AbstractThe nuclear magnetic spin‐lattice relaxation time,T1, of 1,4‐paradioxane in deuterated 1,4‐paradioxane, deuterated chloroform, deuterated cyclohexane, deuterated benzene, and carbon tetrachloride was determined as a function of concentration and temperature over the temperature range of 10°C – 100°C. It was found that the rotational correlation time of the p‐dioxane molecule in infinitely dilute CDCl3solution was significantly longer than in the other four solvents. In particular it was found that when the rotational correlation time of the p‐dioxane molecule measured at 20°C in CDCl3solution was‐corrected for the difference in the viscosities of CDCl3and p‐dioxane there resulted a corrected rotational correlation time of 17·10−12s. This value is in fair agreement with the dielectric relaxation time of the CHCl3molecule in infinitely dilute p‐dioxane solution reported by Antony and Smyth [1], viz. 16.5 · 10−12sat 20°C. It was also found that the activation energy for molecular reorientation, ΔEτof the p‐dioxane molecule in infinitely dilute CDCl3was significantly higher than the activation energy for viscous flow, ΔEηin CHCl3, viz. 2.6 kcal/mol and 1.8 kcal/mol respectively. On the other hand it was found that in the case of the other four solvents ΔEτ, ≤ ΔEeta. It is suggested that the experimental results are best interpreted in terms of the formation of a complex between p‐dioxane and CDCl3mo