The melting points, solubility, and relative stability of the 2·4 dichloranilides of the normal fatty acids

Abstract

In an homologous series there exists, between the members, a definite relationship in their chemical and physical properties. In general the densities approach a constant value as the series is ascended, while the melting and boiling points continue to rise though the successive differences become smaller and smaller. There are however, exceptions to this general rule. Von Baeyer first showed that the melting points of the normal fatty acids show alternate rise and fall with the addition of each successive carbon atom in the chain, and that a regular series of figures can be obtained only by considering the odd and even members separately. A study of the normal fatty acids showed that with successive additions of CH₂ groups the melting points first fall to a minima then gradually rise. Also that on plotting melting point against number of carbon atoms in the chain of the acid, the odd and even members of the series fall on two distinct curves. Similar effects are produced by the anilides of the fatty acids. Both are shown in Fig.1.