Diffraction studies of molecular interaction. Low electron-density fluctuations induced by association

The scattering which arises from the difference in electron density between the environment around an internal atom of a molecule in a condensed phase and one at a terminal position has been measured. The examples offered here are C atoms positioned in a chain and at the end. The results are discussed in terms of association, where an in-register association is favored, because in this configuration attraction of the chain subunits is maximized. Consequently, the electron-deficient chain ends also tend, on the average, to be in register. It is found that the association persists even when a diluent is added to the system. The technique is not restricted to chain-like molecules, and can in principle be used to measure the association and dimensions of other large organic molecules.