spin Coupling
2. Systematically identify the J's by the following series of steps. Adopt the
convention that J1 ≤ J2 ≤ J3 ≤ J4 ≤ … Jn. Appreciate that for J3 and beyond it is
necessary to have first determined the previous coupling constants (e.g., both J1
and J2 must be known before J3 can be determined). {1 to x} is the distance in Hz
between component 1 (i.e., the lefthandmost peak) and component x.
i)
{1 to 2} is J1
ii)
{1 to 3} is J2
iii)
remove from further consideration the component corresponding to (J1 + J2)
iv)
{1 to next higher remaining component (i.e., 4 or 5)} is J3
corollary: one of {1 to 4} or {1 to 5} is J3
v)
remove from further consideration the components corresponding to the remaining combinations
of the first three J values [i.e., (J1 + J3), (J2 + J3), and (J1 + J2 + J3)
vi)
{1 to the next higher remaining component} is J4
corollary: one of {1 to 5} through {1 to 9} is J4
 Spin-spin Coupling
Application to a dddd (24 = 16)
J2
J1
1
2
3
4 5
6
7
8
9
10
11
12 13
14
15
16
assign 2 n components (or "units of intensity")
 Spin-spin Coupling
Application to a dddd (24 = 16)
J3
J2
J1
J2
J1
1
2
3
4 5
6
7
8
9
10
11
12 13
14
15
16
assign 2 n components (or "units of intensity")
 Spin-spin Coupling
2. Systematically identify the J's by the following series of steps. Adopt the
convention that J1 ≤ J2 ≤ J3 ≤ J4 ≤ … Jn. Appreciate that for J3 and beyond it is
necessary to have first determined the previous coupling constants (e.g., both J1
and J2 must be known before J3 can be determined). {1 to x} is the distance in Hz
between component 1 (i.e., the lefthandmost peak) and component x.
i)
{1 to 2} is J1
ii)
{1 to 3} is J2
iii)
remove from further consideration the component corresponding to (J1 + J2)
iv)
{1 to next higher remaining component (i.e., 4 or 5)} is J3
corollary: one of {1 to 4} or {1 to 5} is J3
v)
remove from further consideration the components corresponding to the remaining combinations
of the first three J values [i.e., (J1 + J3), (J2 + J3), and (J1 + J2 + J3)
vi)
{1 to the next higher remaining component} is J4
corollary: one of {1 to 5} through {1 to 9} is J4
 Spin-spin Coupling
Application to a dddd (24 = 16)
vi)
J4
v)
J3
J2
v)
J3
J2
v)
J3
J1
iv)
J3
iii)
ii)
J2
J2
i)
J1
1
J1
J1
2
3
4 5
6
7
8
9
10
11
12 13
14
15
16
 Spin-spin Coupling
Assigning Component #’s is Harder for Some Multiplets (e.g., dddddd)
H
H
H
H
O
Ha
Me
H
O
Me H
Hb
O
PMB
 Spin-spin Coupling
Resolution Enhancement: Relative Line Intensity Now Easier
H
H
H
O
Ha
Me
H
O
6
3
3
2
1
J1 J2 J5
J3 J6
J4
J total = 43.7 Hz (observed: 44.0 Hz)
PMB
O
Me H
Hb
1
J = 4.1, 7.0, 7.0, 7.0, 9.3, and 9.3 Hz
H
5
8
3
dddddd
 Spin-spin Coupling
Splitting Tree: to Confirm the Assignments
H
H
H
H
O
Ha
Me
H
O
Me H
Hb
dddddd
O
PMB
 Spin-spin Coupling
Spiruchostatins A and B: A Challenging Opportunity to Test the Method
H D
N
O
Novel bicyclic depsipeptides
O
Isolated from Pseudomonas sp.
NH
S
H
Me
S
Me
D
OH
NH
Me
O
O
O
Spiruchostatin A
Mimics t ransf orming growt h f act or-
( TGF-) , which suppresses growt h of
various t umor cell lines
Ala and Cys configurations are D
"The establishment of the remaining
stereochemistries is now under way." 1
1. Masuoka, Y.; Nagai, A.; Shin-ya, K.; Furihata, K.; Nagai, K.; Suzuki, K.; Hayakawa, Y.;
Seto, H. "Spiruchostatins A and B, novel gene expression-enhancing substances produced by
Pseudomonas sp.," Tetrahedron Lett. 2001, 42, 41-44.
 Spin-spin Coupling
Strategies for Ferreting Out the Js
• To overcome peak broadening:
a) Variable temperature NMR
b) Resolution enhancement
• To overcome peak overlap:
a) Mixed solvents: benzene-d6 “titration”
b) Complementary field strengths
 Spin-spin Coupling
Variable Temperature NMR
H
O
H O
H
N
N
H
H
Me
N
H
i-Bu
S
S
H
OH
H
H
H
OH
H
H
2''
2'''
H
H
O
H
••
2''
O
H
6'''
2'''
4''
3'
••
•
3'
7'''
7'''
• •
O
OH
6''
60 °C
25 °C
3.5
3.3
3.1
2.9
2.7
2.5
2.3
 Spin-spin Coupling
Resolution Enhancement Gives Critical 3’’’-H (ddddd) Js
3'''-H
(ddddd 1.9, 1.9, 1.9, 3.8, 7.0)
O
H
N
O
NH
S
H
Et
S
For easy deconvolution of
J1
first order Js see:
J2
Hoye, T. R.; Zhao, H.
J3
J. Org. Chem. 2002,
J4
67, 4014-4016.
Me
Me
NH
OH
3'''
O
O
O
H
J5
60 °C
5.53
5.52
5.51
5.5
5.49
5.48
5.47
 Spin-spin Coupling
Resolution Enhancement (cont’d)
7'''-H
(ddd 2.9, 8.2, 11.4)
•
H
3'-H
(dd 3.9, 15.0)
O
•
N
H
3.154
3.134
3.114
3.094
3.074
3.054
5.63
5.62
5.61
5.6
i-Bu
S 7''' H
H
H
6''' H
4'''H
H
O
H
OH
H
H
O
6'''-H
(dddd 2.4, 9.6, 12.0, 15.0)
•
5.64
S
3.034
4'''-H
(ddd 2.1, 2.1, 15.4)
5.65
N
H
3' H
O
3.174
H
N
Me
H
H O
•
5.59
5.58
2.52
2.5
2.48
2.46
2.44
 Spin-spin Coupling
Overcome Peak Overlap by Mixed Solvent ( 17 % Benzene-d6 in CDCl3)
H
O
H O
H
N
N
H
H
Me
S
S 7''' H
N
H
OH
H
H
H
245
H
H
6''' H
O
OH
2'' a
•
H
O
H
•
O
145
2'' b
• • •
7'''
17 % C6D6
7''' (dddd
3.0, 3.0, 9.2, 13.1)
195
H
•
H
i-Pr
6''' (dddd
3.2, 5.5, 6.5, 13.1)
•
95
6'''
45
-5
60 °C
2.7
2.65
2.6
2.55
2.5
0 % C6D6
2.8
2.75
2.7
2.65
2.6
2.6
2.58
2.56
2.54
2.52
2.5