3 Combination Tables
3.1 Alkanes, Cycloalkanes
Assignment Range
Comments
CH 3
CH 2
CH
C
5–35 ppm
5–45 ppm
25–60 ppm
30–60 ppm
CH 3 , CH 2 , CH, and C can be differentiated
by multipulse experiments (DEPT, APT),
off-resonance decoupling, 2D CH correlation spectra, or based on relaxation times
Lower shift values in three-membered rings
CH 3
CH 2
CH
0.8–1.2 ppm
1.1–1.8 ppm
1.1–1.8 ppm
Lower shift values in three-membered rings
CH st
3000–2840 cm -1 Higher frequency in three-membered rings
CH 3 δ as
≈1460 cm -1
CH 2 δ
≈1460 cm -1
CH 3 δ sy
≈1380 cm -1 Doublet for geminal methyl groups
CH 2 γ
770–720 cm -1 In C–(CH 2 ) n –C with n ≥ 4 at ≈720 cm -1
Molecular ion m/z 14n + 2
Weak in n-alkanes
Very weak in isoalkanes
Fragments
n-Alkanes: local maxima at 14n + 1, intensity
variations: smooth, minimum at [M-15] +
Isoalkanes: local maxima at 14n + 1, intensity
distribution: irregular (relative maxima due
to fragmentation at branching points with
charge retention at the most highly substituted C)
Rearrangements
m/z 14n
m/z 14n - 2
n-Alkanes: unspecific
Isoalkanes: elimination of alkanes
Monocycloalkanes: elimination of alkanes
No absorption above 200 nm
13 C
1 H
IR
MS
UV
© The Author(s), under exclusive license to Springer-Verlag GmbH, DE,
part of Springer Nature 2020
E. Pretsch et al., Structure Determination of Organic Compounds,
https://doi.org/10.1007/978-3-662-62439-5_3
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