Cycloalkanes and Saturated Heterocyclics

The chemical shifts of the CH2 groups in monocyclic alkanes are given in Table 5.4. 

The striking feature here is the strong shift to the right of cyclopropane, analogous to the shift of its proton absorptions. 

Each ring skeleton has its own set of shift parameters, but a detailed listing of these is beyond the scope of this text. Rough estimates for substituted rings can be made with the substitution increments in Table 5.3. 

One of the striking effects in rigid cyclohexane rings is the shift to the right caused by the y-gauche steric compression. Thus an axial methyl group at C-l causes a shift to the right of several parts per million at C-3 and C-5. 

The sp2 carbon atoms of alkenes substituted only by alkyl groups absorb in the range of about 110-150 ppm. 

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