Further Studies on the Relation Between Constitution and Association: Especially in Reference to Aromatic Compounds

Abstract

The fluidities of fifteen ortho, meta and para compounds have been measured at temperatures of 0°C to 100°C, except when the melting point of the compounds interfered with measurements at the lower temperatures. The specific volumes of 14 of these compounds have been measured at the same temperatures. From the atomic temperature constants of C, H, O, Cl, Br and N given by Bingham and Spooner, the associations of the compounds have been calculated, whenever possible, at fluidities of 50, 100 and 200 rhes. From these same constants, and that of F determined by the authors, the associations of 14 ortho, meta and para compounds run by Swarts have been calculated at equal fluidities. On the basis of the theory of protection, the associations of these 29 compounds and of 17 ortho, meta and para compounds studied previously have been correlated. In the case of compounds containing two non-associating groups, (A) The fluidity-temperature curves of the meta and para compounds cross, the para compound having the higher temperature coefficient of fluidity. (B) At low temperatures, the ortho compound is the most associated, the para next, and the meta compound has the least association. (C) At high temperatures, the ortho compound is the most associated, the meta next, and the para has the least association. In the case of aromatic compounds, containing one non-associating and one associating group, the differences will be less clearly marked, but: (A) In general, the ortho compound is the least associated, the meta next, and the para compound is most associated. (B) In the phenetidines, at low temperatures, the meta compound is more associated than the para compound, but, having a higher temperature coefficient of fluidity, its fluidity-temperature curve shows a tendency to cross that of para-phenetidine, and at high temperatures, the associations will run o<m<p. (C) Where the associating group is NO2, the associations of the three isomers are nearly equal, with that of the meta compound being slightly lower than the associations of the ortho and para compounds. In the case of compounds containing two associating groups, according to the theory, the associations should run o<m<p. Time was not available to run any of these compounds, and there are no fluidity data on them in the literature since all are solids at ordinary temperatures. In general, however, the boiling points of these substances, which vary in the same order as the association, run o<m<p (Table V). Unfortunately, even these data are scanty. It is shown that the theory of protection offers an explanation for the behavior noted above.