N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
96
4 13 C NMR
Estimation of 13 C Chemical Shifts of Alicyclic Compounds (δ in ppm)
The 13 C chemical shift of the parent compound (e.g., 22.9 for cyclobutane, 26.0
for cyclopentane, and 27.1 ppm for cyclohexane) and the same increments as for
alkanes (see Chapter 4.1) can be used to estimate the chemical shifts of sp 3 -hybridized carbon atoms of alicyclic compounds. Appropriate use of the conformational
correction terms, K, is especially important with axial and equatorial substituents in
cyclohexanes. The additivity rule is, however, not suitable for estimating chemical
shifts of substituted cyclopropanes.
13 C Chemical Shifts of Unsaturated Alicyclics (δ in ppm)
108.7
124.5
26.0
28.7
124.9
28.8
134.1
130.9
129.8
128.2
123.3
134.3
152.6
123.4
132.8
131.5
2.3
23.0
29.8
29.5
27.1
28.8
cis
trans
cis, cis
22.3
23.3
41.6
137.2
31.4
127.4
25.4
128.5
28.5
126.1
124.6
130.8
32.8
130.4
26.0
27.0
130.2
25.7
26.4
132.7
132.7
34.3
34.4