Abstract Conductometric measurements on solid rubidium and cesium propanoates and X-ray powder diffraction measurements on the rubidium salt have been carried out over suitable temperature ranges. The results obtained, along with the previous ones concerning the lithium, sodium and potassium salts, have been discussed in relation to possible melting mechanisms (involving various kinds of disorder, e.g., positional, orientational, conformational) active in the alkali alkanoates family.