N,N'-Dialkylureas, which form intermolecular hydrogen bonds, are interestin
g precursors in the field of supramolecular chemistry. Particularly, N,N'-d
i(2-ethylhexyl)urea, which is soluble in nonpolar solvents, was shown by vi
scosimetry and FTIR spectroscopy to be associated in heptane at concentrati
ons higher than 10 g l(-1). The interactions involved are strongly reinforc
ed by the cooperative association of two urea groups in the case of bis-ure
as prepared from 2,4-toluene diisocyanate.