The equation is a cosine series in 8, the torsion angle between vicinal hydrogens. The feature which distinguishes this equation from similar equations is the inclusion of ASi terms, which describe the magnitude of each substituent's effect. These substituent constants have been defined from experimental data. An orientation effect which is dependent on the torsion angle(s) between substituent(s) and a vicinal hydrogen is included. Substituent constants have been defined for 39 groups, of which 15 have been experimentally determined herein. The parameters for the equation have been defined from 49 torsion angles in 19 conformationally rigid compounds. The torsion angles have been determined from x-ray crystal structure data and molecular mechanics calculations. The multiplicity of structures used to determine the substituent constants should allow for the application of this equation to a wide variety of structures.
Catalysis of ester aminolysis by cyclic and acyclic polyethers reported from this laboratory2 has served as an encouragement to examine polyether catalysis in other reactions of amines as well as to develop new polyethers. Recently, syntheses of crown ethers with functionalized side chains (lariat ethers3) have been reported.3"7 In particular, alkoxymethyl-substituted crown ethers have attracted considerable attention as synthons for more complex macrocycles and polymer-supported crowns.4,7"11
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