Parameters with steep slope due to lack of diverse training data tend to produce unphysical k values when extrapolated below 1.
An edge case of t72 being replaced by an interpolated parameter TIG8 that has a steep slope.
t72 smarts: "[#8X1:1]~[#7X3:2]~[#6X3:3]~[*:4]"
t72: k = 0.74 kcal/mol
TIG8: k1_bo1 = 1.71, k1_bo2 = 10.5 kcal/mol
In the new amide dataset created by Simon Boothroyd, molecules that match t72 have a WBO spanning the range of 0.7 to 0.9
Few molecules with a lower WBO shown below
ELF10 WBO | Chemical structure | |
|---|---|---|
0.75 |  | |
0.75 |  | |
0.79 |  | |
0.72 |  |