Conformational studies on oligo‐<i>l</i>‐<i>iso</i>‐butylethyleneurethans. Oligourethan. VII

<jats:title>Abstract</jats:title><jats:p>The conformations of oligo‐<jats:italic>l</jats:italic>‐<jats:italic>iso</jats:italic>‐butylethyleneurethans, <jats:disp-formula> </jats:disp-formula> (L‐form, n = 1–7), in various solvents were studied by optical rotatory dispersion and infrared spectroscopy.</jats:p><jats:p>All oligomers showed simple dispersion in solvents such as alcohols, cyclic ethers, <jats:italic>m</jats:italic>‐cresol, pyridine, chloroform, and tetrachloroethylene. On the other hand, the hexamer and heptamer showed anomalous dispersions in solvents such as benzene, toluene, and anisol, while lower homologues up to the pentamer showed simple dispersion in these solvents.</jats:p><jats:p>The anomalous dispersions were interpreted as a helix<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#note1" /><jats:fn><jats:p>The term “<jats:italic>helix</jats:italic>” used in this paper for oligourethans means an <jats:italic>ordered helical structure</jats:italic>, it does not mean an α‐<jats:italic>helix</jats:italic> of peptides.</jats:p></jats:fn> formation due to the intramolecular hydrogen bonding.</jats:p><jats:p>Small angle X‐ray analysis demonstrated that the observed long spacings of the oigomers agreed well with the calculated chain lengths based on the fully extended models.</jats:p>