mo|lec|u|lar so|ci|ol|o|gy, n (german: Molekularsoziologie ), the scientific study of molecular societies and molecular behaviour in groups, see Vierteljahrsschr.  Naturforsch. Gesellsch. Zürich 142 (1997) 133-143

Interactions between molecules may be compared to interactions between animals or human beings (although molecular behaviour tends to be much more reproducible), hence the allegorical term molecular sociology (see also J.-M. Lehn, Supramolecular Chemistry, VCH, 1995, p.2). Molecular sociology is at the heart of important research topics such as molecular biology and materials science, since it describes molecular recognition as well as molecular cohesion. Atmospherical processes such as cloud formation also involve molecular interactions. In a narrow sense, molecular sociology involves interactions which leave the molecular entities intact, although their properties may be affected. More vigorous processes such as chemical reactions are often preceeded by intermolecular interactions.

The hydrogen bond is among the most important molecular partnerships. Hydrides of electronegative elements, mainly from the first row of the periodic system, can act as hydrogen donors toward a molecule with a free electron pair (the acceptor). If both partners are equivalent, they can easily exchange their donor/acceptor roles. Quantum mechanical tunneling enables this exchange even at the zero point level. The resulting gain in energy from such an exchange is typically quite modest, since relatively large energy barriers have to be overcome on the way.

Experimental molecular sociology profits a lot from the ability to prepare isolated molecular pairs or larger molecular assemblies in well defined states. This can be done quite conveniently in supersonic expansions of gas mixtures, and the molecular behaviour can be monitored  comprehensively using Fourier transform infrared spectroscopy. The combination of both techniques is called jet-FTIR.