Selective Enclathration of Picolines

Abstract

The host 1,1,2,2-tetraphenyl-1,2-ethane diol has been employed to separate the isomers 2-picoline (2-pic), 3-picoline (3-pic), and 4-picoline (4-pic) by selective enclathration. The crystal structures are all stabilized by (host)-O−H···N(guest) hydrogen bonds. The competition experiments show that enclathration preferentially takes place in the order 4-pic > 3-pic > 2-pic. The effect of benzene and methanol as “neutral” solvents shows that the former is incorporated as a guest in the 4-pic structure, thus enhancing the enclathration of 4-pic over 3-pic. Methanol displays no such effect.