Early Events in the Reductive Dehalogenation of Linear Perfluoroalkyl Substances

This work details
the early events in the reductive defluorination
of perfluoroalkyl substances (PFASs) and presents a straightforward
methodology for predicting the reduction behavior of the perfluoroalkyl
acids (PFAAs) using electronic structure calculations. Electron attachment
to linear perfluorocarboxylic acids generally occurs at the α-carbon
and is energetically not correlated to chain length, contrary to the
case for linear perfluoroalkanesulfonates, where electrons generally
insert into other positions. Perfluorooctanesulfonate and perfluorooctanoic
acid, two widely studied and scrutinized PFAAs, are therefore predicted
to be reduced through diverging pathways. Our protocol can predict
the standard reduction potentials of PFAAs, provides a rational basis
for probing reaction intermediates, establishes free energy relationships,
and accounts for PFASs’ inherent structural diversity beyond
the linear substrates.