While substituents tend to decrease the ring strain of the monomer, increasing the ring strain is also possible. The adduct that is formed when furan reacts with ethylene (r76) has a strain of 18.8 kcal/mol, the addition of two methyl groups (r78) decreases the strain to 16.2 kcal/mol, and this decrease can be compensated by the ethylene swapped for a benzyne. The use of a benzyne increases the ring strain dramatically, the non-substituted derivative (r73) has a strain of 27.9