Sly, William Glenn (1955) I. The crystal structure of oxamide. II. The crystal structure of 15, 15'-dehydrobetacarotene. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-01262004-143104
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
A two-dimensional trial structure has been determined for oxamide by means of a Patterson projection. The analysis, which was the reinvestigation of a previous preliminary survey that had reported a slightly wavy planar structure with a 1.65 [Angstrom] C-C bond, was interrupted by the publication of an apparently satisfactory structure by Romers. The present study and two recent publications are in agreement both as to the parameters and space group of the triclinic unit cell, and the configuration of the molecule. The oxamide molecules are centered and they are hydrogen bonded into an essentially planar sheet which is parallel to the almost perfect cleavage plane exhibited by the crystals. The dimensions indicate that the C-C bond is a pure single bond and that the C-N bond has about 50% double-bond character as a result of resonance in the amide group. Oxamide, like oxalic acid and a few other related substances, is planar although the C-C bond apparently has no double-bond character.
The crystal structure of 15,15'-dehydrobetacarotene has been determined; this analysis represents the first conclusive study of any carotenoid. The analysis was accomplished through the use of a three-dimensional Patterson coupled with trial and error methods, and has been carried to a moderate state of refinement with Fourier projections, two-dimensional least squares, and a three-dimensional Fourier. The monoclinic unit cell has the parameters [...], [...], [...], and [...]; the space group is uniquely determined to be [...], which requires that the two molecules in the unit cell be centered. Except for the cyclohexene rings, the molecule is essentially plane with bond lengths and angles in general agreement with those predicted by theory and experiment. The chains are packed together almost unaffected by the cyclohexene rings. Each ring has the cis orientation about the single bond from ring to chain; the molecule is otherwise all trans. The molecules are efficiently packed, but the arrangement has resulted in a loss of resonance energy since the rings are not coplanar with the chain. The hypersymmetry of the molecules accounts for the deviation of the intensities from a normal statistical distribution.
A brief discussion of some of the IBM techniques used in the refinement of this structure has been included in the appendix.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Division:||Chemistry and Chemical Engineering|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||1 January 1955|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||29 Jan 2004|
|Last Modified:||26 Dec 2012 02:29|
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