Conformational studies on hexahelicenes—I: The NMR spectra of the benzohexahelicenes |
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Authors: | W.H. Laarhoven And R.J.F. Nivard |
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Affiliation: | Department of Organic Chemistry, Catholic University, Toernooiveld, Nijmegen The Netherlands |
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Abstract: | The NMR spectra of the benzohexahelicenes have been analyzed. The conformation of the helical structure is not changed to a large extent by the benzo-groups. Some flattening of a part of the helix results in a small downfield shift of the protons on the terminal rings and in a larger upfield shift of proton A in II ascribed to a change in the ring current in the pitch of the helix. A gradual upfield shift is found for protons of the terminal rings by an increase in overcrowding of the benzo-groups. |
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