Conformations and steric and stacking interactions of trisubstituted ureas and thioureas with alkyl and phenyl groups |
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Authors: | Yoshiyuki Mido Hiroko Okada Tamotsu Itoh |
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Affiliation: | Department of Chemistry, Faculty of Science, Kobe University, Nada,Kobe 657 Japan |
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Abstract: | The monomeric ν(N—H) vibrations of various trisubstituted ureas of the R2UPh type and -thioureas of the R2TUPh type have been studied. The trans—out isomerism in the former and the trans—out—cis isomerism in the latter are discussed from the point of view of steric effect. The monomeric ν(N—H) vibrations of RPhUPh and RPhTUPh are also examined. The single band appearing in the spectrum of both ureas is characteristic of the cis form; this suggests the existence of phenyl—phenyl interaction (the stacking interaction proposed by Galabov et al. [10]). Behavior of ν(N—H) vibrations at several concentrations is shown to be clearly different in the three forms (trans, out and cis). The presence of the cis form is confirmed by solvent effect experiments. |
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Keywords: | Present address: Examination Laboratory Waterworks Department of Osaka Prefectural Government Muranotakamidai Hirakata Osaka 573 Japan. |
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