Static dielectric constant, infra-red spectrum, and n.m.r. spectrum of straight-chain heptanols

Abstract

Static dielectric constants of the four straight-chain heptanols were determined in the temperature range from –70°C (or from the melting point) up to 100°C. For heptanol-4, the Kirkwood correlation factor g, computed from the static dielectric constant, reached a limiting value of about g= 1 at 60° C. According to the theory of Cole and Brot, one would conclude form this observation that above 60° C, heptanol-4 is no longer associated. The infra-red and n.m.r. spectra of pure heptanol-4 at different temperatures, however, indicate that heptanol-4 is still appreciably associated at temperatures far above 60°C. Therefore, it is concluded that Cole and Brot's theory concerning the dielectric constant of the mono-alcohols cannot be valid. Instead, one has to assume that in the pure liquid an important proportion of the molecules is associated as dimers, which have a low dipole moment.