Studies in coal tar bases. I. Separation of β‐ and γ picolines and 2:6‐lutidine

Abstract

Abstract Tar base fractions commonly described as “commercial β‐picoline” are mixtures containing β‐ and γ‐picoline and 2 : 6‐lutidine in variable, if usually roughly equal proportions. Many methods for the separation of one or more of the individual components have been proposed yet few are suitable for commercial exploitation. In the present paper it is shown that by azeotropic fractional distillation the three bases may be readily separated in purities of 95‐98% and with little loss, if acetic or propionic acids are used as azeotropic‐formers, and it is possible to recover for re‐use the acids from the separate base‐acid azeotropes with the aid of a suitable hydrocarbon entrainer. It is also shown that the hydrochlorides of the bases differ very markedly in physical properties and can be easily separated. Pure specimens of the three bases were obtained by fractional freezing of 95‐88% pure materials : 2 : 6‐lutidine, b.p. 144°, f.p. −5·97°; β‐picoline b.p. 1447middot;0°, f.p. −177middot;77°; γ‐picoline b.p. 145·37°, f.p. + 47middot;3°.