Studies of the Formation and Stability of Urea Inclusion Compounds

A study was undertaken to determine the relative ease of formation and stability of straight-chain primary and secondary alkanols capable of forming urea inclusion compounds. The compounds studied were 1-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-heptanol, 1-octanol, 3-octanol, 4-octanol, 1-nonanol, 4-nonanol, 5-nonanol, 1-decanol, 1-undecanol, and 1-dodecanol. 1-Heptanol was the shortest alcohol that formed an inclusion compound by the procedure employed. The ease of formation of a straight-chain alcohol was proportional to the number of uninterrupted methylene groups (-CH 2 -) present. The ease of urea inclusion compound formation generally decreases as the functional group approaches the center of the chain. These conclusions were based on X-ray powder diffraction measurements and the weight of recovered products under equilibrium conditions.