 Nonbonded 1,3-diaxial interaction energies are commonly used to approximate strain energy in cyclic molecules, as values for these interactions are available.By taking the difference in nonbonded interactions for each conformer, the equilibrium enthalpy can be estimated.The strain energy for methylidenecyclohexane has been calculated to be 4.5 kcalmol−1 using estimations for 1,3-diaxial strain (0.9 kcalmol−1), methyl/hydrogen allylic strain (1.3kcalmol−1), and methyl/methyl allylic strain (7.6 kcalmol−1) values.