Cotton effects in circular dichroism and optical rotatory dispersion spectra of 1,3-dienes and (alpha),(beta)-unsaturated ketones, for their (pi)-(pi)* transitions, are believed to arise from inherent dissymmetry of the chromophores as well as dissymmetric substituents. A selected number of chiral acyclic 1,3-dienes and (alpha),(beta)-unsaturatedaldehydes of the general structure shown were synthesized by routes thatwould also provide their absolute configurations. The chromophores in these molecules are believed to be transoidal and planar. Ultra violet and circular dichroism spectra were measured for these molecules and their longest wavelength (pi)-(pi)* Cotton effects interpreted in terms of contributions of dissymmetric substituents. A "Diene Sector Rule" has been proposed for chiral acyclic planar transoidal 1,3-dienes for their longest wavelength (pi)-(pi)* transition which would predict the absolute configurations of these molecules from their observed Cotton effects. The rule takes into account the chiral axes of the double bonds by placing the chromophore in a plane (A) and then drawing two parallel planes (B) and (C) perpendicular to plane (A) and passing through the individual double bonds. This leads to the formation of six sectors. Positive and negative signs have been assigned to each sector based on a chiral planar 1,3-diene of known absolute configuration and its observed Cotton effect assuming that a carbon-hydrogen bond makes a greater contribution to the Cotton effect than a carbon-carbon bond. The proposed rule is also applicable to chiral planar transoidal (alpha),(beta)-unsaturated aldehydes for their long wavelength (pi)-(pi)* transition. The rule was found valid for all the dienes and (alpha),(beta)-unsaturated aldehydes of known absolute configurations prepared for this study. The rule was also found applicable to natural and synthetic products containing a transoidal planar or nearly planar 1,3-diene or (alpha),(beta)-unsaturated ketone chromophore. / Source: Dissertation Abstracts International, Volume: 42-01, Section: B, page: 0211. / Thesis (Ph.D.)--The Florida State University, 1981.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_74399 |
| Creators | Duraisamy, Muthusamy |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text |
| Format | 156 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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