Structural information of long‐chain fatty material obtained rapidly and conveniently by the use of X‐ray diffraction studies of single crystals of urea and thiourea adducts

Abstract

AbstractX‐ray diffraction patterns of single crystals of urea or thiourea adducts of long chain fatty material (channel type of inclusion compounds) yield diffuse, continuous layer lines instead of the usual spots obtained with ordinary crystals. These lines result because adduct crystals have order in one dimension only, (the channel direction) whereas in ordinary crystals there is order in three dimensions which yields spots.These continuous layer lines offer possibilities for structure determination of the included molecule (guest). From their spacing, i.e., their distance from the equator, the length of the guest can be quickly calculated. This in turn can give information on 1) degree of branching, 2)cis‐trans isomerism if the substance is unsaturated, and 3) molecular weight of the guest. From an evaluation of the intensities of the various orders of the layer lines, the position of a substituent group (such as a methyl, hydroxyl or keto group) on the hydrocarbon chain of the guest can be determined.