Ring Strain and the Structure of Cycloalkanes

The molecular models made for Exercise 4-1 reveal obvious differences between cyclopropane, cyclobutane, cyclopentane, and so forth, and the corresponding straight-chain alkanes. One notable feature of the first two members in the series is how difficult it is to close the ring without breaking the plastic tubes used to represent bonds. This problem is called ring strain. The reason for it lies in the tetrahedral carbon model. The C-C-C bond angles in, for example, cyclopropane (60°) and cyclobutane (90°) differ considerably from the tetrahedral value of 109.5°. As the ring size increases, strain diminishes. Thus, cyclohexane can be assembled without distortion or strain. 

Does this observation tell us anything about the relative stability of the cycloalkanes—for example, as measured by their heats of combustion, AH° h How does strain affect structure and function This section and Section 4-3 address these questions. 

The heats of combustion of the cycloalkanes reveal the presence of ring strain 

Section 3-11 introduced one measure of the stability of a molecule its heat content. We also learned that the heat content of an alkane can be estimated by measuring its heat of combustion, (Table 3-7). To find out whether there is something special about the 

The A comb of a Strain-Free Cycloalkane Should Be Multiples of A ° n)b(CH2) 

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