The addition of methyl substituents to the 1 and 4 positions of the norbornene and oxanorbornene derivatives universally leads to a decrease in ring strain, however the effects of a lone substituent are mixed, in most derivatives there is at least a slight decrease (1-2 kcal/mol) of ring strain with the addition of a group at the one position, however the addition of another group at the 4 position drops the ring strain a total of 3-5 kcal/mol. Notably the RSE of the furan and cyclohexyl maleimide cycloadduct decreases by 5 kcal/mol with addition of methyl groups on the 1 and 4 position. A similar observation was made for the norbornene derivatives where Me groups on the 1,4 positions also decrease the ring strain by 5 kcal/mol. When the substituent added to the 1 and 4 positions is changed, there is a difference in how the RSE is affected. The furan and cyclohexyl maleimide cycloadduct shows an increase of 1 kcal/mol in RSE when one trifluoromethyl group is added, however when the molecule is disubstituted the ring strain drops down to 1.5 kcal/mol less than the non-substituted. This affect changes when it is modeled for the norbornene adduct which instead has a drop of 1 kcal/mol for one trifluoromethyl group and a drop totaling 4.5 kcal/mol less for the doubly substituted molecule than the non-substituted. The difference in the influence of the trifluoromethyl group on these two monomer sets could be due to the presence of lone pairs on oxygen, which allow for more polarization by the fluorine atoms, and could cause a more ridged cycle.