Spin System Notation
Capital letters A, B, C, M, A, X, Y, …….
Same letter = same chemical shift (A3, B2, X6, ….)
Different letters = different chemical shifts
Letters close in the alphabet (A, B, C, …)
J [Hz] of the same magnitude as ∆ν [Hz]
Letters separated in the alphabet (A, M, X,…)
large separation of chemical shifts
-different nuclei (1
H, 31
P, 195
Pt,…)
-same nuclei but ∆ν [Hz] much larger than J
!! ∆ν [Hz] depends on B0 !!
Two situations:
a) Complete equivalence =
chemical shift equivalence (isochronous nuclei)
+ magnetic (spin-coupling) equivalence (isotachous)
Magnetic equivalence = each member of one group of spins is
coupled equally to all members of any other group
A2B2, A2X2,….
b) Chemical shift equivalence, magnetic inequivalence
AA’BB’, AA’XX’, AA’A’’XX’X’’, ….
Prime vs. Bracket Notation
AA’BB’ [AB]2
A2B2 [A2B2]
AA’BXX’ [AX]2B
AA’X3X3’ [AX3]2
AA’A”XX’X”X’’’X4
X5
[A[X]2]3
BB’AA’CC’A’’A’’’B’’B’’ [[AB]2C]2
considering isotope
shift:
ABB’CC’DX
A[BC]2DX
P
N
P
N
P
N
F F
F
F F
F
31P & 19F NMR
C
H
H
HH
H
H
13C NMR
H H
H
H
H H
H
H
H
H
1H NMR