Figure 2:

The PMF profiles along the O=C-O-H torsion angle of acetic acid in the aqueous and gas phases, created through umbrella sampling with 61 windows for the real state (λ=0, the acetic acid has full interactions with the environment) and the dummy state (λ = 1, the acetic acid is fully decoupled from the environment) and with three gti_add_sc switches (see Table 1). In the gas phase, the preferred orientation is syn whereas in the aqueous phase, the preferred orientation is anti.