Accurate Thermodynamics of Phenol Aggregates across Concentration and Temperature

Phenol aggregate populations in carbon tetrachloride are governed by an enthalpy–entropy balance that varies with concentration and temperature. Changes in these thermodynamic conditions redistribute the population among aggregates, which is reflected in the infrared O–H stretching band, whose position and shape provide a sensitive test for population models. Here, monomer-to-tetramer populations are determined over a concentration–temperature grid using two strategies that share the same graph-based aggregate classification: a cluster-based approach relying on partition functions from conformational-search structures, and a trajectory-derived approach extracting populations from molecular dynamics simulations. The latter reproduces the experimental attenuation and displacement of the aggregate-associated bands, especially in concentrated solutions, whereas the cluster-based model predicts an overly sharp thermal depletion of larger aggregates. Temperature-dependent data further enable van’t Hoff estimates of aggregation enthalpies and entropies. Comparison with the experiment shows that the trajectory-derived strategy captures aggregation thermodynamics across the aggregate series, supporting a better sampling of the configurational space.