Computing accurate bond dissociation energies of emerging per- and polyfluoroalkyl substances: Achieving chemical accuracy using connectivity-based hierarchy schemes

08 February 2024, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Understanding the bond dissociation energies (BDEs) of per- and polyfluoroalkyl substances (PFAS) bonds helps in devising their efficient degradation pathways. However, there is only limited experimental data on the PFAS BDEs, and there are uncertainties associated with the BDEs computed using density functional theory. Although quantum chemical methods like the G4 composite method can provide highly accurate BDEs (< 1 kcal mol-1), they are limited to small system sizes. To address DFT's accuracy limitations and G4's system size constraints, we examined the connectivity-based hierarchy (CBH) scheme and found that it can provide BDEs that are reasonably close to the G4 accuracy while retaining the computational efficiency of DFT. To further improve the accuracy, we modified the CBH scheme and demonstrated that BDEs calculated using it have a mean-absolute deviation of 0.7 kcal mol-1 from G4 BDEs. To validate the reliability of this new scheme, we computed the ground state free energies of seven PFAS compounds and BDEs for 44 C–C and C–F bonds at the G4 level of theory. Our results suggest that the modified CBH scheme can accurately compute the BDEs of both small and large PFAS at near G4 level accuracy, offering promise for more effective PFAS degradation strategies.


Connectivity-based hierarchy methods
Bond dissociation energies

Supplementary materials

Supplementary information
PFAS molecules and their numbering scheme, Fragment generating procedure for computing GSFEs, Computational time taken to obtain GSFEs using various levels of theory, The absolute deviation in the gas-phase BDEs of C1–O and O–H bonds of PFBA, The fragment generation procedure for computing the BDEs of various PFPeA bonds


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