We used the energy difference cis-2-butene and trans-2-
butene twisted to a CCCC dihedral angle that matches
those found in the trans cycloalkenes as the energetic cost of
the double bond in the trans cycloalkenes, ΔE(cis-twist trans) 2-
butene. The calculated OSE and the contributions of the double
bond to the strain energy in the trans cycloalkenes are listed
in Table 4. From trans-cyclohexene through trans-cyclononene
the majority of the strain energy is caused by twisting about
the CC double bond. The approximated strain caused by
the twisted CC double bond in the trans isomers of
cyclohexene through cyclononene ranges from 64–87% of
the total strain energy. There is minimal calculated twisting
and pyramidalization in trans-cyclodecene; likewise, the calculations
show a small contribution from the CC double
bond to its total OSE. It is noteworthy that medium-sized
cycloalkenes place most of the strain energy in distortions to
the CC double bond, as opposed to other possible locations.